sdq: Add the SDQ protocol decoder

[ gsi: minor whitespace adjustment ]
sigrokproject · Aug 12, 2020 · b094e81 · b094e81
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diff --git a/decoders/sdq/__init__.py b/decoders/sdq/__init__.py
@@ -0,0 +1,24 @@
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2019-2020 Philip Åkesson <philip.akesson@gmail.com>
+##
+## This program is free software; you can redistribute it and/or modify
+## it under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 2 of the License, or
+## (at your option) any later version.
+##
+## This program is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+## GNU General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with this program; if not, see <http://www.gnu.org/licenses/>.
+##
+
+'''
+Texas Instruments SDQ protocol, also used by Apple.
+'''
+
+from .pd import Decoder
diff --git a/decoders/sdq/pd.py b/decoders/sdq/pd.py
@@ -0,0 +1,131 @@
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2019-2020 Philip Åkesson <philip.akesson@gmail.com>
+##
+## This program is free software; you can redistribute it and/or modify
+## it under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 2 of the License, or
+## (at your option) any later version.
+##
+## This program is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+## GNU General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with this program; if not, see <http://www.gnu.org/licenses/>.
+##
+
+import sigrokdecode as srd
+
+class SamplerateError(Exception):
+    pass
+
+class Decoder(srd.Decoder):
+    api_version = 3
+    id = 'sdq'
+    name = 'SDQ'
+    longname = 'Texas Instruments SDQ'
+    desc = 'Texas Instruments SDQ. The SDQ protocol is also used by Apple.'
+    license = 'gplv2+'
+    inputs = ['logic']
+    outputs = []
+    tags = ['Embedded/industrial']
+    channels = (
+        {'id': 'sdq', 'name': 'SDQ', 'desc': 'Single wire SDQ data line.'},
+    )
+    options = (
+        {'id': 'bitrate', 'desc': 'Bit rate', 'default': 98425},
+    )
+    annotations = (
+        ('bit', 'Bit'),
+        ('byte', 'Byte'),
+        ('break', 'Break'),
+    )
+    annotation_rows = (
+        ('bits', 'Bits', (0,)),
+        ('bytes', 'Bytes', (1,)),
+        ('breaks', 'Breaks', (2,)),
+    )
+
+    def puts(self, data):
+        self.put(self.startsample, self.samplenum, self.out_ann, data)
+
+    def putetu(self, data):
+        self.put(self.startsample, self.startsample + int(self.bit_width), self.out_ann, data)
+
+    def putbetu(self, data):
+        self.put(self.bytepos, self.startsample + int(self.bit_width), self.out_ann, data)
+
+    def bits2num(self, bitlist):
+        number = 0
+        for i in range(len(bitlist)):
+            number += bitlist[i] * 2**i
+        return number
+
+    def __init__(self):
+        self.reset()
+
+    def reset(self):
+        self.samplerate = None
+        self.state = 'INIT'
+        self.startsample = 0
+        self.bits = []
+        self.bytepos = 0
+
+    def start(self):
+        self.out_ann = self.register(srd.OUTPUT_ANN)
+
+    def metadata(self, key, value):
+        if key == srd.SRD_CONF_SAMPLERATE:
+            self.samplerate = value
+            self.bit_width = float(self.samplerate) / float(self.options['bitrate'])
+            self.half_bit_width = self.bit_width / 2.0
+            self.break_threshold = self.bit_width * 1.2 # Break if the line is low for longer than this
+
+    def handle_bit(self, bit):
+        self.bits.append(bit)
+        self.putetu([0, ['Bit: %d' % bit, '%d' % bit]])
+
+        if len(self.bits) == 8:
+            byte = self.bits2num(self.bits)
+            self.putbetu([1, ['Byte: %#04x' % byte, '%#04x' % byte]])
+            self.bits = []
+            self.bytepos = 0
+
+    def handle_break(self):
+        self.puts([2, ['Break', 'BR']])
+        self.bits = []
+        self.startsample = self.samplenum
+        self.bytepos = 0
+
+    def decode(self):
+        if not self.samplerate:
+            raise SamplerateError('Cannot decode without samplerate.')
+
+        while True:
+            if self.state == 'INIT':
+                sdq, = self.wait({0: 'h'}) # Wait until the line is high before starting
+                self.state = 'DATA'
+
+            elif self.state == 'DATA':
+                sdq, = self.wait({0: 'f'}) # Falling edge
+
+                self.startsample = self.samplenum
+                if self.bytepos == 0:
+                    self.bytepos = self.samplenum
+
+                sdq, = self.wait({0: 'r'}) # Rising edge
+
+                delta = self.samplenum - self.startsample
+                if delta > self.break_threshold:
+                    self.state = 'BREAK'
+                elif delta > self.half_bit_width:
+                    self.handle_bit(0)
+                else:
+                    self.handle_bit(1)
+
+            elif self.state == 'BREAK':
+                self.handle_break()
+                self.state = 'DATA'