Support for Xtensa emitter and assembler, and upgraded F4 and F7 STM HAL

This release adds support for the Xtensa architecture as a target for the
native emitter, as well as Xtensa inline assembler.  The int.from_bytes
and int.to_bytes methods now require a second argument (the byte order)
per CPython (only "little" is supported at this time).  The "readall"
method has been removed from all stream classes that used it; "read" with
no arguments should be used instead.  There is now support for importing
packages from compiled .mpy files.  Test coverage is increased to 96%.

The generic I2C driver has improvements: configurable clock stretching
timeout, "stop" argument added to readfrom/writeto methods, "nack"
argument added to readinto, and write[to] now returns num of ACKs
received.  The framebuf module now handles 16-bit depth (generic colour
format) and has hline, vline, rect, line methods.  A new utimeq module is
added for efficient queue ordering defined by modulo time (to be
compatible with time.ticks_xxx functions).  The pyboard.py script has been
modified so that the target board is not reset between scripts or commands
that are given on a single command line.

For the stmhal port the STM Cube HAL has been upgraded: Cube F4 HAL to
v1.13.1 (CMSIS 2.5.1, HAL v1.5.2) and Cube F7 HAL to v1.1.2.  There is a
more robust pyb.I2C implementation (DMA is now disabled by default, can be
enabled via an option), and there is an implementation of machine.I2C with
robust error handling and hardware acceleration on F4 MCUs.  It is now
recommended to use machine.I2C instead of pyb.I2C.  The UART class is now
more robust with better handling of errors/timeouts.  There is also more
accurate VBAT and VREFINT measurements for the ADC.  New boards that are
supported include: NUCLEO_F767ZI, STM32F769DISC and NUCLEO_L476RG.

For the esp8266 port select/poll is now supported for sockets using the
uselect module.  There is support for native and viper emitters, as well
as an inline assembler (with limited iRAM for storage of native functions,
or the option to store code to flash).  There is improved software I2C
with a slight API change: scl/sda pins can be specified as positional only
when "-1" is passed as the first argument to indicate the use of software
I2C.  It is recommended to use keyword arguments for scl/sda.  There is
very early support for over-the-air (OTA) updates using the yaota8266
project.

A detailed list of changes follows.

py core:
- emitnative: fix native import emitter when in viper mode
- remove readall() method, which is equivalent to read() w/o args
- objexcept: allow clearing traceback with 'exc.__traceback__ = None'
- runtime: mp_resume: handle exceptions in Python __next__()
- mkrules.mk: rework find command so it works on OSX
- *.mk: replace uses of 'sed' with $(SED)
- parse: move function to check for const parse node to parse.[ch]
- parse: make mp_parse_node_new_leaf an inline function
- parse: add code to fold logical constants in or/and/not operations
- factor persistent code load/save funcs into persistentcode.[ch]
- factor out persistent-code reader into separate files
- lexer: rewrite mp_lexer_new_from_str_len in terms of mp_reader_mem
- lexer: provide generic mp_lexer_new_from_file based on mp_reader
- lexer: rewrite mp_lexer_new_from_fd in terms of mp_reader
- lexer: make lexer use an mp_reader as its source
- objtype: implement __call__ handling for an instance w/o heap alloc
- factor out common code from assemblers into asmbase.[ch]
- stream: move ad-hoc ioctl constants to stream.h and rename them
- compile: simplify configuration of native emitter
- emit.h: remove long-obsolete declarations for cpython emitter
- move arch-specific assembler macros from emitnative to asmXXX.h
- asmbase: add MP_PLAT_COMMIT_EXEC option for handling exec code
- asmxtensa: add low-level Xtensa assembler
- integrate Xtensa assembler into native emitter
- allow inline-assembler emitter to be generic
- add inline Xtensa assembler
- emitinline: embed entire asm struct instead of a pointer to it
- emitinline: move inline-asm align and data methods to compiler
- emitinline: move common code for end of final pass to compiler
- asm: remove need for dummy_data when doing initial assembler passes
- objint: from_bytes, to_bytes: require byteorder arg, require "little"
- binary: do zero extension when storing a value larger than word size
- builtinimport: support importing packages from compiled .mpy files
- mpz: remove unreachable code in mpn_or_neg functions
- runtime: zero out fs_user_mount array in mp_init
- mpconfig.h: enable MICROPY_PY_SYS_EXIT by default
- add MICROPY_KBD_EXCEPTION config option to provide mp_kbd_exception
- compile: add an extra pass for Xtensa inline assembler
- modbuiltins: remove unreachable code
- objint: rename mp_obj_int_as_float to mp_obj_int_as_float_impl
- emitglue: refactor to remove assert(0), to improve coverage
- lexer: remove unreachable code in string tokeniser
- lexer: remove unnecessary check for EOF in lexer's next_char func
- lexer: permanently disable the mp_lexer_show_token function
- parsenum: simplify and generalise decoding of digit values
- mpz: fix assertion in mpz_set_from_str which checks value of base
- mpprint: add assertion for, and comment about, valid base values
- objint: simplify mp_int_format_size and remove unreachable code
- unicode: comment-out unused function unichar_isprint
- consistently update signatures of .make_new and .call methods
- mkrules.mk: add MPY_CROSS_FLAGS option to pass flags to mpy-cross
- builtinimport: fix bug when importing names from frozen packages

extmod:
- machine_i2c: make the clock stretching timeout configurable
- machine_i2c: raise an error when clock stretching times out
- machine_i2c: release SDA on bus error
- machine_i2c: add a C-level I2C-protocol, refactoring soft I2C
- machine_i2c: add argument to C funcs to control stop generation
- machine_i2c: rewrite i2c.scan in terms of C-level protocol
- machine_i2c: rewrite mem xfer funcs in terms of C-level protocol
- machine_i2c: remove unneeded i2c_write_mem/i2c_read_mem funcs
- machine_i2c: make C-level functions return -errno on I2C error
- machine_i2c: add 'nack' argument to i2c.readinto
- machine_i2c: make i2c.write[to] methods return num of ACKs recvd
- machine_i2c: add 'stop' argument to i2c readfrom/writeto meths
- machine_i2c: remove trivial function wrappers
- machine_i2c: expose soft I2C obj and readfrom/writeto funcs
- machine_i2c: add hook to constructor to call port-specific code
- modurandom: allow to build with float disabled
- modframebuf: make FrameBuffer handle 16bit depth
- modframebuf: add back legacy FrameBuffer1 "class"
- modframebuf: optimise fill and fill_rect methods
- vfs_fat: implement POSIX behaviour of rename, allow to overwrite
- moduselect: use stream helper function instead of ad-hoc code
- moduselect: use configurable EVENT_POLL_HOOK instead of WFI
- modlwip: add ioctl method to socket, with poll implementation
- vfs_fat_file: allow file obj to respond to ioctl flush request
- modbtree: add method to sync the database
- modbtree: rename "sync" method to "flush" for consistency
- modframebuf: add hline, vline, rect and line methods
- machine_spi: provide reusable software SPI class
- modframebuf: make framebuf implement the buffer protocol
- modframebuf: store underlying buffer object to prevent GC free
- modutimeq: copy of current moduheapq with timeq support for refactoring
- modutimeq: refactor into optimized class
- modutimeq: make time_less_than be actually "less than", not less/eq

lib:
- utils/interrupt_char: use core-provided mp_kbd_exception if enabled

drivers:
- display/ssd1306.py: update to use FrameBuffer not FrameBuffer1
- onewire: enable pull up on data pin
- onewire/ds18x20: fix negative temperature calc for DS18B20

tools:
- tinytest-codegen: blacklist recently added uheapq_timeq test (qemu-arm)
- pyboard.py: refactor so target is not reset between scripts/cmd
- mpy-tool.py: add support for OPT_CACHE_MAP_LOOKUP_IN_BYTECODE

tests:
- micropython: add test for import from within viper function
- use read() instead of readall()
- basics: add test for logical constant folding
- micropython: add test for creating traceback without allocation
- micropython: move alloc-less traceback test to separate test file
- extmod: improve ujson coverage
- basics: improve user class coverage
- basics: add test for dict.fromkeys where arg is a generator
- basics: add tests for if-expressions
- basics: change dict_fromkeys test so it doesn't use generators
- basics: enable tests for list slice getting with 3rd arg
- extmod/vfs_fat_fileio: add test for constructor of FileIO type
- extmod/btree1: exercise btree.flush()
- extmod/framebuf1: add basics tests for hline, vline, rect, line
- update for required byteorder arg for int.from_bytes()/to_bytes()
- extmod: improve moductypes test coverage
- extmod: improve modframebuf test coverage
- micropython: get heapalloc_traceback test running on baremetal
- struct*: make skippable
- basics: improve mpz test coverage
- float/builtin_float_round: test round() with second arg
- basics/builtin_dir: add test for dir() of a type
- basics: add test for builtin locals()
- basics/set_pop: improve coverage of set functions
- run-tests: for REPL tests make sure the REPL is exited at the end
- basics: improve test coverage for generators
- import: add a test which uses ... in from-import statement
- add tests to improve coverage of runtime.c
- add tests to improve coverage of objarray.c
- extmod: add test for utimeq module
- basics/lexer: add a test for newline-escaping within a string
- add a coverage test for printing the parse-tree
- utimeq_stable: test for partial stability of utimeq queuing
- heapalloc_inst_call: test for no alloc for simple object calls
- basics: add tests for parsing of ints with base 36
- basics: add tests to improve coverage of binary.c
- micropython: add test for micropython.stack_use() function
- extmod: improve ubinascii.c test coverage
- thread: improve modthread.c test coverage
- cmdline: improve repl.c autocomplete test coverage
- unix: improve runtime_utils.c test coverage
- pyb/uart: update test to match recent change to UART timeout_char
- run-tests: allow to skip set tests
- improve warning.c test coverage
- float: improve formatfloat.c test coverage using Python
- unix: improve formatfloat.c test coverage using C
- unix/extra_coverage: add basic tests to import frozen str and mpy
- types1: split out set type test to set_types
- array: allow to skip test if "array" is unavailable
- unix/extra_coverage: add tests for importing frozen packages

unix port:
- rename define for unix moduselect to MICROPY_PY_USELECT_POSIX
- Makefile: update freedos target for change of USELECT config name
- enable utimeq module
- main: allow to print the parse tree in coverage build
- Makefile: make "coverage_test" target mirror Travis test actions
- moduselect: if file object passed to .register(), return it in .poll()
- Makefile: split long line for coverage target, easier to modify
- enable and add basic frozen str and frozen mpy in coverage build
- Makefile: allow cache-map-lookup optimisation with frozen bytecode

windows port:
- enable READER_POSIX to get access to lexer_new_from_file

stmhal port:
- dma: de-init the DMA peripheral properly before initialising
- i2c: add option to I2C to enable/disable use of DMA transfers
- i2c: reset the I2C peripheral if there was an error on the bus
- rename mp_hal_pin_set_af to _config_alt, to simplify alt config
- upgrade to STM32CubeF4 v1.13.0 - CMSIS/Device 2.5.1
- upgrade to STM32CubeF4 v1.13.0 - HAL v1.5.1
- apply STM32CubeF4 v1.13.1 patch - upgrade HAL driver to v1.5.2
- hal/i2c: reapply HAL commit ea040a4 for f4
- hal/sd: reapply HAL commit 1d7fb82 for f4
- hal: reapply HAL commit 9db719b for f4
- hal/rcc: reapply HAL commit c568a2b for f4
- hal/sd: reapply HAL commit 09de030 for f4
- boards: configure all F4 boards to work with new HAL
- make-stmconst.py: fix regex's to work with current CMSIS
- i2c: handle I2C IRQs
- dma: precalculate register base and bitshift on handle init
- dma: mark DMA sate as READY even if HAL_DMA_Init is skipped
- can: clear FIFO flags in IRQ handler
- i2c: provide custom IRQ handlers
- hal: do not include <stdio.h> in HAL headers
- mphalport.h: use single GPIOx->BSRR register
- make-stmconst.py: add support for files with invalid utf8 bytes
- update HALCOMMITS due to change to hal
- make-stmconst.py: restore Python 2 compatibility
- update HALCOMMITS due to change to hal
- moduselect: move to extmod/ for reuse by other ports
- i2c: use the HAL's I2C IRQ handler for F7 and L4 MCUs
- updates to get F411 MCUs compiling with latest ST HAL
- i2c: remove use of legacy I2C_NOSTRETCH_DISABLED option
- add beginnings of port-specific machine.I2C implementation
- i2c: add support for I2C4 hardware block on F7 MCUs
- i2c: expose the pyb_i2c_obj_t struct and some relevant functions
- machine_i2c: provide HW implementation of I2C peripherals for F4
- add support for flash storage on STM32F415
- add back GPIO_BSRRL and GPIO_BSRRH constants to stm module
- add OpenOCD configuration for STM32L4
- add address parameters to openocd config files
- adc: add "mask" selection parameter to pyb.ADCAll constructor
- adc: provide more accurate measure of VBAT and VREFINT
- adc: make ADCAll.read_core_temp return accurate float value
- adc: add ADCAll.read_vref method, returning "3.3v" value
- adc: add support for F767 MCU
- adc: make channel "16" always map to the temperature sensor
- sdcard: clean/invalidate cache before DMA transfers with SD card
- moduos: implement POSIX behaviour of rename, allow to overwrite
- adc: use constants from new HAL version
- refactor UART configuration to use pin objects
- uart: add support for UART7 and UART8 on F7 MCUs
- uart: add check that UART id is valid for the given board
- cmsis: update STM32F7 CMSIS device include files to V1.1.2
- hal: update ST32CubeF7 HAL files to V1.1.2
- port of f4 hal commit c568a2b to updated f7 hal
- port of f4 hal commit 09de030 to updated f7 hal
- port of f4 hal commit 1d7fb82 to updated f7 hal
- declare and initialise PrescTables for F7 MCUs
- boards/STM32F7DISC: define LSE_STARTUP_TIMEOUT
- hal: update HALCOMMITS due to change in f7 hal files
- refactor to use extmod implementation of software SPI class
- cmsis: add CMSIS file stm32f767xx.h, V1.1.2
- add NUCLEO_F767ZI board, with openocd config for stm32f7
- cmsis: add CMSIS file stm32f769xx.h, V1.1.2
- add STM32F769DISC board files
- move PY_SYS_PLATFORM config from board to general config file
- mpconfigport: add weak-module links for io, collections, random
- rename mp_const_vcp_interrupt to mp_kbd_exception
- usb: always use the mp_kbd_exception object for VCP interrupt
- use core-provided keyboard exception object
- led: properly initialise timer handle to zero before using it
- mphalport.h: explicitly use HAL's GPIO constants for pull modes
- usrsw: use mp_hal_pin_config function instead of HAL_GPIO_Init
- led: use mp_hal_pin_config function instead of HAL_GPIO_Init
- sdcard: use mp_hal_pin_config function instead of HAL_GPIO_Init
- add support for STM32 Nucleo64 L476RG
- uart: provide a custom function to transmit over UART
- uart: increase inter-character timeout by 1ms
- enable utimeq module

cc3200 port:
- tools/smoke.py: change readall() to read()
- pybspi: remove static mode=SPI.MASTER parameter for latest HW API
- mods/pybspi: remove SPI.MASTER constant, it's no longer needed
- update for moduselect moved to extmod/
- re-add support for UART REPL (MICROPY_STDIO_UART setting)
- enable UART REPL by default
- README: (re)add information about accessing REPL on serial
- make: rename "deploy" target to "deploy-ota"
- add targets to erase flash, deploy firmware using cc3200tool
- README: reorganize and update to the current state of affairs
- modwlan: add network.WLAN.print_ver() diagnostic function

esp8266 port:
- enable uselect module
- move websocket_helper.py from scripts to modules for frozen BC
- refactor to use extmod implementation of software SPI class
- mpconfigport_512k: disable framebuf module for 512k build
- enable native emitter for Xtensa arch
- enable inline Xtensa assembler
- add "ota" target to produce firmware binary for use with yaota8266
- use core-provided keyboard exception object
- add "erase" target to Makefile, to erase entire flash
- when doing GC be sure to trace the memory holding native code
- modesp: flash_user_start(): support configuration with yaota8266
- force relinking OTA firmware image if built after normal one
- scripts/inisetup: dump FS starting sector/size on error
- Makefile: produce OTA firmware as firmware-ota.bin
- modesp: make check_fw() work with OTA firmware
- enable utimeq module
- Makefile: put firmware-ota.bin in build/, for consistency
- modules/flashbdev: add RESERVED_SECS before the filesystem
- modules/flashbdev: remove code to patch bootloader flash size
- modules/flashbdev: remove now-unused function set_bl_flash_size
- modules/flashbdev: change RESERVED_SECS to 0

zephyr port:
- add .gitignore to ignore Zephyr's "outdir" directory
- zephyr_getchar: update to Zephyr 1.6 unified kernel API
- switch to Zephyr 1.6 unified kernel API
- support raw REPL
- implement soft reset feature
- main: initialize sys.path and sys.argv
- use core-provided keyboard exception object
- uart_core: access console UART directly instead of printk() hack
- enable slice subscription

docs:
- remove references to readall() and update stream read() docs
- library/index: elaborate on u-modules
- library/machine.I2C: refine definitions of I2C methods
- library/pyb.Accel: add hardware note about pins used by accel
- library/pyb.UART: added clarification about timeouts
- library/pyb.UART: moved writechar doc to sit with other writes
- esp8266/tutorial: update intro to add Getting the firmware section
- library/machine.I2C: fix I2C constructor docs to match impl
- esp8266/tutorial: close socket after reading page content
- esp8266/general: add "Scarcity of runtime resources" section
- library/esp: document esp.set_native_code_location() function
- library/esp: remove para and add further warning about flash
- usocket: clarify that socket timeout raises OSError exception

travis:
- build STM32 F7 and L4 boards under Travis CI
- include persistent bytecode with floats in coverage tests

examples:
- hwapi: button_led: Add GPIO pin read example
- hwapi: add soft_pwm example converted to uasyncio
- http_client: use read() instead of readall()
- hwapi: add uasyncio example of fading 2 LEDs in parallel
- hwapi: add example for machine.time_pulse_us()
- hwapi: add hwconfig for console tracing of LED operations
- accellog.py: change 1: to /sd/, and update comment about FS
- hwapi/hwconfig_console: don't alloc memory in value()

ESP8266 port uses SDK 2.0, has more heap, has support for 512k devices

This release brings some code size reductions to the core as well as
more tests and improved coverage which is now at 94.3%.

The time.ticks_diff(a, b) function has changed: the order of the arguments
has been swapped so that it behaves like "a - b", and it can now return a
negative number if "a" came before "b" (modulo the period of the ticks
functions).

For the ESP8266 port the Espressif SDK has been updated to 2.0.0, the
heap has been increased from 28k to 36k, and there is support for 512k
devices via "make 512k".  upip is included by default as frozen bytecode.
The network module now allows access-point reconnection without WiFi
credentials, and exposes configuration for the station DHCP hostname.  The
DS18B20 driver now handles negative temperatures, and NeoPixel and APA102
drivers handle 4 bytes-per-pixel LEDs.

For the CC3200 port there is now support for loading of precompiled .mpy
files and threading now works properly with interrupts.

A detailed list of changes follows.

py core:
- py.mk: automatically add frozen.c to source list if FROZEN_DIR is defined
- be more specific with MP_DECLARE_CONST_FUN_OBJ macros
- specialise builtin funcs to use separate type for fixed arg count
- {modbuiltins,obj}: use MP_PYTHON_PRINTER where possible
- modbuiltins: add builtin "slice", pointing to existing slice type
- add "delattr" builtin, conditional on MICROPY_CPYTHON_COMPAT
- sequence: fix reverse slicing of lists
- fix null pointer dereference in mpz.c, fix missing va_end in warning.c
- remove asserts that are always true in emitbc.c
- fix wrong assumption that m_renew will not move if shrinking
- change config default so m_malloc0 uses memset if GC not enabled
- add MICROPY_FLOAT_CONST macro for defining float constants
- move frozen bytecode Makefile rules from ports to common mk files
- strip leading dirs from frozen mpy files, so any path can be used

extmod:
- vfs_fat_file: check fatfs f_sync() and f_close() returns for errors
- vfs_fat_file: make file.close() a no-op if file already closed
- utime_mphal: ticks_diff(): switch arg order, return signed value
- utime_mphal: add MP_THREAD_GIL_EXIT/ENTER warppers for sleep functions
- utime_mphal: implement ticks_add(), add to all maintained ports
- utime_mphal: allow ticks functions period be configurable by a port

lib:
- utils/pyhelp.c: use mp_printf() instead of printf()
- utils/pyexec: add mp_hal_set_interrupt_char() prototype
- libm: move Thumb-specific sqrtf function to separate file

drivers:
- add "from micropython import const" when const is used

tools:
- upgrade upip to 1.1.4: fix error on unix when installing to non-existing
  absolute path
- pip-micropython: remove deprecated wrapper tool
- check_code_size.sh: code size validation script for CI
- replace upip tarball with just source file, to make its inclusion as
  frozen modules in multiple ports less magic

tests:
- extmod/vfs_fat: improve VFS test coverage
- basics/builtin_slice: add test for "slice" builtin name
- basics: add test for builtin "delattr"
- extmod/vfs_fat_fsusermount: improve fsusermount test coverage
- extmod/vfs_fat_oldproto: test old block device protocol
- basics/gc1: garbage collector threshold() coverage
- extmod/uhashlib_sha1: coverage for SHA1 algorithm
- extmod/uhashlib_sha256: rename sha256.py test
- btree1: fix out of memory error running on esp8266
- extmod/ticks_diff: test for new semantics of ticks_diff()
- extmod/framebuf1: test framebuffer pixel clear, and text function

minimal port:
- Makefile: split rule for firmware.bin generation

unix port:
- Makefile: remove references to deprecated pip-micropython
- modtime: use ticks_diff() implementation from extmod/utime_mphal.c
- mphalport.h: add warning of mp_hal_delay_ms() implementation
- modtime: switch ticks/sleep_ms/us() to utime_mphal
- fix symbol references for x86 Mac
- replace upip tarball with just source file

windows port:
- enable utime_mphal following unix, define mp_hal_ticks_*
- fix utime_mphal compilation for msvc
- implement mp_hal_ticks_cpu in terms of QueryPerformanceCounter

qemu-arm port:
- exclude ticks_diff test for qemu-arm port
- exclude extmod/vfs_fat_fileio.py test
- exclude new vfs_fat tests
- enable software floating point support, and float tests

stmhal port:
- modutime: refactor to use extmod's version of ticks_cpu
- refactor pin usage to use mp_hal_pin API
- led: refactor LED to use mp_hal_pin_output() init function
- Makefile: use standard rules for frozen module generation
- modutime: consistently convert to MP_ROM_QSTR/MP_ROM_PTR
- enable SD power save (disable CLK on idle)

cc3200 port:
- use mp_raise_XXX helper functions to reduce code size
- mods/pybspi: allow "write" arg of read/readinto to be positional
- enable loading of precompiled .mpy files
- fix thread mutex's so threading works with interrupts

teensy port:
- update to provide new mp_hal_pin_XXX functions following stmhal

esp8266 port:
- Makefile: use latest esptool.py flash size auto-detection
- esp_init_data: auto-initialize system params with vendor SDK 2.0.0
- esp8266.ld: move help.o to iROM
- esp8266.ld: move modmachine.o to iROM
- esp8266.ld: move main.o to iROM
- add MP_FASTCODE modifier to put a function to iRAM
- main: mark nlr_jump_fail() as MP_FASTCODE
- modules/webrepl: enforce only one concurrent WebREPL connection
- etshal.h: add few more ESP8266 vendor lib prototypes
- modesp: add flash_user_start() function
- add support for building firmware version for 512K modules
- scripts: make neopixel/apa102 handle 4bpp LEDs with common code
- modutime: consistently convert to MP_ROM_QSTR/MP_ROM_PTR
- modnetwork: config(): fix copy-paste error in setting "mac"
- scripts/port_diag: add descriptions for esf_buf types
- modnetwork.c: allows AP reconnection without WiFi credentials
- main: bump heap size to 36K
- etshal.h: add prototypes for SPIRead/SPIWrite/SPIEraseSector
- etshal.h: adjust size of MD5_CTX structure
- modules: fix negative temperature in ds18x20 driver
- rename "machine" module implementation to use contemporary naming
- rework webrepl_setup to run over wired REPL
- espneopixel.c: solve glitching LED issues with cpu at 80MHz
- include upip as a standard frozen bytecode module
- update docs for esptool 1.2.1/SDK 2.0 (--flash_size=detect)
- modnetwork.c: expose configuration for station DHCP hostname

zephyr port:
- implement utime module
- use board/SoC values for startup banner based on Zephyr config
- initial implementation of machine.Pin
- zephyr_getchar: update for recent Zephyr refactor of console hooks
- support time -> utime module "weaklink"
- README: update for the current featureset, add more info
- mpconfigport.h: move less important params to the bottom
- Makefile: allow to adjust heap size from make command line
- Makefile: update comments to the current state of affairs
- Makefile: allow to override Zephyr config from make command line
- Makefile: add minimal port
- Makefile: add -fomit-frame-pointer to reduce code size
- mphalport.h: update for new "unified" kernal API (sleep functions)

docs:
- machine.SPI: bring up to date with Hardware API, make vendor-neutral
- machine.SPI: improve descriptions of xfer methods
- library/builtins: add docs for delattr and slice
- library/network: reword intro paragraph
- library/network: typo fixes, consistent acronym capitalization
- library/index: update TOCs so builtins sorted before modules
- utime: document ticks_cpu() in more detail
- utime: describe new semantics of ticks_diff() (signed ring arithmetics)
- utime: add docs for ticks_add(), improvements for other ticks_*()
- esp8266: update for new WebREPL setup procedure
- */quickref.rst: use new semantics of ticks_diff()
- library/machine.Pin: update Pin docs to align with new HW API

travis:
- integrate tools/check_code_size.sh
- minimal: Use CROSS=1, for binary size check

examples:
- http_server_simplistic: add "not suitable for real use" note
- hwapi: example showing best practices for HW API usage in apps
- hwapi: add hwconfig for DragonBoard 410c

New port to Zephyr, upip runs on baremetal, and reduction in code size

This release adds a new port of MicroPython to run on top of the Zephyr
real-time operating system.  As part of this there is now basic support for
using mbedTLS as the ussl module.  The release also brings initial support
for running the package manager upip on baremetal systems with low heap
memory (such as esp8266), through a Python module interface.

Work has been done in this release to clean up the core, removing redundant
and/or unreachable code, and factoring existing duplicated code patterns.
This brings a reduction of 828 bytes in code size to the bare-arm port, and
1368 bytes to the minimal port.  There is also improved coverage through
the addition of new tests for corner cases.

The "micropython" module sees the addition of the "const" identity function
which should be used as "from micropython import const" in scripts that
want to use the MicroPython constant optimisations in the compile stage.
There is also the addition of the "opt_level" function to change the
parser/compiler optimisation level at runtime.

The behaviour of "sys.exit" (and "raise SystemExit") on baremetal is now
changed: this function no longer does a soft-reset of the board, rather it
just stops the running script and drops to the REPL.  In order to do an
actual soft reset the "machine.soft_reset" function has been added (to the
stmhal port only, for the time being).

Following CPython, KeyError exceptions for dictionary lookups now have the
failed key stored as the argument of the exception instance, accessible as
exc.args[0].  The "ujson.load" function has also been added, to load JSON
data from an arbitrary stream.

The I2C support in the machine module now has clock stretching, the
addition of the "addrsize" parameter in memory transfer methods, and I2C
scanning now uses dummy writes instead of dummy reads to make the scanning
more reliable.

The CMSIS library has been upgrade to v4.30, and the boards section of
the stmhal port has been refactored to use a common.ld script.  The stmhal
port now has a full implementation of the machine.SPI class, with support
for both hardware SPI peripherals and fast software SPI.  The USB HID
driver in stmhal has added support to receive USB HID messages from the
host.

py core:
- asmthumb: flush D-cache, and invalidate I-cache on STM32F7
- makeqstrdefs.py: use python 2.6 syntax for set creation
- objnone: remove unnecessary handling of MP_UNARY_OP_BOOL
- move frozen modules rules from esp8266 port for reuse across ports
- combine 3 comprehension emit functions (list/dict/set) into 1
- combine 3 comprehension opcodes (list/dict/set) into 1
- vstr: remove vstr.had_error flag and inline basic vstr functions
- objnone: use mp_generic_unary_op instead of custom one
- showbc: make printf's go to the platform print stream
- remove 'name' member from mp_obj_module_t struct
- builtinimport: fix nanbox build after change to better handle -m modules
- stream: remove unnecessary check for NULL return from vstr_extend
- py.mk: suppress some compiler warnings when building berkeley-db
- shrink mp_arg_t struct by using reduced-size integer members
- update opcode format table because 3 opcodes were removed, 1 added
- parse: only replace constants that are standalone identifiers
- py.mk: add support for building modussl_mbedtls
- only store the exception instance on Py stack in bytecode try block
- vm: use MP_OBJ_FROM_PTR to cast a type to an object
- modmicropython: add micropython.const, alias for identity function
- objstr: remove unreachable function used only for terse error msgs
- emitbc: remove/refactor unreachable code, to improve coverage
- objfun: remove unnecessary check for viper fun with 5 or more args
- objfun: use if instead of switch to check return value of VM execute
- objset: use mp_check_self() to check args of set/frozenset methods
- objset: ensure that use of frozenset.update raises an exception
- compile: fix async-for/async-with to work with simpler exc on stack
- scope: use lookup-table to determine a scope's simple name
- scope: shrink scope_t struct by 1 machine word
- scope: factor common code to find locals and close over them
- compile: fix typo when checking for parse-node kind
- argcheck: simplify if-chain so that the last one is the default
- objbool: defer bool's unary op implementation to small int
- objbool: make a slight simplification of bool constructor
- modstruct: remove unreachable code, and add comment about CPy diff
- add mp_raise_OSError(errno) helper function
- objstringio: add readinto() method
- modmicropython: add micropython.opt_level([value]) function
- compile: remove unreachable code
- mpz: in divmod, replace check for rhs!=0 with assert
- mpz: use assert to verify mpz does not have a fixed digit buffer
- factor duplicated function to calculate size of formatted int
- objint: use size_t for arguments that measure bytes/sizes
- compile: remove debugging code for compiler dispatch
- lexer: remove unnecessary code, and unreachable code
- vstr: combine vstr_new_size with vstr_new since they are rarely used
- objdict: fix optimisation for allocating result in fromkeys
- objdict: actually provide the key that failed in KeyError exception
- use mp_raise_msg helper function where appropriate
- add the module specified by -m to sys.modules as '__main__'

extmod:
- modussl_mbedtls: initial implementation of mbedTLS ussl module
- uctypes: allow full 32-bit address range
- modubinascii: fix crc32() function on 32-bit platforms
- modussl_mbedtls: implement key= and cert= args to wrap_socket()
- modussl_mbedtls: use 2-component include paths
- machine_i2c: add clock stretching support
- modussl_mbedtls: add server_hostname param for wrap_socket()
- uzlib: add tinfgzip.c (gzip header parsing) from upstream
- moduzlib: DecompIO: Add support for gzip-formatted streams
- uzlib/: update uzlib to v2.0.3
- vfs_fat: add fat_vfs_statvfs(), reused from stmhal
- machine_i2c: add support for the addrsize parameter in mem xfers
- machine_spi: simplify SPI xfer function to only take one buf len
- machine_spi: factor out software SPI code from esp8266 to extmod
- machine_spi: use delay_half, not baudrate, for internal timing
- machine_spi: add optional support for fast software SPI
- vfs_fat: use mp_raise_OSError helper function
- modlwip: use mp_raise_OSError helper function
- use mp_raise_OSError helper function
- vfs_fat_file: use MP_Exxx errno constants
- uzlib: update to upstream v2.1
- machine_i2c: use writes not reads in i2c.scan()
- vfs_fat: add file and directory checks for remove and rmdir
- modujson: implement ujson.load() to load JSON from a stream
- modujson: fix nanbox build
- utime_mphal: factor out implementations in terms of mp_hal_* for reuse
- utime_mphal: sleep_us/ms(): Don't wait on negative argument
- modussl_mbedtls: add dummy setblocking() method

lib:
- interrupt_char: factor out typical Ctrl+C handling from esp8266 port
- cmsis: move CMSIS headers to lib/
- cmsis: remove CMSIS-DSP headers, they are unused
- cmsis: upgrade CMSIS-CORE to V4.30
- utils/pyexec: don't treat SystemExit as "forced exit"
- utils/pyexec: allow behaviour of SystemExit to be configurable

drivers:
- dht: use mp_raise_OSError helper function

tools:
- update upip to 0.8, fixes IPv6 support
- upgrade upip to 1.0, fully self-hosted release (without fallbacks), and
  uses stream gzip decompression (step towards support for limited-heap
  baremetal systems)
- upgrade upip to 1.1.3, initial support for running on a baremetal,
  low-heap systems (like esp8266), using Python module interface

tests:
- pyb: add test for ExtInt when doing swint while disabled
- pyb: update exp file for previously updated extint test
- extmod/urandom: add urandom tests for error cases
- basics: add errno1 test, to check basics of uerrno module
- extmod: add test for machine.time_pulse_us()
- struct1: test "l" specifier to improve coverage
- array1: add tests for "l", "L" array types to improve coverage
- get cmdline verbose tests running again
- run-tests: add --via-mpy option to run test from precompiled code
- uzlib_decompio_gz: test for DecompIO with gzip bitstream
- basics: add test case for overflowing Py stack in try-finally
- micropython: add tests for const names being replaced in parser
- cmdline/cmd_showbc: fix test now that 1 value is stored on stack
- extmod/vfs_fat_ramdisk: add test for VFS.statvfs()
- float: add test for parsing a float from an empty string
- basics: add test for set.difference_update with arg being itself
- basics: add further tests for nonlocal scoping and closures
- import: add test for compiling "import a.b as c"
- basics: add test constructing a set from a non-trivial expression
- basics: add test for printing OSError when errno is unknown
- run-tests: disable cmdline/cmd_showbc test on Windows
- extmod/btree1: checks for put, seq, string print and unsupported binary op
- fix expected output of verbose cmdline test
- extmod/uzlib: test adaptive huffman tree for tinflate coverage
- improve coverage of struct with test for non-compliant behaviour
- io/write_ext: add description comment
- io/bytesio_ext: add test for readinto()
- micropython: add test for micropython.opt_level() function
- improve test coverage of py/compile.c
- extmod/vfs_fat: test coverage for remove() and rmdir()
- extmod: add test for ujson.load()
- extmod/vfs_fat: replace asserts with prints and expected outputs
- micropython: add tests for heap_lock, and emergency exceptions
- cmdline: improve coverage test for printing bytecode
- improve coverage of array, range, dict, slice, exc, unicode
- add test to print full KeyError exc from failed dict lookup
- run-tests: enable extmod/machine1.py on pyboard

unix port:
- fix build for when MICROPY_PY_SOCKET=0
- modjni: implement subscription for object arrays
- modjni: add array() top-level function to create Java array
- modjni: array(): Support creation of object arrays
- enable btree module for coverage build
- use mp_raise_OSError helper function
- use common RAISE_ERRNO macro from mphalport.h

windows port:
- enable MICROPY_PY_UERRNO

qemu-arm port:
- enable lots of extmods and enable tests for them

stmhal port:
- lcd: de-assert chip select after completing SPI transmission
- {accel,lcd}: use GPIO_{set,clear}_pin
- extint: force 0 to 1 transition on swint()
- boards: add pllvalues.py script to compute PLL values for sysclk
- boards: for OLIMEX_E407, enable UART1 and fix I2C1 mapping
- use attribute to avoid inlining
- put common definitions from linker files to common.ld
- remove STM32CubeF2 HAL files, they are unused/unsupported
- modmachine: fix clearing of reset-cause flags
- add virtual com port support for STM32L476DISC
- remove CMSIS STM32F2xx files, they are unused/unsupported
- spi: simplify spi_transfer function to take only one buf len arg
- mphalport: implement mp_hal_pin_{input,output,write}
- spi: make machine.SPI class conform to correct API
- mphalport: fix mp_hal_pin_write to use correct pin_mask
- spi: use software SPI if no periph id given, even if pins given
- spi: enable use of fast software SPI
- fix linker map for STM32L476 chips
- usbdev: add OUT endpoint to HID interface
- usb: add support to receive USB HID messages from host
- usb: use correct ClassData structure for HID receive
- usb: use real packet size (not maximum) in HID receive
- fix ESPRUINO_PICO by adding ld scripts with correct flash size
- mphalport: change pin obj type to const pointer, to avoid casts
- moduos: implement total-number-of-blocks field in statvfs
- disable network and usocket for ESPRUINO_PICO
- enable machine.time_pulse_us() function
- use mp_raise_OSError helper function
- pybstdio: use size_t instead of mp_uint_t
- modutime: refactor to use extmod/utime_mphal.c
- implement machine.soft_reset()
- enable str.center(), str.[r]partition() and builtin compile()

cc3200 port:
- add ssl_version argument to ssl.wrap_socket()

esp8266 port:
- Makefile: rename SCRIPTDIR to FROZEN_DIR for consistency with FROZEN_MPY_DIR
- ets_alt_task: ets_post: Should return 0 on success, !0 - failure
- esp_mphal: add tentative change to mp_hal_stdin_rx_chr() to wait IRQ
- extend system microsecond counter to 64-bits; use in ticks_ms
- add uos.statvfs() to get filesystem status
- moduos: move stat/statvfs funcs to sit within #if VFS guard
- modmachine: idle(): Return number of CPU cycles spent idling
- main: put /lib before / in sys.path
- modpybrtc.c: implement machine.RTC.alarm_left()
- make PY_UHASHLIB_SHA1 config depend on PY_USSL and SSL_AXTLS
- add FLASH_MODE,FLASH_SIZE options for make deploy target
- use mp_raise_OSError helper function
- make neopixel support configurable
- mpconfigport: enable MICROPY_PY_BUILTINS_SLICE_ATTRS
- enable sys.{stdin,stdout,stderr}.buffer for raw serial access
- enable importing of precompiled .mpy files
- enable micropython.alloc_emergency_exception_buf()

zephyr port:
- initial Zephyr RTOS port, MicroPython part
- initial Zephyr RTOS port, Zephyr part
- add zephyr_getchar module to handle console input
- switch to microkernel, required for network to work in background
- automatically derive ARCH
- support extra make targets
- Makefile: automatically derive target-specific CFLAGS
- use recently added "make outputexports" Zephyr target
- add README
- enable stack checking and micropython.mem_info()
- enable frozen modules support
- main: execute main.py frozen module on boot, if available
- zephyr_getchar: add support for Ctrl+C handling
- add Ctrl+C handling
- implement the help() function
- add copyright blurbs

README:
- remove issue-stats badges, the service is no longer available
- mention _thread module availability in select ports

docs:
- library/pyb.SPI: init(): describe "bits" argument
- library/machine: update description of disable/enable IRQ funcs
- uos: add uos.statvfs() documentation
- wipy: correct deep sleep current figure
- wipy: small doc fixes
- reference: add constrained.rst doc

travis:
- abandon mingw32 in favour of mingw-w64
- run feature and coverage test for precompiled mpy files

examples:
- network/http_client*: use \r\n line-endings in request

Support for stream decompression in uzlib, and more ESP8266 features

This release includes some bug fixes, code clean-up, updates to the docs,
more tests, and various feature additions.  The uzlib module now supports
efficient stream decompression in the form of the uzlib.DecompIO class.
Freezing of bytecode now supports floats for the ESP8266 port, as well as
complex numbers for all ports.  The stmhal port has ADC working on L4
microcontrollers, fixed initialisation for DAC, and addition of the
machine.WDT class and machine.reset_cause function.

For the ESP8266 port Pin(16) now works as an input pin and the hardware
SPI peripheral is exposed as machine.SPI(1).  The os.umount function is
implemented and the port supports mounting of externally connected SD
cards.  The machine.WDT class is added, wlan.scan() is fixed to return all
access points, and there is support for DS18S20 devices.

py core:
- runtime: factor out exception raising helpers
- runtime: define mp_check_self(pred) helper macro
- objdict: get rid of asserts (remove/replace with mp_check_self())
- get rid of assert() in method argument checking functions
- objtuple: in tuple_cmp_helper, use mp_check_self instead of raising
- objstr: use mp_raise_{Type,Value}Error instead of mp_raise_msg
- obj.h: for obj reprs A,B,C use void* explicitly for mp_obj_t typedef
- mpconfigport.h: remove typedef of machine_ptr_t, it's no longer needed
- sequence: allow to use bignums as indices in slice objects
- stream.c: use mp_obj_get_type in mp_get_stream_raise
- gc: add MICROPY_GC_CONSERVATIVE_CLEAR option to always zero memory
- compile: don't compile assert statements when optimisations enabled
- modstruct: use more compact mp_raise_ValueError function
- emitglue: use more compact mp_raise_ValueError function
- rename struct mp_code_state to mp_code_state_t
- mkrules.mk: allow to override name of libmicropython.a
- mpprint: fail an assertion with unsupported format specifiers
- makeqstrdata.py: compute the qstr hash from bytes, not characters
- if str/bytes hash is 0 then explicitly compute it
- emitglue.c: provide mp_raw_code_load_file for any unix architecture
- add MICROPY_USE_INTERNAL_PRINTF option, defaults to enabled

extmod:
- modwebrepl: set_password(): raise exception for too long password
- uzlib/: update uzlib to v2.0: new API supporting stream decompression
- moduzlib: refactor to new stream-compatible uzlib 2.0 API
- uzlib/: update uzlib to v2.0.1: fixes for pedantic compiler warnings
- uzlib/: update uzlib to v2.0.2: consistently use stdint types
- modbtree: do CHECK_ERROR after __bt_seq()
- modubinascii: implement binascii.crc32
- modubinascii: make crc32() support configurable
- modframebuf: fix pixel accessor to return a 1-bit result
- add machine_spi with generic SPI C-protocol and helper methods
- modframebuf: fix fill and scroll when height not divisible by 8
- moduzlib: implement zlib stream decompressor class, DecompIO
- moduzlib: use mperrno.h for error constants
- modframebuf: include font from stmhal directory explicitly
- moduzlib: support wbits arg to DecompIO
- framebuf: add the xstep!=0 case to scroll() method

lib:
- utils/stdout_helpers: fix function signature to match py/mphal.h
- berkeley-db-1.xx: update to upstream, fixes MacOSX build
- utils/pyexec: qstr_pool_info() requires size_t* parameters

drivers:
- sdcard: port the SDCard driver to new machine API, with backwards
  compatibility for pyboard

tools:
- mpy-tool.py: support freezing float literals with obj-repr C
- mpy-tool.py: store qstr config values in global config object
- mpy-tool.py: compute the hash value for str/bytes objects
- mpy-tool.py: support freezing of complex numbers

tests:
- rename zlibd_decompress.py -> uzlib_decompress.py
- basics: add more tuple tests to improve coverage testing
- basics: add more list tests to improve coverage testing
- misc/non_compliant: add tests to improve coverage testing
- basics: add test for break from within try within a for-loop
- basics: add a test file for overriding special methods
- basics/special_methods: enable tests for extra special methods
- uzlib_decompress: actually test raw DEFLATE stream
- run-tests: disable thread/thread_lock4.py on Travis
- run-tests: disable thread/stress_heap.py when running on Travis
- cmdline: add test for -O option to check optimisation value
- extmod/vfs_fat_ramdisk: add tests for VFS.umount()
- run-tests: disable thread_gc1.py test on Travis
- unix/extra_coverage: add test for str/bytes with invalid hash
- extmod: add test for uzlib.DecompIO
- extmod: add a test for framebuf module, tested by coverage build
- extmod/uzlib_decompio: add zlib bitstream testcases
- extmod/framebuf1: add tests for scrolling in the x-direction
- run-tests: disable thread/stress_recurse.py test on Travis

unix port:
- mpconfigport.h: don't include stdio.h on MacOS
- when find'ing frozen files don't use extra slash, do follow symlinks

qemu-arm port:
- enable MICROPY_PY_ALL_SPECIAL_METHODS

stmhal port:
- boards: update STM32L476 pin defs to include ADC channels
- adc.c: get ADC working on STM32L4 MCUs
- fix timer capture/compare interrupt handling for TIM1 and TIM8
- remove obsolete code for special handling of TIM3 irq settings
- make ADC channel 16 available on L4 MCUs
- update pin print to print new constants
- modusocket: set self->nic to MP_OBJ_NULL after socket close
- update boot.py files to use VCP instead of CDC
- spi: factor out SPI transfer code to a single function
- spi: support new machine SPI methods in legacy SPI object
- add machine.WDT class
- set STM32F7DISC CPU Frequency to 216 MHz
- dac: fix DAC (re-)initialisation by resetting DMA
- wdt: implement keyword args to WDT constructor
- modmachine: implement machine.reset_cause() function, and consts
- machine.POWER_ON is renamed to machine.PWRON_RESET
- when find'ing frozen files don't use extra slash, do follow symlinks

cc3200 port:
- add machine.PWRON_RESET constant (machine.POWER_ON is now deprecated)

teensy port:
- fix execution of frozen boot.py and main.py

esp8266 port:
- fix reading of pin object for GPIO16; Pin(16) now works as an input
- PULL_UP is not supported on Pin(16), so raise an exception in this case
- enable support for all special methods
- modpybhspi: add a HSPI module for hardware SPI support
- modmachinespi: add a factory method for SoftSPI/HSPI
- esp_mphal: no longer disable watchdog on startup
- modpybrtc: use 64-bit arithmetic when computing alarm expiry
- hspi: enable duplex operation of hardware SPI
- modous: add os.umount method to unmount a filesystem
- modmachinewdt: implement machine.WDT class
- modules: split onewire.py into OneWire and DS18X20 driver
- modules/onewire: change onewire.read() to onewire.readinto()
- modules/ds18x20.py: add support for DS18S20 devices
- modpybspi: use generic SPI helper methods to implement SPI
- modpybhspi: simplify HSPI driver by using 1 function for xfers
- modmachinewdt: add .deinit() method
- modmachine: add WDT_RESET and SOFT_RESET constants
- modmachine: don't expose internal SoftSPI and HSPI classes
- modmachine: simplify SPI class implementation multiplexing
- espneopixel: disable IRQs during eps.neopixel_write
- modnetwork: fix wlan.scan() method so it returns all networks
- modmachine: map PWR_ON_RESET to vendor's REASON_DEFAULT_RST
- machine.PWR_ON_RESET is renamed to machine.PWRON_RESET
- when find'ing frozen files don't use extra slash, do follow symlinks

docs:
- esp8266/tutorial/pins: fix typo in commands for pin input mode
- esp8266/intro: add command to install esptool.py 1.0.1 via pip
- library/machine.WDT: add note that WDT is only available on WiPy
- esp8266/quickref: fix and update the SPI docs
- esp8266: update quickref and tutorial for OneWire/DS18X20 driver
- pyboard: update USB mouse tutorial to use VCP instead of CDC
- pyboard: update USB mouse tutorial to use pyb.USB_HID()
- library: add reference for pyb.usb_mode and pyb.USB_HID
- pyboard/quickref: add links to pinouts for other pyboard variants
- pyboard/quickref: add section on "delay and timing" for utime mod
- esp8266/quickref: add internal links to docs for some modules
- esp8266/quickref: update information on SPI classes
- esp8266/quickref: further improvements for SPI subsections
- library/machine.WDT: add that WDT is available on pyboard
- reference/isr_rules.rst: two minor additions to docs for using ISR

misc:
- add *.pyc to .gitignore, because Python 2 doesn't use __pycache__
- build mpy-cross as part of the Travis process

Many small improvements and additions, with btree support in ESP8266 …

…port

This release brings various improvements and additions to the core,
extended modules and the ESP8266 port, as well as enhancements to the docs.
There is now a "threshold" function in the gc module for the user to
configure the garbage collector to run earlier than usual, in order to help
reduce fragmentation of the heap.  The btree module is now available in the
ESP8266 port, and there is improved WebREPL file transfer: get file is now
non-blocking (this change requires an update of the client software).

py core:
- nlrx64.S: prefix mp_thread_get_state with an underscore on Mac
- stream: implement 2- and 3-arg write() method as an extension to CPython
- gc: implement GC running by allocation threshold, user configurable
- fix nlrthumb.c when DEBUG=1 is defined
- obj: issue a warning when str and bytes objects are compared
- mpconfig.h: fix description for MICROPY_PY_STR_BYTES_CMP_WARN
- objstrunicode: str_index_to_ptr: should handle bytes too
- objstrunicode: str_index_to_ptr: implement positive indexing properly
- stream: implement generic flush() method, in terms of C-level ioctl
- objstringio: add MP_STREAM_FLUSH ioctl and flush() method
- objstringio: implement MP_STREAM_SEEK ioctl and add seek() method
- stream: add adapter methods with POSIX-compatible signatures
- mpconfig.h: add MICROPY_STREAMS_POSIX_API setting
- py.mk: extra switches to build "embedded" BerkeleyDB BTree lib
- mkrules.mk: allow to add more items for "clean" target using CLEAN_EXTRA
- objstr: make .partition()/.rpartition() methods configurable
- mpconfig.h: define MP_ALWAYSINLINE for reuse

extmod:
- modussl: rename to modussl_axtls.c, to allow impl using other SSL libs
- modussl_axtls: further changes to allow alternative SSL modules
- modussl_axtls: add dummy setblocking() method
- vfs_fat: implement rmdir() method (aliases to unlink)
- modussl_axtls: use mp_stream_close() method
- modwebrepl: use mp_stream_close() method
- modbtree: check __bt_open() return value for error
- modbtree: switch to accepting stream object instead of filename
- modbtree: implement __contains__ operation
- modwebrepl: factor out "GET" iteration to write_file_chunk()
- modwebrepl: make GET_FILE operation non-blocking
- modbtree: open(): add option kwargs
- modwebsocket: add readline method
- modwebsocket: make compatible with non-default object models
- modwebsocket: use mp_rom_map_elem_t and friends
- modwebrepl: add GET_VER operation to query MicroPython version

lib:
- axtls: upgrade to axTLS 1.5.4 + MicroPython patchset
- axtls: update, fixes esp8266 build
- utils/stdout_helpers: move from minimal/uart_extra.c for reuse
- embed/abort_: implementation of abort_() function raising uPy exception
- berkeley-db-1.xx: switch to "embedded" branch
- berkeley-db-1.xx: update, sets default page size to 4096

tests:
- add test for extended arguments to stream .write() method
- extmod/machine_pinbase: skip if machine.PinBase is not available
- bytes_compare: rework test for bytes <-> str comparison
- extmod/btree1: close database at the end of test
- unicode_subscr.py: detailed test for subscripting unicode strings
- run-tests: make "regex'ed .exp" facility available to device tests
- io/bytesio_ext: test for .seek()/.flush() on BytesIO
- extmod/btree1: tests against in-memory DB (using io.BytesIO)
- machine_mem.py: too non-portable, rework as an example for unix port
- machine1: revamp to work with unix port (which has "umachine")
- basics: bytes/str.partition/rpartition are now optional

mpy-cross:
- fix Makefile to handle gc-sections linker flags on OS X
- use binary file translation mode for creating mpy files on windows
- fix mingw and msys2 compilation

minimal port:
- disable MICROPY_GC_ALLOC_THRESHOLD

unix port:
- mpthreadport: adjust minimum thread stack, and stack limit check
- cache libaxtls.a in local build dir
- disable MICROPY_GC_ALLOC_THRESHOLD for minimal build
- enable MICROPY_PY_STR_BYTES_CMP_WARN
- mpconfigport.h: include stdio.h by default
- file: implement MP_STREAM_FLUSH ioctl
- file: ioctl(): check that file is open before operations
- file: fdfile_ioctl(): fix argument to check_fd_is_open()
- file: use generic stream flush() method
- enable websocket module
- moduselect: allow poll.register(), etc. accept fd-like objects

stmhal port:
- fix malloc when used with external libraries
- make SPI NSS pin definition optional
- fix I2C mappings for STM32F429DISC board

esp8266 port:
- select axTLS for SSL implementation, following recent refactor
- moduos: add rmdir() function
- cache Xtensa-built libaxtls.a in local build dir
- enable MICROPY_PY_STR_BYTES_CMP_WARN
- dupterm_task_init() should be called before running _boot.py, etc
- _boot.py: set GC alloc threshold to half of heap size
- _boot.py: decrease GC alloc threshold to quarter of heap size
- modpybuart: fix UART parity setting
- axtls_helpers: remove abort_(), now in lib/embed/
- mpconfigport.h: include sys/types.h for POSIX types definitions
- esp_mphal: implement libc's errno
- enable btree module
- eagle.rom.addr.v6.ld: add Enable_QMode symbol from SDK 2.0.0
- make APA102 driver inclusion configurable
- makeimg.py: store firmware size as last 4 bytes of padding area
- makeimg.py: append md5 hash to the generated binary
- modesp: add check_fw() function to check integrity of the firmware
- scripts/port_diag.py: include esp.check_fw() call
- flashbdev: reserve extra sysparam sector for SDK 2.0.0 compatibility
- scripts/inisetup: add commented-out call to esp.osdebug(None)
- modmachine: implement idle() function
- esp_mphal.h: add mp_hal_ticks_cpu() for reuse
- modutime: actually implement ticks_cpu()
- modmachine: implement dummy sleep() function
- tutorial/intro: reword para abou -fm dio switch
- modules/flashbdev: start filesystem at 0x90000
- esp8266.ld: increase firmware image size to 0x90000 (576K)

docs:
- add DHT to ESP8266 Quick Ref and Tutorial
- fix some spelling mistakes
- array: document array module
- library/index: include array module in ToC
- esp8266/intro: rename to "Getting started" from "Introduction"
- esp8266/intro: add troubleshooting section
- esp8266/quickref: link to installation instructions
- esp8266/tutorial/intro: add anchor for link from quickeref
- esp8266/intro: focus on hazards of unearthed power wrt electronics
- uio: mention seek()/flush() support for io.BytesIO

misc:
- logo/1bit-logo A black & white version of the logo

examples:
- http_server*: update for buffered-like streams (read line by line)
- embedding: example for embedding MicroPython in an app
- embedding: add README
- http_client*: be sure to close socket
- network: split recv- and read-based HTTP servers

qemu-arm:
- enable gcc LTO option for nlrthumb.c

Thread support, ESP8266 memory improvements, btree module, improved docs

This release brings multi-threading support in the form of the _thread
module, which closely matches the semantics of the corresponding CPython
module.  There is support for GIL and non-GIL builds; without the GIL
enabled one must protect concurrent access to mutable Python state at the
Python level using Lock objects.  Threading with the GIL is enabled in
the cc3200 port on the WiPy.  Threading without the GIL is enabled on the
unix port.  The ESP8266 port has support for frozen bytecode (for scripts
in the modules/ subdirectory), as well as optimisations for reduced
memory usage and decreased memory fragmentation.  The ESP8266 RTC also
resumes correctly after a deepsleep.  An initial "btree" module has been
implemented for database support (unix port only), and the documentation
has been further improved, with pre-built PDF versions of the docs now
available.

py core:
- parse: treat constants that start with underscore as private
- objdict: implemented OrderedDict equality check
- support to build berkeley db 1.85 and "btree" module
- mpconfig.h: MP_NOINLINE is universally useful, move from unix port
- makeqstrdefs.py: remove restriction that source path can't be absolute
- mkrules.mk: define "lib" outside conditional block
- rename __QSTR_EXTRACT flag to NO_QSTR
- objtype: instance: inherit protocol vtable from a base class
- mphal.h: if virtpin API is used, automagically include its header
- objtype: inherit protocol vtable from base class only if it exists
- add MP_STATE_THREAD to hold state specific to a given thread
- add basic _thread module, with ability to start a new thread
- modthread: properly cast concrete exception pointer to an object
- modthread: add stack_size() function
- modthread: add exit() function
- modthread: implement lock object, for creating a mutex
- modthread: add with-context capabilities to lock object
- gc: make memory manager and garbage collector thread safe
- modthread: satisfy unused-args warning
- gc: fix 2 cases of concurrent access to ATB and FTB
- modthread: be more careful with root pointers when creating a thread
- modthread: call mp_thread_start/mp_thread_finish around threads
- gc: fix GC+thread bug where ptr gets lost because it's not computed
- make interning of qstrs thread safe
- implement a simple global interpreter lock (GIL)
- don't use gc or qstr mutex when the GIL is enabled, there is no need
- modthread: make Lock objects work when GIL is enabled
- mpthread.h: move GIL macros outside MICROPY_PY_THREAD block
- modthread: allow to properly set the stack limit of a thread
- nlrthumb: convert NLR thumb funcs from asm to C with inline-asm
- nlrsetjmp: update to take into account new location of nlr_top
- mpthread: include mpstate.h when defining GIL macros
- gc: be sure to count last allocated block at heap end in stats
- gc: calculate (and report) maximum contiguous free block size
- builtinimport: disable "imported as namespace package" warning
- mpconfig.h: mention MICROPY_PY_BTREE config option
- objarray: split out header to allow direct access to object
- rename mp_obj_type_t::stream_p to "protocol"

extmod:
- modbtree: initial implementation of "btree" module based on BerkeleyDB
- modbtree: handle default value and error check
- modbtree: implement .items() iterator
- modbtree: actually implement end key support for .items()
- modbtree: items(): Implement "end key inclusive" flag
- modbtree: items(): Implement DESC flag
- modbtree: __getitem__() should raise KeyError for non-existing key
- modbtree: open(): Support "in-memory" database with filename=None
- machine_pinbase: implementation of PinBase class
- machine_pinbase: fix nanbox build
- modlwip: store a chain of incoming pbufs, instead of only one
- modbtree: implement keys(), values(), items() iterators
- modbtree: cleverly implement "for key in btree:" syntax
- modwebsocket: add readinto() method
- modwebrepl: add readinto() method
- modbtree: fix unused argument warning
- modbtree: fixes for nanbox build
- moduos_dupterm: reserve buffer bytearray object for dupterm
- moduos_dupterm: reuse dupterm_arr_obj for write operations

lib:
- berkeley-db-1.xx: add Berkeley DB 1.85 as a submodule
- berkeley-db-1.xx: update to upstream which builds for uPy
- fatfs/option/ccsbcs: follow uPy optional features model
- libm: format code to pass gcc v6.1.1 warning
- libm: remove unused definition of "one"

drivers:
- display/ssd1306: add width arg and support 64px wide displays

tests:
- recursive_iternext: clang/Linux is even more stack-frugal than MacOS
- bench: add testcase to compare bytes(N) vs b"\0" * N
- add testcase for OrderedDict equality
- add a testcase for machine.PinBase class
- extmod: add "btree" module test
- btree1: add testcase for iterating btree object directly
- add tests for _thread module
- add 3 more tests for _thread module
- thread: remove need to sleep to wait for completion in some tests
- thread: add tests for running GC within a thread, and heap stress
- thread: rename thread_stress_XXX.py to stress_XXX.py
- thread: add tests that mutate shared objects
- thread: add test for concurrent interning of strings
- thread: add test for concurrent mutating of user instance
- thread: make stack-size test run correctly and reliable on uPy
- thread: make sure that thread tests don't rely on floating point
- thread: allow thread_sleep1 to run without floating point
- thread: allow some tests to run on ports with not much heap
- meminfo: update for addition of "max free sz" output
- run-tests: If running thread tests on unix, don't run mutate ones

unix port:
- unbreak "minimal" target by disabling FatFs
- mpconfigport_minimal.h: clearly mark where user-define config ends
- deprecate support for GNU Readline (MICROPY_USE_READLINE=2)
- time to build with --gc-sections
- move "utime" module config to C level instead of make level
- Makefile: libffi: Build with -Os
- alloc: add option to use uPy's alloc-exec implementation even for libffi
- alloc: make coverage build and its overzealous warnings happy
- disable FatFs VFS for normal build, keep enabled for coverage
- modmachine: include PinBase class
- modmachine: enable time_pulse_us() function
- fix Makefile to handle gc-sections linker flags on Mac OS
- add basic thread support using pthreads
- file: if write syscall returns because of EINTR then try again
- implement garbage collection with threading
- mpthreadport: use SA_SIGINFO for GC signal handler
- gccollect: provide declaration of exported function
- mpthreadport: suppress compiler warning about unused arguments
- modtime: release the GIL when sleeping
- enable btree module
- Makefile: make "minimal" build be minimal again
- mpconfigport_minimal.h: allow to print a string within 1KB of heap
- main: error out on unknown value of suffix in -X heapsize= option
- main: improve help for -X options a bit
- main: when preparing sys.path, allocate exact strings on uPy heap
- disable the GIL to improve performance of non-thread code

windows port:
- follow unix port changes regarding "utime" module
- msvc: include machine_pinbase.c in build and enable umachine module

stmhal port:
- add board definition files for Olimex STM32-E407
- port of f4 hal commit 1d7fb82 to l4 hal (SD card modifications)
- correct DMA to allow SD card on L4 MCUs
- enable SD card on L4 MCUs

cc3200 port:
- update FreeRTOS to v9.0.0
- define our own FreeRTOS heap so it can go in a special segment
- add basic threading capabilities
- fix call to new exception to be _msg instead of _arg1
- use xTaskCreateStatic instead of osi_TaskCreate
- mpthreadport: make mutex statically allocated
- mpthreadport: properly initialise the main thread's data
- gccollect: use MP_STATE_THREAD(stack_top) to get top of stack
- mpthreadport: scan more root pointers from thread data
- mpthreadport: move mem alloc outside the thread_mutex lock
- enable the GIL
- in FreeRTOSConfig.h, comment on configSUPPORT_STATIC_ALLOCATION
- remove .boot section attribute from osi_TaskCreate function
- start the simplelink spawn task using the static task creator
- shrink the FreeRTOS heap and place TCB+stack in freed location
- allow to compile bootloader with threading enabled
- remove obsolete singleton heart-beat object

teensy port:
- update the README with OSX specific information and tips

esp8266 port:
- modnetwork: use struct bss_info::ssid_len for ESSID length
- let RTC work correctly after deepsleep
- switch floating-point arith routines to BootROM
- Makefile: enable --verify option for esptool.py write_flash
- use RTC to set date & time stamps for files
- main.c: clear the command line history when (re)booting
- enable frozen bytecode, with scripts in modules/ subdir
- README: describe how to build mpy-cross
- websocket_helper.py: avoid extra string allocations
- websocket_helper.py: fix typo in debug output
- modpybuart: allow setting baudrate and other params
- explicitly collect garbage in bootstrap scripts
- switch webrepl_setup to use frozen bytecode
- switch webrepl to use frozen bytecode
- README: promote from "highly experimental" to "experimental"
- main: init recently added dupterm_arr_obj port state var
- esp_mphal: call_dupterm_read: Use readinto() method
- esp_mphal: properly handle dupterm EOF after switching to readinto()

qemu-arm port:
- disable gcc LTO option for nlrthumb.c

docs:
- esp8266/tutorial/network_basics: minor typo fix, ap becomes ap_if
- add link to PDF version of docs in sidebar
- library/network: wipy: fix literal block indentation
- esp.socket: remove unused file
- ure: typo fix
- usocket: there must be empty line after .only::
- library/machine.Pin: mention GPIO and cross-link .value() function
- machine.*: add "currentmodule:: machine" directive
- pyb.*: add "currentmodule:: pyb" directive
- machine.Pin: remove explicit target
- machine.UART: cleanup pyboard section
- machine.*: use proper class case in method headers
- machine.Pin: add class designator to all constants
- pyb.CAN: mark CAN.initfilterbanks() as classmethod explicitly
- pyb.Pin: af_list() is a normal method, not a class method
- pyb.ExtInt,pyb.Pin: mark up class methods as such
- pyb.*: use proper class case in method headers
- pyb.Pin: sort .af() and .af_list() methods together
- builtins: enumerate all builtin functions implemented
- library/index: add builtins.rst
- machine.Pin: disambiguate object call method
- machine*: remove explicit targets and "machine." prefixes on classes
- uctypes: improve documentation
- sys: detailed description of print_exception() diff from traceback module
- add sphinx_selective_exclude extension suite
- conf.py: active sphinx_selective_exclude extensions
- rebuild docs from scratch, as required for proper only:: handling
- select: add an article
- sys: print_exception: Fixes/clarifications
- conf.py: exclude cmath from modindex for wipy
- library: fix typo in docs for usocket.listen()

examples:
- unix/ffi_example.py: update for current "ffi" module API
- unix/ffi_example.py: remove TODO, make output more clear

Many ESP8266 improvements, enhanced WebREPL, and support for STM32L4 …

…MCUs

This release brings general improvements and bug fixes, and some new
features.  There is now a uerror module for consistent errno handling
across ports, as well as textual names of OS errors that are printed when
an OSError is raised.  There is support for frozen packages, via both
frozen scripts and frozen bytecode.  WebREPL on the ESP8266 is greatly
improved with many bug fixes and now supports an unlimited (or very large)
number of reconnects.  The os module on the ESP8266 now has rename, chdir,
getcwd and stat.  The unix port now includes the ussl module by default.
The stmhal port has support for STM32L4 MCUs including the STM32L476
Discovery board and the LimiFrog board.

README:
- add explicit note that subdirs contain more READMEs
- add "make deplibs" to quick build section
- "quick build": Use "make axtls" after all

CODECONVENTIONS.md:
- describe git commit messages conventions

py core:
- obj: add warning note about get_array return value and GC blocks
- objstr: binary type of str/bytes for buffer protocol is 'B'
- runtime: properly handle passing user mappings to ** keyword args
- repl: if there're no better alternatives, try to complete "import"
- mpz: fix bug with overflowing C-shift in division routine
- mpz: do Python style division/modulo within bignum divmod routine
- mpz: fix mpn_div so that it doesn't modify memory of denominator
- vstr: vstr_null_terminated_str(): Extend string by at most one byte
- vstr: change allocation policy, +16 to requested size, instead of *2
- add mperrno.h file with uPy defined errno constants
- add uerrno module, with errno constants and dict
- parse: add uerrno to list of modules to look for constants in
- mperrno: add EAFNOSUPPORT definition
- repl: fix handling of backslash in quotes when checking continuation
- gc: gc_dump_alloc_table(): Show byte/str and (byte)array objects
- gc: make (byte)array type dumping conditional on these types being enabled
- gc: use '=' char for tail blocks when dumping heap
- mperrno: add some more MP_Exxx constants, related to networking
- moduerrno: add more constants to the errno module
- add mp_errno_to_str() and use it to provide nicer OSError msgs
- objfloat, py/modmath: ensure M_PI and M_E defined
- emitglue: fix build on AArch64 (ARMv8, etc.) related to loading .mpy files
- objexcept: don't convert errno to str in constructor, do it in print
- moduerrno: add EACCES, pretty common error on Unix
- gc: gc_dump_alloc_table(): dump heap offset instead of actual address
- objstr: make dedicated splitlines function, supporting diff newlines
- objstringio: add TODO comment about avoiding copying on .getvalue()
- modstruct: raise ValueError on unsupported format char
- stream: support both "exact size" and "one underlying call" operations
- declare constant data as properly constant
- stream: add mp_stream_close() helper function
- mphal.h: provide default prototypes for mp_hal_delay_us/mp_hal_ticks_us
- rework frozen modules support to support packages
- objstr: implement str.center()
- allow to stat and import frozen mpy files using new frozen "VFS"
- makeqstrdata.py: allow to have double-quote characters in qstrs
- objnamedtuple: allow passing field names as a tuple
- moduerrno: add EEXIST, EISDIR, ECONNREFUSED
- modstruct: allow to have "0s" in struct format

extmod:
- modlwip: convert errno's to use MP_Exxx symbols
- modlwip: rework how Python accept callback is called
- when including extmod headers, prefix path with extmod/
- modwebsocket: add close() method
- modwebrepl: add close() method
- moduos_dupterm: dumpterm subsystem is responsible for closing stream
- modussl: make more compatible with non-default obj representations
- machine_i2c: redo mp_hal_pin macros to use open_drain and od_low
- virtpin: initial implementation of open-ended C-level Pin interface
- vfs_fat: replace text error messages by POSIX error numbers
- vfs_fat: add chdir() method
- vfs_fat: add getcwd() method
- vfs_fat: add vfs.stat() method
- add machine time_pulse_us function (at C and Python level)
- machine: add MICROPY_PY_MACHINE_PULSE config for time_pulse_us

lib:
- timeutils/timeutils: timeutils_mktime may accept negative time values

drivers:
- cc3000: rename timeval to cc3000_timeval, to avoid clash
- add C-level function to read DHT11 and DHT22 devices
- display/ssd1306: update SSD1306_SPI to work with new API

tools:
- make-frozen.py: properly escape hex chars when making C strings
- make-frozen.py: quick fix to support package-modules
- mpy-tool.py: add checks for critical configuration vars
- make-frozen.py: update for latest changes in frozen modules support
- mpy-tool.py: include .py extension in frozen filename
- mpy-tool.py: don't strip directories from the frozen source name
- upgrade upip to 0.7: SSL cert warning, use uerrno, better usage message

tests:
- run-tests: factor out list of supported external boards
- disable memoryview tests that overflow int conversion
- basics/string_splitlines: reinstate feature test for splitlines
- struct1: add testcase for an unknown type char
- add testcase for str.center()
- extmod/vfs_fat_ramdisk: add testcases for chdir(), getcwd()
- misc/recursive_iternext.py: increase depth N from 1000 to 2000
- misc/recursive_iternext.py: provide more fine-grained selection of N
- pyb/rtc: make RTC test on pyboard more reliable by calling init()

mpy-cross:
- add -s option to specify the embedded source filename

unix port:
- mphalport: add mp_hal_delay_us() for consistency with other ports
- enable uerrno module
- add ability to include frozen bytecode in the build
- mpconfigport_coverage.h: add dedicated config file for coverage build
- unix_mphal: implement mp_hal_ticks_us()
- support frozen packages
- Makefile: nanbox build is not compatible with modussl, disable
- enable "ussl" module
- mpconfigport.mk: document MICROPY_STANDALONE make-level option
- Makefile: "make axtls": automatically fetch submodules if missing

windows port:
- enable multi-processor compilation for msvc

stmhal port:
- l4: adapt DMA to be able to support STM32L4 MCU series
- l4: adapt startup code, clock configuration and interrupts
- l4: make CCM/DTCM RAM start-up conditional on MCU type
- l4: add support for machine.sleep on STM32L4 MCUs
- dma: make DAC DMA descriptors conditional on having a DAC
- add board files for LIMIFROG board
- for LIMIFROG board, add early-init function to get to DFU mode
- dma: fix builds for boards with an F4 or F7 but no DAC
- sdcard: fix initialisation of DMA TX so that writes work
- can: allow to get existing CAN obj if constructed without args
- fix clock configuration for STM32L476-discovery; also add I2C2
- convert to use internal errno symbols; enable uerrno module
- for network drivers, convert to use MP_Exxx errno symbols
- led: allow LEDs to be in PWM mode with TIM1 and channels 1-4
- i2c: expose I2CHandle3 for use by custom C code
- sdcard: allow to do unaligned read-from/write-to SD card
- support frozen packages using .mpy files
- moduos: getcwd(): use mp_obj_new_exception_arg1()
- dac: add DAC deinit() method
- uart: fix wrong baudrate calculation for stm32l4 series

esp8266 port:
- scripts/: remove use of pin.PULL_NONE
- scripts/inisetup: don't start WebREPL on boot in master branch
- scripts/: add fill() to NeoPixel
- scripts/webrepl: add optional password argument to webrepl.start()
- scripts/webrepl: add start_foreground() method
- main: bump heap size to 28K
- mpconfigport: reduce various parser-related allocation params
- help: add "sta_if.active(True)" command
- convert to use new MP_Exxx errno symbols
- enable uerrno module, weak linked also as errno
- change to use internal errno's
- moduos.c: addition of the rename method to module uos
- scripts/port_diag: add network diagnostic output
- scripts/webrepl_setup: show password placeholder char
- scripts/webrepl_setup: add max password length check
- README: add a very first start section
- add APA102 serial individually controllable LEDs support
- enable collections.OrderedDict
- main: update _boot module loading for recent frozen modules refactors
- scripts/port_diag: dump network interface IP settings
- esp_mphal: fix NLR buffer leak in call_dupterm_read()
- esp_mphal: handle Ctrl+C from dupterm (e.g. WebREPL)
- esp_mphal: mp_uos_dupterm_deactivate() may raise exception
- add mp_hal_pin_input() and mp_hal_pin_output() functions
- modpybspi: configure pins when initialising an SPI object
- xtirq: add xtirq.h for controlling xtensa irqs
- ets_alt_task: don't run ets_loop_iter if irqs are disabled
- modmachine: add disable_irq and enable_irq functions
- enable DHT C-level driver
- add dht.py script for high-level control of DHT11/DHT22 sensor
- Makefile: document "disable" value for UART_OS
- modnetwork: scan() is only supported by STA when it's enabled
- modnetwork: protect scan() callback against memory errors
- modnetwork: allow to press ctrl-C while scan() is running
- uart: properly initialise UART0 RXD pin in uart_config
- moduos: add chdir() and getcwd() functions
- scripts/ntptime: allow to override NTP server
- modmachine: add machine.time_pulse_us function
- enable MICROPY_PY_IO_FILEIO to get compliant text/binary streams
- moduos.c: add stat() to the module uos of esp8266
- rtc: set RTC user memory length to 0 on first boot
- provide a dedicated variable to disable ets_loop_iter
- modpybrtc: handle RTC overflow

docs:
- machine.UART: filter out unimplemented UART methods from esp8266 docs
- esp8266/quickref: new way to get MAC address
- esp8266/quickstart: remove i2c examples with stop=False
- ustruct: describe supported type codes
- ussl: add basic description of axTLS-based modussl
- esp8266: Include ussl module in the docs
- machine: make disable_irq and enable_irq docs available for all
- library/machine: add documentation for machine.time_pulse_us
- math, cmath: add port availability information
- library/index: add intro paragraph regarding availability of modules
- README: add some hints for PDF docs generation
- wipy/tutorial: add note about screen key bindings on OS X
- esp8266/quickref: update WebREPL section for 1.8.1 release
- esp8266: fix ESP8266 Network tutorial
- esp8266/quickref: use local image of Adafruit Huzzah board
- esp8266/general: add note about RTC overflow

travis:
- install gcc-arm-none-eabi with --force-yes for now

First general release of ESP8266 port, and support for frozen bytecode

This release marks the first general release of official ESP8266 support
within the MicroPython code base.  The ESP8266 port has many improvements
and additions, including: websocket and webrepl modules, deep-sleep mode,
reading on UART, enhanced I2C support, enhanced network configuration,
full sequence of start-up scripts (built-in _boot.py, boot.py and
main.py), improved filesystem support with automatic flash-size detection
as well as documentation and a tutorial.

Known issues with ESP8266 port are:
- Basic SSL support is available but it works only with relatively short
  data lengths (a few kilobytes).
- WebREPL over SSL is not supported.
- Only 5 or so WebREPL sessions in succession can be started (including
  file transfer sessions), after that the board requires a hard reset.
- File transfer over WebREPL has issues with large files (above a few
  tens of kilobytes).
- By design, only one concurrent WebREPL connection is supported.
- Soft reset doesn't reset the network stack.

In addition to ESP8266 support, this release brings frozen bytecode
which allows to compile bytecode offline and link it into the firmware,
completely eliminating the need for compilation (and the associated
RAM usage) at runtime.  Basic async/await syntax is now supported, and
qstrs are now auto-generated in the build system.

A detailed list of changes is given below.

README:
- explicitly point to required dependencies section
- promote "docs" and "tests" to "major components"
- mention support "async" keyword from Python 3.5

ACKNOWLEDGEMENTS:
- add list of 842 backers from the ESP8266 campaign

py core:
- modbuiltins: add comment about setting "_" special var
- add async/await/async for/async with syntax
- fix constant folding and inline-asm to work with new async grammar
- emitglue: move typedef of mp_raw_code_t from .c to .h file
- emitglue: make mp_raw_code_t* arguments constant pointers
- makeqstrdata: factor out some code to functions that can be reused
- add ability to have frozen persistent bytecode from .mpy files
- makeqstrdata: add more names for escaped chars and esc non-printable
- simplify "and" action within parser by making ident-rules explicit
- makeqstrdata: fix rendering of qstrs that have non-printable ASCII
- makeqstrdata: add special case to handle \n qstr
- declare help, input, open builtins in core
- map: change hash-table allocation policy to be less aggressive
- makeqstrdefs: add script to automate extraction of qstr from sources
- frozenmod: pass the source name of the frozen module to the lexer
- rework QSTR extraction to work in simple and obvious way
- divide "split" and "cat" phases of qstr extraction for better efficiency
- fix bug passing a string as a keyword arg in a dict
- move call_function_*_protected() functions to py/ for reuse
- makeqstrdefs.py: windows compatibility
- obj.h: when constructing a small-int cast to mp_uint_t for bit-shift
- emitnative: use MP_OBJ_NEW_SMALL_INT instead of manual bit shifting
- vm: "yield from" didn't handle MP_OBJ_STOP_ITERATION optimization
- modio: rename module name to "uio" for consistency with other modules
- modcollections: rename module name have "u" prefix for consistency

extmod:
- add initial framebuf module
- add generic machine.I2C class, with bit-bang I2C
- machine_i2c: fix I2C reading by sending ack/nack at end of byte
- machine_i2c: implement I2C memory reading/writing
- moduos_dupterm: don't swallow exceptions in dupterm's read()/write()
- modlwip: lwip_tcp_receive(): Properly handle EOF for non-blocking sock
- modlwip: more debug messages for various edge conditions
- fsusermount: in mount/mkfs, deregister VFS object on error
- modlwip: lwip_tcp_send(): full error handling
- modlwip: lwip_tcp_receive(): full error handling
- modlwip: add ability to run callback on "recv" and "accept" events
- machine_i2c: allow mp_hal_pin_obj_t to be any type, not a ptr
- modlwip: protect recv/accept Python callback against exceptions
- modlwip: workaround esp8266 sendto issue where 1 is returned
- modlwip: add print_pcbs() debug function
- modwebsocket: handle CLOSE control frame
- modussl: throw Python exceptions in case of errors
- modussl: support server-side SSL sockets
- modussl: SSL_OK from ssl_read() means "no user data so far"
- modwebrepl: module to handle WebREPL protocol
- modwebrepl: initial implementation of "get file" operation
- modwebrepl: keep reading data when there's something to read
- modwebrepl: GET_FILE: Send length-prefix chunk with one write()
- modwebrepl: add rate-limiting workaround for broken network drivers
- modwebrepl: set debugging by default to off
- modwebrepl: add support for password
- modlwip: implement sendall() method for TCP sockets
- fix typo of macro that detects if float is enabled

lib:
- utils/printf: rework overriding printer of DEBUG_printf()
- utils/pyexec: condition-out GC calls from pyexec
- utils/pyhelp: extract implementation of help(obj) to a library function
- axtls: update to the latest upstream, fix reported MacOSX build issue

drivers:
- add SSD1306 OLED driver, with I2C and SPI interfaces

tools:
- mpy-tool.py: new tool to work with .mpy files; currently it can freeze them
- mpy-tool.py: add support for Python 2.7

tests:
- add 6 tests for async await/for/with
- add .exp files for async tests, so they can run with Python 3.4
- fix dict1.py so it doesn't rely on the order of dict elems
- extmod: move split-on-empty-match tests to a separate test file
- add testcase for yielding from a stopped generator
- run-bench-tests: process tests in alphabetical order
- update for _io/_collections module having been renamed

minimal port:
- add example of frozen persistent bytecode (.mpy file)
- disable async/await syntax

unix port:
- build with MICROPY_PY_UHASHLIB_SHA1 if already building with axTLS
- make sure build dir exists before accessing it for freezing upip
- Makefile: make install more compatible (BSD, etc.)

windows port:
- msvc: implement automatic qstr generation using makeqstrdefs

stmhal port:
- implement basic C-level pin HAL
- use new generic I2C object in machine module
- enable framebuf module
- properly handle RTS/CTS flow control for buf/unbuf transfers
- add Makefile option FROZEN_MPY_DIR to support frozen bytecode
- for frozen bytecode generation, add dependency of qstr file
- l4: add CMSIS files to support STM32L476
- l4: add basic STM32L4xx HAL files
- l4: adapt UART HAL to avoid 64-bit integer division
- update HALCOMMITS due to change to hal
- l4: add board definition files for STM32L476DISC
- l4: add line to Makefile for building L4 series
- l4: modify adc.c to add support for STM32L4 series
- l4: modify uart.c to support L4 MCU
- l4: modify usbd_conf.c to support L4 MCU
- l4: modify rtc.c to support L4 MCU
- l4: modify timer.c to support L4 MCU
- fix machine.unique_id() function to work for all MCUs
- l4: modify mphalport to support L4 MCU
- l4: modify flash.c and storage.c to support L4 MCU
- l4: add support for external interrupts/events
- accel: raise an exception if the accel couldn't be initialised
- use pyhelp_print_obj function
- change i2c.scan() method to scan addresses 0x08-0x77
- fix typo of macro that detects if float is enabled

cc3200 port:
- use pyhelp_print_obj function
- change i2c.scan() method to scan addresses 0x08-0x77
- disable async/await syntax

esp8266 port:
- enable websocket module
- modnetwork: .config(): Check interface whose config is requested
- modnetwork: .config(): Add "authmode" param
- modnetwork: .config(): Add "password" param (W/O)
- add Python modules for initial configuration
- scripts/inisetup.py: set WPA/WPA2 AP mode with a predefined password
- protect modpyb.h header file from multiple inclusions
- implement basic C-level pin HAL
- switch from using custom I2C driver to generic extmod one
- enable framebuf module
- in callback helpers, pop nlr_buf on successful call
- esp_mphal: don't swallow exceptions in dupterm's read()/write()
- esp_mphal: call_dupterm_read(): Fix order of deactivating on EOF
- remove pin_id field from C pin object
- add dummy entries for non-existing pins to simplify pin logic
- add hard IRQ callbacks for pin change on GPIO0-15
- separate 1-wire timing funcs from Python module to save iRAM
- switch integer arith routines to BootROM
- scripts/port_diag.py: module to collect diagnostic info
- enable input() builtin
- scripts/_boot: mount block device on "" instead of "/"
- moduos: add uos.mkdir function
- modmachine: add reset_cause() function
- adapt port to use new auto-qstr generation
- moduos: add dupterm_notify() function
- esp_mphal: protect dupterm_task_handler() from recursive exec
- README.md: update feature list for current state of affairs
- modesp: allow esp.deepsleep to take 2nd arg for RF wake opt
- scripts/flashbdev: use all available space in 1MB FlashROM for FS
- modesp: add flash_size() function
- scripts: don't try to create filesystem on 512KB devices or less
- modnetwork: .config(): Add "channel" param
- scripts/flashbdev: disable debug output/checks
- scripts/_boot: print notice when initial setup is executed
- scripts/flashbdev: correct bootloader flash size to match real size
- modnetwork: .config(): Add "hidden ESSID" param
- implement basic deep-sleep capabilities
- add uart_rx_wait and uart_rx_char functions
- implement UART.read functionality
- uart: remove obsolete UART rx buffering code
- esp_mphal: remove mp_hal_feed_watchdog
- convert mp_hal_pin_obj_t from pin ptr to simple integer
- allow GPIO16 to be used as a pin in the uPy pin HAL
- change software SPI driver to use general pin HAL
- scripts/websocket_helper: module encapsulating handshake sequences
- scripts/websocket_helper: disable debug output
- scripts/webrepl: webREPL based on C-level websocket object
- scripts/webrepl: convert to persistent daemon
- scripts/webrepl: don't start on import
- scripts/webrepl: allow to override port
- scripts/webrepl: print connection address
- scripts/webrepl: print client address for incoming connections
- scripts/flashbdev: use all available Flash for filesystem
- scripts/webrepl: add "ws://" to "daemon started at" message
- Makefile: add target to build axTLS
- esp8266.ld: put axTLS to FlashROM
- Makefile: override abort() when building axtls
- axtls_helpers: helper/wrapper functions for axTLS
- tests/onewire.py: don't run test on import
- Makefile: support linking with axTLS built from source
- Makefile: enable "ussl" module; axTLS should be built first using "make axtls"
- move pyb.info() function to esp module and remove pyb module
- move onewire.py, neopixel.py drivers from tests/ to scripts/
- scripts/onewire.py: simplify and improve 1-wire driver
- scripts/neopixel.py: remove test function from neopixel driver
- set suitable values for axtls's RT_MAX_PLAIN_LENGTH & RT_EXTRA
- README: add recently required step of 'make axtls'
- modnetwork: make WLAN.ifconfig() read/write
- help: implement help() builtin
- help: add cheatsheet for basic WiFi configuration
- enable WebREPL file transfer rate limiting
- enable webrepl module
- scripts: move all of initial setup to inisetup module
- scripts/inisetup: create default boot.py in filesystem
- scripts/webrepl: connection ack prompt is now printed by modwebrepl
- scripts/webrepl: switch to using _webrepl object wrapper
- scripts/webrepl: add "first connection" mode to setup password
- README: mention WebREPL
- Makefile: be sure to pass cross-compiling AR when building axtls
- scripts/webrepl_setup: reject too short passwords
- change platform name from ESP8266 to esp8266
- modnetwork: remove deprecated wifi_mode()
- esp_mphal: add ets_esf_free_bufs(), etc. functions
- modesp: add esf_free_bufs() debugging function
- modesp: add malloc() and free() functions
- scripts/inisetup: enable WebREPL auto-start on boot
- modnetwork: remove .mac() method, move to .config("mac")
- scripts/inisetup: update for nic.mac() method being gone
- scripts/neopixel.py: swap red and green in pixel accessor
- modpybpin: use enum+array instead of struct for parsing args
- modpybpin: use None instead of PULL_NONE for no-pull config
- modpybpin: make pin.irq() methods take keyword args
- tutorial: mention that esptool is available via pip
- scripts/ntptime: add simple NTP client

docs:
- esp: enumerate flash access functions
- machine: start to update for esp8266 port
- speed_python: clarify/generalize "Buffers" subsection
- speed_python: generalize "Floating point" subsection
- speed_python: add many more details on memoryviews
- machine: reset_cause() has been implemented for esp8266
- topindex.html: esp8266: Enable quickref/general on the main page
- esp8266/general: start "General information" for esp8266
- esp8266: add info about using deep-sleep mode to quickref
- esp8266/tutorial: add tutorial placeholder page
- ustruct: there's no complete "struct" module, only "ustruct" subset
- esp8266: include usocket module reference
- library/usocket: add link to CPython's socket module
- usocket: socket-specific exceptions are for WiPy only
- usocket: socket.IPPROTO_SEC is WiPy-specific
- usocket: describe address format once at the beginning
- network: esp8266: scan(): add note that bssid is bytes object
- library: group MicroPython-specific modules under separate heading
- library/index: move WiPy "micro-libraries" under corresponding heading
- library/index: esp8266 has the same set of stdlibs as pyboard/unix
- module "time" is actually "utime"
- library/index: make single section for "micro-ified" modules
- library/index: order sections from the most to least standard modules
- Makefile: default BUILDDIR based on MICROPY_PORT
- library: "os" module is actually "uos"
- fix uos and utime heading underlines to be the correct length
- library/utime: add more time functions for unix and esp8266 ports
- utime: describe time() peculiarities in MicroPython
- utime: describe sleep() peculiarities in MicroPython
- library: consistently use admonitions for CPython differences
- ubinascii: clean up grammar
- network: esp8266: Add wlan.ifconfig() method
- network: esp8266: Describe wlan.config() method
- make the short port names in the port/version sidebar lowercase
- esp8266: update quickref to reflect changes to 1-wire and NeoPixel
- library/utime: elaborate on epochs and calendar time maintenance
- esp8266/quickref: add info about WebREPL
- ustruct: document pack_into(), unpack_from()
- sys: document sys.modules
- ustruct: fix argument formatting
- sys: remove port-specific details from description of stdin/out/err
- sys: clarify description of sys.exit()
- sys: clean up print_exception() description
- sys: describe sys.implementation
- sys: describe sys.maxsize
- sys: describe sys.platform is port-neutral manner
- add _collections module reference
- add _io module reference
- _io and _collections were renamed to have standard "u" prefix
- library/machine.I2C: update to reflect ESP8266 implementation
- esp8266/general: webREPL is described in quickref for now
- esp8266/general: add more points to "Multitude of boards" section
- esp8266/general: fix list formatting
- esp8266/general: add techspec section
- esp8266/general: add "Boot process" section
- esp8266_contents: reference general and tutorial docs
- network: esp8266: MAC address is set via .config() method
- esp8266: add ESP8266 tutorial
- machine: generalize docs from just WiPy to other ports
- machine: move WiPy-specific hardware details to its general reference
- machine: more generic description of sleep's, WiPy details to its genref
- machine: idle() description generalization
- library/machine.Pin: update pin docs to reflect ESP8266 support
- esp8266/tutorial: update pins tutorial to reflect changes in API

examples:
- http_server_ssl.py: add HTTPS server example

New MicroPython cross-compiler, and vastly improved ESP8266 port

This release adds the MicroPython cross-compiler that can generate .mpy
files (pre-compiled bytecode) which can be executed within any
MicroPython runtime/VM.  The ESP8266 port is also vastly improved thanks
to a hugely successful Kickstarter campaign.  This port now has an
alternative event loop implementation to allow proper Berkeley sockets
using lwIP built from source, and a greatly improved network module.
Many extension modules are now enabled (ujson, ubinascii, uctypes,
uhashlib, urandom, uheapq, ure, uzlib) and the machine module includes
Timer, Pin, PWM, ADC, I2C, SPI, and basic UART.  Bignums are supported,
along with 30-bit precision floating point, and normal error messages.
There is FatFS support and uos.dupterm.

Many other improvements and bug fixes have been made to the core and
other ports.  The basic test suite can now run within a 16k heap.  Inline
assembler functions now support 4 arguments.  The Unix port has the -i
option to start the REPL after a script is finished.  The stmhal port now
exposes the flash and SD card as proper objects with the block protocol.
There is support for generic STM32F439 boards, the NUCLEO-F411RE board,
and targets to deploy via ST-LINK and OpenOCD.

py core:
- mpprint: fix sign extension when printf'ing %u, %x and %X
- vm: fix popping of exception block in UNWIND_JUMP opcode
- objstr: for str.format, add nested/computed fields support
- objstr: for str.format, don't allocate on the heap for field name
- extend native type-sig to use 4 bits, so uint is separate to ptr
- mpz: complete implementation of mpz_{and,or,xor} for negative args
- mpz: add commented-out mpz_pow3_inpl function, to compute (x**y)%z
- viper: allow casting of Python integers to viper pointers
- viper: allow uint as index to load/store, and give better error msg
- objarray: implement "in" operator for bytearray
- mpstate.h: fs_user_mount is now standard, reusable uPy functionality
- asmx64: add helper macro for generating REX_[WRXB] bits from a reg64
- asmx64: support all 16 regs in reg to memory move instructions
- emitnative: add check that RHS of viper store is of integral type
- repl: check for an identifier char after the keyword
- vm: add macros to hook into various points in the VM
- parse: use m_renew_maybe to ensure that memory is shrunk in-place
- malloc: provide a proper malloc-based implementation of realloc_ext
- emitinlinethumb: use qstrs instead of char* for names of asm ops
- add MICROPY_DYNAMIC_COMPILER option to config compiler at runtime
- stackctrl: add mp_stack_set_top() to explicitly set stack top value
- emitglue: get persistent bytecode working on Linux ARM platform
- objboundmeth: allocate arg state on stack if heap alloc fails
- use MP_SMALL_INT_POSITIVE_MASK to check if uint fits in a small int
- fix passing of some wide int types to printf varg format list
- objarray: fix array slice assignment when array is reallocated
- formatfloat: fix buffer overflow when formatting tiny numbers
- objfun: allow inline-asm functions to be called with 4 arguments
- frozenmod: allow port to override lexer to use for frozen modules
- parse: don't allocate an extra parse node for power exponent
- parse: when looking up consts, check they exist before checking type
- stream: add mp_stream_writeall() helper function
- stream: fix object vs ptr usecase in mp_stream_writeall()
- modio: initial implementation of io.BufferedWriter class
- modio: implement io.BufferedWriter.flush()
- modio: io.BufferedWriter: describe flushing policy
- formatfloat: fix case of float format where leading digit was "10"
- formatfloat: fix further cases of buffer overflow in formatting
- parsenum: use pow function to apply exponent to decimal number
- ringbuf.h: add reusable ring buffer class
- map: prevent map resize failure from destroying map
- move stream-related declarations from obj.h to stream.h
- combine continuous block of emit steps into with_cleanup emit call
- implement basic with support in native emitter
- objarray: fix array.append so it doesn't extend if append fails
- stream: add bigger inventory of stream ioctl's
- stream: add Python-level ioctl() method

extmod:
- update uzlib to 1.2.2
- fsusermount: introduce separate mkfs() function
- fsusermount: implement separate umount() function
- fsusermount: change block protocol to support ioctl method
- modmachine: truncate integers that are to be stored using mem*
- fsusermount: expose umount as a public function
- fsusermount: support mounting of multiple block devices
- vfs_fat: object-oriented encapsulation of FatFs VFS
- vfs_fat_diskio: reusable FatFs module, move from stmhal/diskio
- vfs_fat_file: reusable FatFs module, move from stmhal/file
- vfs_fat_ffconf: reusable FatFs module, move from stmhal/ffconf
- vfs_fat: move listdir() method from stmhal for reuse
- vfs_fat: add .remove() method
- vfs_fat: add .mkdir() method
- vfs_fat: add fat_vfs_import_stat(), reusable import stat routine
- vfs_fat: add .rename() method
- vfs_fat: add lexer, move from stmhal port for reuse
- vfs_fat_lexer: make conditional on FatFs support enabled
- modlwip: add .print() method
- modlwip: implement dummy setsockopt()
- modlwip: add stream protocol read method
- modlwip: add dummy .makefile() method
- modlwip: add stream .read() and .readline() methods
- modlwip: check for state change during recv busy-wait loop
- modlwip: still process remaining incoming data of a closed socket
- modlwip: add .write() stream method
- modlwip: support non-blocking recv()
- modlwip: factor out "socket connected" check to a function
- modlwip: use MICROPY_EVENT_POLL_HOOK for event polling if defined
- modlwip: rework getaddrinfo() data passing
- modlwip: add socket.setblocking() method
- modlwip: lwip_tcp_receive: Properly map lwIP error to POSIX errno
- uctypes: use mp_binary_get_val helper when extracting value
- uctypes: finish support for FLOAT32 and FLOAT64 types
- modwebsocket: start module for WebSocket helper functions
- modwebsocket: implement read support
- modlwip: add SOL_SOCKET and SO_REUSEADDR constants for setsockopt()
- modlwip: implement setsocketopt(SO_REUSEADDR)
- modlwip: lwip_tcp_send: handle properly send buffer full condition
- modlwip: add lwip->POSIX error map for lwIP 1.4.0
- modlwip: lwip_socket_setsockopt: handle option value properly
- vfs_fat_diskio: actually support sectors != 512 with Python blockdevs
- modwebsocket: properly check number of args to constructor
- modure: re_exec() renamed to ure_exec() due to collison in 4.3BSD
- modwebsocket: make sure to propagate EOF
- modwebsocket: reset mask between packets
- modwebsocket: add option for blocking writes to non-blk sockets
- modwebsocket: record current fragment type (binary/text/etc.)
- modwebsocket: allow to get type of last read data using ioctl()
- modwebsocket: implement MP_STREAM_SET_DATA_OPTS ioctl
- modwebsocket: split websocket-related defines for reuse
- modlwip: fix for loss of data in unaccepted incoming sockets
- modwebsocket: support write size beyond 125 bytes

lib:
- fatfs: add support for sector sizes larger than 512 bytes
- axtls: update to the latest upstream master

drivers:
- sdcard: add support for multi-block read/write; add SD test

tests:
- open_plus: add tests for "r+", "w+" open modes
- pyb: add simple test for stm module on pyboard
- run-tests: add esp8266 target
- bytearray1: add testcases for "in" operator
- vfs_fat_ramdisk: add test for VfsFat
- vfs_fat_ramdisk: switch to ioctl-based blockdev API
- vfs_fat_ramdisk: allow to override sector size
- vfs_fat_ramdisk: skip test if can't allocate ramdisk
- skip uctypes and urandom tests not supported byt the WiPy
- vfs_fat_ramdisk: add .listdir() testcase
- vfs_fat_ramdisk: add testcase for .remove()
- vfs_fat_ramdisk: add testcase for .mkdir()
- vfs_fat_ramdisk: allow to run in native mode (don't use "with")
- vfs_fat_ramdisk: add testcase for .rename()
- reduce large object allocations so tests can run with small heap
- print_exception: use exception which prints the same regardless of config
- recursive_iternext.py: make low-heap friendly
- run-tests: simplify handling of newline in output from tests
- run-tests: add cmd line option "--heapsize"
- split large tests into smaller files, to run with a small heap
- add new subdir "stress/" specifically for stress tests
- add a test for argument passing to inline-asm functions
- add test for io.BufferedWriter
- wipy: add Timer class tests
- float2int_fp30: variant of float2int for 30-bit stuffed float
- string_format_fp30: variant of string_format for 30-bit stuffed float

mpy-cross:
- add new component, a cross compiler for MicroPython bytecode
- give a more sensible error message when file doesn't exist
- remove setting of MICROPY_FORCE_32BIT=1 from Makefile

unix port:
- file: stop assuming that O_RDWR == O_RDONLY | O_WRONLY
- enable VfsFat support
- enabled importing of persistent bytecode (.mpy files)
- modsocket: add comment regarding close() error checking (which is none)
- unix_mphal: hack to make uos.dupterm() actually work
- implement -i option (inspect - start REPL after script is finished)
- file: parse "buffering" argument of open() builtin
- file: "encoding" arg to open() isn't kw-only
- djgpp errno.h have no ENOTSUP, so define it to Linux value
- freedos: strip and size names for binaries

stmhal port:
- diskio: introduce MICROPY_HW_HAS_FLASH setting
- move stmhal-specific FatFs routines/structs to fatfs_port.c
- file: recast as "FatFs file" class, to support other VFS types
- file: for self-contained usecase, don't define global types
- improve NUCLEO-F401RE build, with UART2 as REPL
- expose flash and SD card as proper objects with block protocol
- add mount/umount/mkfs to os module
- add a function for setting the pin alternate function
- NUCLEO 401 - Add a bunch of missing pins and reorder the pins
- CERB40 - Add pins defines for I2C3
- NUCLEO 401 - Add definitions for I2C2 and I2C3
- diskio: add provision for default returns for ioctl INIT/SEC_SIZE
- improvements to the STM32F4DISC UART config settings
- enabled importing of persistent bytecode (.mpy files)
- make SPI use mp_hal_gpio_set_af
- switch from dfu-util to tools/pydfu.py for default deploy method
- add stmhal-specific README.md with extra details for this port
- add makefile target to deploy stmhal build via ST-LINK
- add support for generic STM32F439 board (non DISCO)
- add makefile target and configuration to deploy via OpenOCD
- add board definition files for NUCLEO_F411RE
- rename STM32F401NUCLEO to NUCLEO_F401RE
- NUCELO_F401RE cleanup
- consistently enable USB SOF Irqs for all USB modes (FS and HS)

qemu-arm port:
- reinitialise uPy heap and runtime at start of each test
- enable builtin override feature, and enable more tests

cc3200 port:
- add stmhal/builtin_open.c to build
- fix breakage after VfsFat refactor
- finally fix the Timer class API
- improve robustness of the I2C driver
- simplify the Timer API and correct the documents
- fix "debug" build
- improve robustness of WLAN during sleep modes
- rename 'server' class to 'Server' for consistency
- update WiPy software version to 1.2.0

esp8266 port:
- modesp: implement flash_write(), flash_erase()
- README: add hint about adding toolchain to PATH
- modpybrtc: simplify multiplication by fixed-point value
- switch bignum implementation from long-long to mpz
- enable float support, using 30-bit stuffed floats
- enable math module
- allow Makefile's PORT variable to be overridden
- change "soft reboot" message to work with pyboard.py
- add network.ifconfig()
- enable ujson, ubinascii, and uctypes modules
- esp8266.ld: link in SDK version section
- enable config settings helpful for debugging
- enable uhashlib module
- enable more features in mpconfigport.h
- add mp_hal_delay_us function
- add time.{sleep_ms,sleep_us,ticks_ms,ticks_us,ticks_diff}
- reset "virtual RTC" on power on
- modutime: support float argument to time.sleep()
- add modmachine with mem* arrays
- modmachine: basic implementation of Timer for OS virtual timers
- modmachine: changing params of a timer requires disarming it first
- etshal.h: add timer functions prototypes
- modmachine: use etshal.h
- modmachine: timer: Add ONE_SHOT and PERIODIC symbolic constants
- add custom _assert() function
- implement Pin.__call__() and Pin.OPEN_DRAIN mode
- expose simple pin API at C level
- modpybpin: add support for GPIO16
- modmachine: add Pin class from modpyb
- etshal.h: more prototypes of ESP8266 SDK/BootROM functions
- support raising KeyboardInterrupt on Ctrl+C
- uart: add uart_flush() function
- allow Makefile's BAUD variable to be overridden
- enable stack overflow checking
- don't gc-collect BSS
- enable modlwip
- Makefile: add define for ESP8266 lwIP
- put more code in iROM section
- main: module to run on boot is "boot", not "main"
- move pyb.freq to machine.freq
- modnetwork: allow to configure STA and AP interfaces separately
- move wifi_mode() and phy_mode() to network module
- modnetwork: add per-interface .active() method
- modnetwork: move config defines to the top
- modnetwork: introduce interface .config() method
- modnetwork: add symbolic names for network interfaces: STA_IF & AP_IF
- add alternative event loop implementation
- feed WDT in ets_loop_iter()
- ets_alt_task: be sure to "pop" event before calling its handler
- ets_alt_task: update for vendor SDK 1.5.0
- esp_mphal: add higher-level event polling function
- define MICROPY_EVENT_POLL_HOOK for the port
- switch to lwIP built from source
- store frozen modules in FlashROM
- ets_alt_task: make FIRST_PRIO=0 to cover all task priorities
- make mp_hal_delay_us work with new event framework
- enable urandom module
- add module weak link from json to ujson
- enable more extmod's: uheapq, ure, uzlib
- enable non-blocking stream support
- add "socket" and "usocket" aliases for lwip module
- enable auto-indent in REPL
- expose pin object as a public structure for use as C pin API
- add basic I2C driver, with init and writeto methods
- modpybi2c: add missing include
- clean up bit-bang I2C implementation
- implement bit-bang I2C read, and add i2c.readfrom method
- add onewire helper functions as C module
- add tests/onewire.py as a driver and test code for ds18b20 dev
- implement software SPI class
- add PWM support
- esppwm.c: fix IRQ handler prototype
- put lexerstr32.o into FlashROM
- put utils.o to FlashROM
- link ADC class into machine module
- add esp.neopixel_write function to bit-bang WS2812 data
- tests: add neopixel.py test
- put modpybi2c.o to FlashROM
- set up UART handling task soon into init process
- modesp: flash_write(): Writes in multiples of 4 bytes
- modesp: flash_read(): Accept buffer to read to as a second argument
- README: update for the current status of the port
- enable FatFs support
- esp8266.ld: put FatFs to FlashROM
- deploy: Use --flash_size=8m option to esptool.py
- moduos: add listdir() proxy for MP_STATE_PORT(fs_user_mount)[0]
- moduos: factor out VFS method proxy helper
- moduos: add os.remove(), proxying to VFS object
- zero out fs_user_mount state on (soft) reset
- support importing modules from filesystem
- implement os.urandom function
- add basic support for duplicating REPL output
- enable uos.dupterm() method
- esp_mphal: add support for debug UART-only output
- let esp8266 "os" messages go to standard (REPL) UART
- support synchronous wifi scanning
- fix issue when current REPL line was garbage-collected
- switch back to accumulating input data via ring buffer
- implement input part of dupterm handling
- reset term_obj on reboot
- move PHY mode constants from modesp to modnetwork
- disallow recursive calls to REPL
- support dedicated REPL loop (aka pull-style)
- switch to non event-driven REPL to support paste mode
- uart: get ctrl-C working now that event-based REPL is disabled
- use VM_HOOK to call ets_loop_iter within the VM
- README: add link to docs
- move .rodata where it belongs with -mforce-l32 help
- bump iROM size to 512k
- ets_alt_task: comment out debug output
- minimize gap between Inst/DataRAM segments and FlashROM segment
- switch back to flashing combined firmware (single file)
- update flashing instructions in README
- bump heap size to 24k
- move pyb.hard_reset() to machine.reset()
- move pyb.unique_id() to machine.unique_id()
- modnetwork: require_if(): Report the actual interface required
- make destination for vendor OS debug output soft-configurable
- add initial implementation of machine.UART
- README: add short troubleshooting section
- switch from terse error messages to normal ones
- implement multistage bootstrap sequence
- add esp.freemem() and esp.meminfo() functions
- implement mp_builtin_open() using vfs_proxy_call()

examples:
- http_client.py, http_server.py aren't just unix, move to network/
- http_client.py: improve CPython compatibility in stream mode
- http_client.py: introduce main() function
- http_server.py: refactor/simplify for Python 3.5
- http_server.py: introduce main() function
- http_server.py: bind to 0.0.0.0, to be accessible from other hosts
- http_client_ssl.py: HTTPS client example

docs:
- correct WiPy Timer docs
- minor change to improve clarity in machine.Timer docs
- add note on machine.Timer class regarding PWM output pins
- correct machine.Timer code examples related to duty cycle
- add esp8266 quick reference page, with basic info
- esp8266: minor tweaks to quickref, Timer and I2C classes
- add versions.html template and support code for a version sidebar
- allow list of versions to be specified by environment variable
- esp8266: fix indent errors, typos, and add info about REPL UART
- update asm_thumb2_hints_tips re return type of asm funcs
- update details on using ADCAll object for vref/vbat channels
- add Python speed optimisation guide, including minimal viper ref
- esp8266: update quick reference: i2c.readfrom and neopixel example
- update asm tutorial, maximum number of allowed args is now 4
- update pyb.I2C constructor to reflect changes in Pyboard Lite
- mention that pyb.SPI constructor accepts "X" and "Y" arguments
- update pyb.UART.any() to mention that it returns character count
- topindex.html: refer to "pyb" module only for pyboard
- add standard modules list for esp8266
- network: esp8266: Update docs on WLAN constructor
- more standard modules for esp8266
- esp: remove getaddrinfo(), now in socket module as expected
- esp8266/quickref: note that timers supported are virtual ones
- esp8266/quickref: add note about GPIO16
- esp8266: phy_mode() moved to network module
- esp8266: esp.wifi_mode() replaced with network.WLAN.active()
- esp8266: esp.mac() replaced with network.WLAN.mac()
- correct pin interrupt example code for the WiPy
- network: esp8266: status is WLAN object method
- network: esp8266: .scan() is now synchronous and returns result list
- update copyright notice
- esp8266: esp.socket is deprecated, remove from docs
- os: change wording to be a bit more port-neutral
- machine: change wording to be a bit more port-neutral
- ubinascii: document a2b_base64(), b2a_base64()
- esp8266/quickref: add note about physical vs logical pin numbers
- ubinascii: document non-standard "sep" argument to hexlify()
- esp8266: Enable "machine" module docs

IPv6 support in unix, bignum constant folding, urandom module, faster…

… VCP

In this release there are many bug fixes and consolidation of previous
features.  Constant folding in the parser can now operate on arbitrary
precision integers, and the inline assembler is no longer restricted to
using small-ints or 30-bits.  The urandom module has been added with the
most useful random functions included.  The uhashlib module now
implements SHA1.  The Unix port supports IPv6.  The stmhal port has much
faster USB VCP for board to PC transfers, and Timer(3) is now freed up
for general purpose use by the user.

py core:
- frozenmod: make frozen module content be 0-terminated
- frozenmod: store frozen module names together, to quickly scan them
- use polymorphic iterator type where possible to reduce code size
- make dir report instance members
- implement __dict__ for instances
- objstr: in str.format, handle case of no format spec for string arg
- parse: optimise away parse node that's just parenthesis around expr
- change mp_obj_int_is_positive to more general mp_obj_int_sign
- parse: improve constant folding to operate on small and big ints
- inlinethumb: allow assembler to use big ints as args to instructions
- inlinethumb: remove 30-bit restriction on movwt instruction
- viper: truncate viper integer args so they can be up to 32-bit
- emitglue: add more feature flags to .mpy persistent bytecode output
- mpz: fix conversion of float to mpz so it works on big endian archs
- objint: fix classification of float so it works for OBJ_REPR_D
- change type of .make_new and .call args: mp_uint_t becomes size_t
- change type signature of builtin funs that take variable or kw args
- change first arg of type.make_new from mp_obj_t to mp_obj_type_t*
- emitglue: use mp_obj_is_float instead of MP_OBJ_IS_TYPE
- use new code pattern for parsing kw args with mp_arg_parse_all
- add ustruct.pack_into and unpack_from
- modmicropython: add stack_use, heap_lock and heap_unlock functions
- inlineasm: add ability to specify return type of asm_thumb funcs
- runtime: mp_stack_ctrl_init() should be called immediately on startup
- formatfloat: add ability to format doubles with exponents > 99
- builtin property: accept keyword arguments

extmod:
- moduos_dupterm: make uos.dupterm() implementation reusable
- moduos_dupterm: make mp_uos_dupterm_tx_strn() function reusable
- moduos_dupterm: handle exceptions in call to dupterm's .write()
- fix uctypes size calculation for bitfields
- modurandom: add "urandom" module
- modurandom: make yasmarang() function static
- modurandom: add some extra random functions
- moduhashlib: add support for SHA1 (based on axTLS)
- moduhashlib: use MICROPY_PY_UHASHLIB_SHA1 config define
- moductypes: implement assignment for scalar array

tests:
- uctypes: test item assignment for scalar arrays
- object_dict.py: add test for obj.__dict__
- allow float tests to run when MATH_SPECIAL_FUNCTIONS is disabled
- fix math_fun_special test so it passes with single prec float
- remove builtin_dict test
- add some tests for urandom module
- update pyboard LED test
- for pyboard, add test for I2C error handling and recovery

minimal port:
- add enough code to run minimal build on STM32F4xx hardware

unix port:
- unix_mphal: handle exceptions in call to dupterm's .read()
- unix_mphal: be sure to wrap dupterm code with MICROPY_PY_OS_DUPTERM
- modtime: strftime(): Support 2nd argument, but as time_t value
- add socket.inet_ntop function
- allow to build coverage build with OBJ_REPR_D
- add option to build 64-bit NaN-boxing interpreter
- modffi: allow to compile modffi in OBJ_REPR_D mode
- modsocket: accept(): Make IPv6-clean
- modsocket: sockaddr(): Handle AF_INET6 addresses

windows port:
- enable urandom module

stmhal port:
- make stm constants big ints when they don't fit in a small int
- remove custom mod_machine_mem_get_{read,write}_addr functions
- add os.statvfs
- add support for building frozen files
- add support for the STM32F401NUCLEO board
- make USB CDC driver use SOF instead of TIM3 for outgoing data
- make TIM3 available for use by the user
- add PWM capability for LED(3) and LED(4) on pyboards
- in HAL I2C driver, move DMA setup to after sending I2C address

docs:
- fix readthedocs build by updating Latex params
- set author as 'Damien P. George and contributors'
- add link from pyboard switch tutorial to ISR rules document
- include extra functions in time documentation for pyboard
- several minor changes: network, pyb, ADCAll and inline asm
- update to say that Timer(3) is free, and detail LED intensity

travis:
- add unix NaN-boxing build to Travis builds
- switch to Ubuntu 14.04 Trusty