diff options
Diffstat (limited to 'decoders')
| -rw-r--r-- | decoders/i2c/pd.py | 53 |
1 files changed, 26 insertions, 27 deletions
diff --git a/decoders/i2c/pd.py b/decoders/i2c/pd.py index 36c8d1e..d9061f5 100644 --- a/decoders/i2c/pd.py +++ b/decoders/i2c/pd.py @@ -21,6 +21,7 @@ # TODO: Implement support for inverting SDA/SCL levels (0->1 and 1->0). # TODO: Implement support for detecting various bus errors. +from common.srdhelper import bitpack_msb import sigrokdecode as srd ''' @@ -110,8 +111,6 @@ class Decoder(srd.Decoder): def reset(self): self.samplerate = None self.ss = self.es = self.ss_byte = -1 - self.bitcount = 0 - self.databyte = 0 self.is_write = None self.rem_addr_bytes = None self.is_repeat_start = False @@ -148,40 +147,36 @@ class Decoder(srd.Decoder): self.putp([cmd, None]) self.putx([proto[cmd][0], proto[cmd][1:]]) self.state = 'FIND ADDRESS' - self.bitcount = self.databyte = 0 self.is_repeat_start = True self.is_write = None self.rem_addr_bytes = None - self.data_bits = [] + self.data_bits.clear() # Gather 8 bits of data plus the ACK/NACK bit. def handle_address_or_data(self, pins): scl, sda = pins self.pdu_bits += 1 - # Address and data are transmitted MSB-first. - self.databyte <<= 1 - self.databyte |= sda - - # Remember the start of the first data/address bit. - if self.bitcount == 0: + # Accumulate a byte's bits, including its start position. + # Accumulate individual bits and their start/end sample numbers + # as we see them. Get the start sample number at the time when + # the bit value gets sampled. Assume the start of the next bit + # as the end sample number of the previous bit. Guess the last + # bit's end sample number from the second last bit's width. + # (gsi: Shouldn't falling SCL be the end of the bit value?) + # Keep the bits in receive order (MSB first) during accumulation. + if not self.data_bits: self.ss_byte = self.samplenum - - # Store individual bits and their start/end samplenumbers. - # In the list, index 0 represents the LSB (I²C transmits MSB-first). - self.data_bits.insert(0, [sda, self.samplenum, self.samplenum]) - if self.bitcount > 0: - self.data_bits[1][2] = self.samplenum - if self.bitcount == 7: - self.bitwidth = self.data_bits[1][2] - self.data_bits[2][2] - self.data_bits[0][2] += self.bitwidth - - # Return if we haven't collected all 8 + 1 bits, yet. - if self.bitcount < 7: - self.bitcount += 1 + if self.data_bits: + self.data_bits[-1][2] = self.samplenum + self.data_bits.append([sda, self.samplenum, self.samplenum]) + if len(self.data_bits) < 8: return + self.bitwidth = self.data_bits[-2][2] - self.data_bits[-3][2] + self.data_bits[-1][2] += self.bitwidth - d = self.databyte + # Get the byte value. Address and data are transmitted MSB-first. + d = bitpack_msb(self.data_bits, 0) if self.state == 'FIND ADDRESS': # The READ/WRITE bit is only in the first address byte, not # in data bytes. Address bit pattern 0b1111_0xxx means that @@ -225,6 +220,11 @@ class Decoder(srd.Decoder): self.ss, self.es = self.ss_byte, self.samplenum + self.bitwidth + # Reverse the list of bits to LSB first order before emitting + # annotations and passing bits to upper layers. This may be + # unexpected because the protocol is MSB first, but it keeps + # backwards compatibility. + self.data_bits.reverse() self.putp(['BITS', self.data_bits]) self.putp([cmd, d]) @@ -243,8 +243,7 @@ class Decoder(srd.Decoder): '%s: %02X' % (proto[cmd][2], d), '%02X' % d]]) # Done with this packet. - self.bitcount = self.databyte = 0 - self.data_bits = [] + self.data_bits.clear() self.state = 'FIND ACK' def get_ack(self, pins): @@ -278,7 +277,7 @@ class Decoder(srd.Decoder): self.state = 'FIND START' self.is_repeat_start = False self.is_write = None - self.data_bits = [] + self.data_bits.clear() def decode(self): while True: |