This project shows how to use GD32VF103 board as USBtoUART bridge.
The project is intended to be run on Longan Nano board.
If testing on another board (without a display), editlib/usbcdc/include/cdc_acm_core.hto remove display and/or LED support.
- The project implements USB CDC/ACM device with some additional features.
- Bridging USB to two UARTS is supported.
- Display support, displays status and statistics.
- Baudrates from 2400 ~ 4000000 Bd are supported
- Python CDC driver with examples included
UART0:
PA9 TxPA10 RxPA13 RTSPA14 DTR
UART1:
PB10 TxPB11 RxPB13 RTSPB14 DTR
After the board is connected to PC it will be enumerated as USB device 28e9:018a.
Bus 003 Device 028: ID 28e9:018a
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 2 Communications
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 64
idVendor 0x28e9
idProduct 0x018a
bcdDevice 1.00
iManufacturer 1 GigaDevice
iProduct 2 GD32VF USB CDC ACM in FS Mode
iSerial 3 GD32VF-3.0.0-012020
bNumConfigurations 1
...
The device can be accessed for serial communication as /dev/ttyACMn, for example via Minicom, Putty etc.
[24377.013615] usb 3-9: new full-speed USB device number 28 using xhci_hcd
[24377.167007] usb 3-9: New USB device found, idVendor=28e9, idProduct=018a, bcdDevice= 1.00
[24377.167011] usb 3-9: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[24377.167013] usb 3-9: Product: GD32VF USB CDC ACM in FS Mode
[24377.167015] usb 3-9: Manufacturer: GigaDevice
[24377.167017] usb 3-9: SerialNumber: GD32VF-3.0.0-012020
[24377.168506] cdc_acm 3-9:1.0: ttyACM0: USB ACM device
As the device has some non-standard CDC features, it is recommended to use it via the provided Python driver cdc_driver.py.
GD32VF103 does not have enough USB endpoints to implement a composite CDC device.
The UART ports can be changed using one of two methods:
- sending a
breakcondition, this is usually used from standard communication program - sending a special CDC command, this is fully supported and described in
cdc_driver.py
If Longan Nano is used and USE_LEDS is enabled in configuration, green LED will be active when UART1 is selected.
If Longan Nano is used and USE_DISPLAY is enabled in configuration, UART format and DTR/RTS status will be shown on display.
Special CDC command can be used to display the communication statistics (USB number of sent/received bytes, UART number of sent/received byted, number of UART receive errors,...).
DTR and RTS outputs can be configured as push-pull or open colector (UARTn_RTS_DTR_MODE define in lib/usbcdc/include/cdc_acm_core.h).
Using break for UART change can be disabled/enabled using UART_USE_BREAK_TO_CHANGE define in lib/usbcdc/include/cdc_acm_core.h.
# -------------------------------------------------------
# Show the current status on the device display (if used)
# If the 'reset' argument is 1, reset the counters
# -------------------------------------------------------
showStatus(reset = 0)
# -----------------------------------
# Set DTR and RTS line state
# -----------------------------------
setLineState(dtr=1, rts=1)
# ------------------------------------------------------
# Set active device UART, 0 or 1 can be used as argument
# ------------------------------------------------------
setUART(uartno=0)
# -----------------------------------------------------------
# Set the UART communication format
# bdr: baudrate, 2400 - 4000000
# bits: 8 or 7
# parity: 0 - None; 2 - Even, 3 - Odd
# stop: number of stop bits; 0 = 1, 1 = 0.5, 2 = 2, 3 = 1.5
# -----------------------------------------------------------
setFormat(bdr=115200, bits=8, parity=0, stop=0)
# ----------------------------------------------------------
# Get the current UART communication format from the device
# If 'prn' argument is True, prints the format
# Returns tuple: (bdr, stop, parity, bits)
# ----------------------------------------------------------
getFormat(prn=False)
# --------------------------------------------
# Get the current transmition status
# If 'prn' argument is True, prints the status
# Returns tuple:
# (
# active_uart,
# dtr_state,
# rts_state,
# usb_sent,
# usb_received,
# uart_sent,
# uart_received,
# uart_receive_errors
# )
# --------------------------------------------
getStatus(prn=False)
# -------------------------------------------------
# Return number of received bytes in receive buffer
# -------------------------------------------------
received()
# ----------------------------------
# Read data from receive buffer
# count: max number of bytes to read
# Returns array of bytes
# ----------------------------------
read(count=1)
# -------------------------------------------------
# Read data from receive buffer converted to string
# count: max number of bytes to read
# -------------------------------------------------
readString(count=1)
# --------------------
# Write data
# --------------------
write(data)