From 741dba7858f41c555d01d041c8481bf9ef155e7d Mon Sep 17 00:00:00 2001
From: Stephan Thiele <stephan.thiele@mailbox.org>
Date: Fri, 22 Feb 2019 19:29:53 +0100
Subject: can: display CRC type + correct decoding of CRC-17
---
decoders/can/pd.py | 36 ++++++++++++++++++++++++++----------
1 file changed, 26 insertions(+), 10 deletions(-)
(limited to 'decoders/can')
diff --git a/decoders/can/pd.py b/decoders/can/pd.py
index ff4c78a..2d346bb 100644
--- a/decoders/can/pd.py
+++ b/decoders/can/pd.py
@@ -162,41 +162,57 @@ class Decoder(srd.Decoder):
if bitnum == (self.last_databit + 1):
self.ss_block = self.samplenum
- # CRC sequence (15 bits)
- elif bitnum == (self.last_databit + 15):
+ if self.fd:
+ if self.dlc < 16:
+ self.crc_len = 27 # 17 + SBC + stuff bits
+ else:
+ self.crc_len = 21
+ else:
+ self.crc_len = 15
+
+ # CRC sequence (15 bits, 17 bits or 21 bits)
+ elif bitnum == (self.last_databit + self.crc_len):
+ if self.fd:
+ if self.dlc < 16:
+ crc_type = "CRC-17"
+ else:
+ crc_type = "CRC-21"
+ else:
+ crc_type = "CRC-15"
+
x = self.last_databit + 1
- crc_bits = self.bits[x:x + 15 + 1]
+ crc_bits = self.bits[x:x + self.crc_len + 1]
self.crc = int(''.join(str(d) for d in crc_bits), 2)
- self.putb([11, ['CRC sequence: 0x%04x' % self.crc,
- 'CRC: 0x%04x' % self.crc, 'CRC']])
+ self.putb([11, ['%s sequence: 0x%04x' % (crc_type, self.crc),
+ '%s: 0x%04x' % (crc_type, self.crc), '%s' % crc_type]])
if not self.is_valid_crc(crc_bits):
self.putb([16, ['CRC is invalid']])
# CRC delimiter bit (recessive)
- elif bitnum == (self.last_databit + 16):
+ elif bitnum == (self.last_databit + self.crc_len + 1):
self.putx([12, ['CRC delimiter: %d' % can_rx,
'CRC d: %d' % can_rx, 'CRC d']])
if can_rx != 1:
self.putx([16, ['CRC delimiter must be a recessive bit']])
# ACK slot bit (dominant: ACK, recessive: NACK)
- elif bitnum == (self.last_databit + 17):
+ elif bitnum == (self.last_databit + self.crc_len + 2):
ack = 'ACK' if can_rx == 0 else 'NACK'
self.putx([13, ['ACK slot: %s' % ack, 'ACK s: %s' % ack, 'ACK s']])
# ACK delimiter bit (recessive)
- elif bitnum == (self.last_databit + 18):
+ elif bitnum == (self.last_databit + self.crc_len + 3):
self.putx([14, ['ACK delimiter: %d' % can_rx,
'ACK d: %d' % can_rx, 'ACK d']])
if can_rx != 1:
self.putx([16, ['ACK delimiter must be a recessive bit']])
# Remember start of EOF (see below).
- elif bitnum == (self.last_databit + 19):
+ elif bitnum == (self.last_databit + self.crc_len + 4):
self.ss_block = self.samplenum
# End of frame (EOF), 7 recessive bits
- elif bitnum == (self.last_databit + 25):
+ elif bitnum == (self.last_databit + self.crc_len + 11):
self.putb([2, ['End of frame', 'EOF', 'E']])
if self.rawbits[-7:] != [1, 1, 1, 1, 1, 1, 1]:
self.putb([16, ['End of frame (EOF) must be 7 recessive bits']])
--
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