2 ## This file is part of the libsigrokdecode project.
4 ## Copyright (C) 2012-2013 Uwe Hermann <uwe@hermann-uwe.de>
5 ## Copyright (C) 2019 Stephan Thiele <stephan.thiele@mailbox.org>
7 ## This program is free software; you can redistribute it and/or modify
8 ## it under the terms of the GNU General Public License as published by
9 ## the Free Software Foundation; either version 2 of the License, or
10 ## (at your option) any later version.
12 ## This program is distributed in the hope that it will be useful,
13 ## but WITHOUT ANY WARRANTY; without even the implied warranty of
14 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 ## GNU General Public License for more details.
17 ## You should have received a copy of the GNU General Public License
18 ## along with this program; if not, see <http://www.gnu.org/licenses/>.
21 import sigrokdecode as srd
23 class SamplerateError(Exception):
27 return [0, 1, 2, 3, 4, 5, 6, 7, 8, 12, 16, 20, 24, 32, 48, 64][dlc]
29 class Decoder(srd.Decoder):
33 longname = 'Controller Area Network'
34 desc = 'Field bus protocol for distributed realtime control.'
40 {'id': 'can_rx', 'name': 'CAN RX', 'desc': 'CAN bus line'},
43 {'id': 'nominal_bitrate', 'desc': 'Nominal bitrate (bits/s)', 'default': 1000000},
44 {'id': 'fast_bitrate', 'desc': 'Fast bitrate (bits/s)', 'default': 2000000},
45 {'id': 'sample_point', 'desc': 'Sample point (%)', 'default': 70.0},
48 ('data', 'Payload data'),
49 ('sof', 'Start of frame'),
50 ('eof', 'End of frame'),
52 ('ext-id', 'Extended identifier'),
53 ('full-id', 'Full identifier'),
54 ('ide', 'Identifier extension bit'),
55 ('reserved-bit', 'Reserved bit 0 and 1'),
56 ('rtr', 'Remote transmission request'),
57 ('srr', 'Substitute remote request'),
58 ('dlc', 'Data length count'),
59 ('crc-sequence', 'CRC sequence'),
60 ('crc-delimiter', 'CRC delimiter'),
61 ('ack-slot', 'ACK slot'),
62 ('ack-delimiter', 'ACK delimiter'),
63 ('stuff-bit', 'Stuff bit'),
64 ('warning', 'Warning'),
68 ('bits', 'Bits', (15, 17)),
69 ('fields', 'Fields', tuple(range(15))),
70 ('warnings', 'Warnings', (16,)),
77 self.samplerate = None
78 self.reset_variables()
81 self.out_ann = self.register(srd.OUTPUT_ANN)
82 self.out_python = self.register(srd.OUTPUT_PYTHON)
84 def set_bit_rate(self, bitrate):
85 self.bit_width = float(self.samplerate) / float(bitrate)
86 self.sample_point = (self.bit_width / 100.0) * self.options['sample_point']
88 def set_nominal_bitrate(self):
89 self.set_bit_rate(self.options['nominal_bitrate'])
91 def set_fast_bitrate(self):
92 self.set_bit_rate(self.options['fast_bitrate'])
94 def metadata(self, key, value):
95 if key == srd.SRD_CONF_SAMPLERATE:
96 self.samplerate = value
97 self.bit_width = float(self.samplerate) / float(self.options['nominal_bitrate'])
98 self.sample_point = (self.bit_width / 100.0) * self.options['sample_point']
100 # Generic helper for CAN bit annotations.
101 def putg(self, ss, es, data):
102 left, right = int(self.sample_point), int(self.bit_width - self.sample_point)
103 self.put(ss - left, es + right, self.out_ann, data)
105 # Single-CAN-bit annotation using the current samplenum.
106 def putx(self, data):
107 self.putg(self.samplenum, self.samplenum, data)
109 # Single-CAN-bit annotation using the samplenum of CAN bit 12.
110 def put12(self, data):
111 self.putg(self.ss_bit12, self.ss_bit12, data)
113 # Single-CAN-bit annotation using the samplenum of CAN bit 32.
114 def put32(self, data):
115 self.putg(self.ss_bit32, self.ss_bit32, data)
117 # Multi-CAN-bit annotation from self.ss_block to current samplenum.
118 def putb(self, data):
119 self.putg(self.ss_block, self.samplenum, data)
121 def putpp(self, data):
122 self.put(self.ss_packet, self.es_packet, self.out_python, data)
124 def reset_variables(self):
126 self.sof = self.frame_type = self.dlc = None
127 self.rawbits = [] # All bits, including stuff bits
128 self.bits = [] # Only actual CAN frame bits (no stuff bits)
129 self.curbit = 0 # Current bit of CAN frame (bit 0 == SOF)
130 self.last_databit = 999 # Positive value that bitnum+x will never match
134 self.ss_databytebits = []
140 # Poor man's clock synchronization. Use signal edges which change to
141 # dominant state in rather simple ways. This naive approach is neither
142 # aware of the SYNC phase's width nor the specific location of the edge,
143 # but improves the decoder's reliability when the input signal's bitrate
144 # does not exactly match the nominal rate.
145 def dom_edge_seen(self, force = False):
146 self.dom_edge_snum = self.samplenum
147 self.dom_edge_bcount = self.curbit
149 # Determine the position of the next desired bit's sample point.
150 def get_sample_point(self, bitnum):
151 samplenum = self.dom_edge_snum
152 samplenum += self.bit_width * (bitnum - self.dom_edge_bcount)
153 samplenum += self.sample_point
154 return int(samplenum)
156 def is_stuff_bit(self):
157 # CAN uses NRZ encoding and bit stuffing.
158 # After 5 identical bits, a stuff bit of opposite value is added.
159 # But not in the CRC delimiter, ACK, and end of frame fields.
160 if len(self.bits) > self.last_databit + 17:
162 last_6_bits = self.rawbits[-6:]
163 if last_6_bits not in ([0, 0, 0, 0, 0, 1], [1, 1, 1, 1, 1, 0]):
166 # Stuff bit. Keep it in self.rawbits, but drop it from self.bits.
167 self.bits.pop() # Drop last bit.
170 def is_valid_crc(self, crc_bits):
173 def decode_error_frame(self, bits):
176 def decode_overload_frame(self, bits):
179 # Both standard and extended frames end with CRC, CRC delimiter, ACK,
180 # ACK delimiter, and EOF fields. Handle them in a common function.
181 # Returns True if the frame ended (EOF), False otherwise.
182 def decode_frame_end(self, can_rx, bitnum):
184 # Remember start of CRC sequence (see below).
185 if bitnum == (self.last_databit + 1):
186 self.ss_block = self.samplenum
188 if dlc2len(self.dlc) < 16:
189 self.crc_len = 27 # 17 + SBC + stuff bits
191 self.crc_len = 32 # 21 + SBC + stuff bits
195 # CRC sequence (15 bits, 17 bits or 21 bits)
196 elif bitnum == (self.last_databit + self.crc_len):
198 if dlc2len(self.dlc) < 16:
205 x = self.last_databit + 1
206 crc_bits = self.bits[x:x + self.crc_len + 1]
207 self.crc = int(''.join(str(d) for d in crc_bits), 2)
208 self.putb([11, ['%s sequence: 0x%04x' % (crc_type, self.crc),
209 '%s: 0x%04x' % (crc_type, self.crc), '%s' % crc_type]])
210 if not self.is_valid_crc(crc_bits):
211 self.putb([16, ['CRC is invalid']])
213 # CRC delimiter bit (recessive)
214 elif bitnum == (self.last_databit + self.crc_len + 1):
215 self.putx([12, ['CRC delimiter: %d' % can_rx,
216 'CRC d: %d' % can_rx, 'CRC d']])
218 self.putx([16, ['CRC delimiter must be a recessive bit']])
221 self.set_nominal_bitrate()
223 # ACK slot bit (dominant: ACK, recessive: NACK)
224 elif bitnum == (self.last_databit + self.crc_len + 2):
225 ack = 'ACK' if can_rx == 0 else 'NACK'
226 self.putx([13, ['ACK slot: %s' % ack, 'ACK s: %s' % ack, 'ACK s']])
228 # ACK delimiter bit (recessive)
229 elif bitnum == (self.last_databit + self.crc_len + 3):
230 self.putx([14, ['ACK delimiter: %d' % can_rx,
231 'ACK d: %d' % can_rx, 'ACK d']])
233 self.putx([16, ['ACK delimiter must be a recessive bit']])
235 # Remember start of EOF (see below).
236 elif bitnum == (self.last_databit + self.crc_len + 4):
237 self.ss_block = self.samplenum
239 # End of frame (EOF), 7 recessive bits
240 elif bitnum == (self.last_databit + self.crc_len + 10):
241 self.putb([2, ['End of frame', 'EOF', 'E']])
242 if self.rawbits[-7:] != [1, 1, 1, 1, 1, 1, 1]:
243 self.putb([16, ['End of frame (EOF) must be 7 recessive bits']])
244 self.es_packet = self.samplenum
245 self.putpp((self.frame_type, self.fullid, self.rtr_type, self.dlc, self.bytes))
246 self.reset_variables()
251 # Returns True if the frame ended (EOF), False otherwise.
252 def decode_standard_frame(self, can_rx, bitnum):
254 # Bit 14: FDF (Flexible data format)
255 # Has to be sent dominant when FD frame, has to be sent recessive
256 # when classic CAN frame.
258 self.fd = True if can_rx else False
260 self.putx([7, ['Flexible data format: %d' % can_rx,
261 'FDF: %d' % can_rx, 'FDF']])
263 self.putx([7, ['Reserved bit 0: %d' % can_rx,
264 'RB0: %d' % can_rx, 'RB0']])
267 # Bit 12: Substitute remote request (SRR) bit
268 self.put12([8, ['Substitute remote request', 'SRR']])
271 # Bit 12: Remote transmission request (RTR) bit
272 # Data frame: dominant, remote frame: recessive
273 # Remote frames do not contain a data field.
274 self.rtr_type = 'remote' if self.bits[12] == 1 else 'data'
275 self.put12([8, ['Remote transmission request: %s frame' % self.rtr_type,
276 'RTR: %s frame' % self.rtr_type, 'RTR']])
279 if bitnum == 15 and self.fd:
280 self.putx([7, ['Reserved: %d' % can_rx, 'R0: %d' % can_rx, 'R0']])
282 if bitnum == 16 and self.fd:
283 self.putx([7, ['Bit rate switch: %d' % can_rx, 'BRS: %d' % can_rx, 'BRS']])
285 if bitnum == 17 and self.fd:
286 self.putx([7, ['Error state indicator: %d' % can_rx, 'ESI: %d' % can_rx, 'ESI']])
288 # Remember start of DLC (see below).
289 elif bitnum == self.dlc_start:
290 self.ss_block = self.samplenum
292 # Bits 15-18: Data length code (DLC), in number of bytes (0-8).
293 elif bitnum == self.dlc_start + 3:
294 self.dlc = int(''.join(str(d) for d in self.bits[self.dlc_start:self.dlc_start + 4]), 2)
295 self.putb([10, ['Data length code: %d' % self.dlc,
296 'DLC: %d' % self.dlc, 'DLC']])
297 self.last_databit = self.dlc_start + 3 + (dlc2len(self.dlc) * 8)
298 if self.dlc > 8 and not self.fd:
299 self.putb([16, ['Data length code (DLC) > 8 is not allowed']])
301 # Remember all databyte bits, except the very last one.
302 elif bitnum in range(self.dlc_start + 4, self.last_databit):
303 self.ss_databytebits.append(self.samplenum)
305 # Bits 19-X: Data field (0-8 bytes, depending on DLC)
306 # The bits within a data byte are transferred MSB-first.
307 elif bitnum == self.last_databit:
308 self.ss_databytebits.append(self.samplenum) # Last databyte bit.
309 for i in range(dlc2len(self.dlc)):
310 x = self.dlc_start + 4 + (8 * i)
311 b = int(''.join(str(d) for d in self.bits[x:x + 8]), 2)
313 ss = self.ss_databytebits[i * 8]
314 es = self.ss_databytebits[((i + 1) * 8) - 1]
315 self.putg(ss, es, [0, ['Data byte %d: 0x%02x' % (i, b),
316 'DB %d: 0x%02x' % (i, b), 'DB']])
317 self.ss_databytebits = []
319 elif bitnum > self.last_databit:
320 return self.decode_frame_end(can_rx, bitnum)
324 # Returns True if the frame ended (EOF), False otherwise.
325 def decode_extended_frame(self, can_rx, bitnum):
327 # Remember start of EID (see below).
329 self.ss_block = self.samplenum
333 # Bits 14-31: Extended identifier (EID[17..0])
335 self.eid = int(''.join(str(d) for d in self.bits[14:]), 2)
336 s = '%d (0x%x)' % (self.eid, self.eid)
337 self.putb([4, ['Extended Identifier: %s' % s,
338 'Extended ID: %s' % s, 'Extended ID', 'EID']])
340 self.fullid = self.id << 18 | self.eid
341 s = '%d (0x%x)' % (self.fullid, self.fullid)
342 self.putb([5, ['Full Identifier: %s' % s, 'Full ID: %s' % s,
345 # Bit 12: Substitute remote request (SRR) bit
346 self.put12([9, ['Substitute remote request: %d' % self.bits[12],
347 'SRR: %d' % self.bits[12], 'SRR']])
349 # Bit 32: Remote transmission request (RTR) bit
350 # Data frame: dominant, remote frame: recessive
351 # Remote frames do not contain a data field.
353 # Remember start of RTR (see below).
355 self.ss_bit32 = self.samplenum
359 self.rtr_type = 'remote' if can_rx == 1 else 'data'
360 self.putx([8, ['Remote transmission request: %s frame' % self.rtr_type,
361 'RTR: %s frame' % self.rtr_type, 'RTR']])
363 # Bit 33: RB1 (reserved bit)
365 self.fd = True if can_rx else False
368 self.putx([7, ['Flexible data format: %d' % can_rx,
369 'FDF: %d' % can_rx, 'FDF']])
370 self.put32([7, ['Reserved bit 1: %d' % self.rtr,
371 'RB1: %d' % self.rtr, 'RB1']])
373 self.putx([7, ['Reserved bit 1: %d' % can_rx,
374 'RB1: %d' % can_rx, 'RB1']])
376 # Bit 34: RB0 (reserved bit)
378 self.putx([7, ['Reserved bit 0: %d' % can_rx,
379 'RB0: %d' % can_rx, 'RB0']])
381 elif bitnum == 35 and self.fd:
382 self.putx([7, ['Bit rate switch: %d' % can_rx,
383 'BRS: %d' % can_rx, 'BRS']])
385 elif bitnum == 36 and self.fd:
386 self.putx([7, ['Error state indicator: %d' % can_rx,
387 'ESI: %d' % can_rx, 'ESI']])
389 # Remember start of DLC (see below).
390 elif bitnum == self.dlc_start:
391 self.ss_block = self.samplenum
393 # Bits 35-38: Data length code (DLC), in number of bytes (0-8).
394 elif bitnum == self.dlc_start + 3:
395 self.dlc = int(''.join(str(d) for d in self.bits[self.dlc_start:self.dlc_start + 4]), 2)
396 self.putb([10, ['Data length code: %d' % self.dlc,
397 'DLC: %d' % self.dlc, 'DLC']])
398 self.last_databit = self.dlc_start + 3 + (dlc2len(self.dlc) * 8)
400 # Remember all databyte bits, except the very last one.
401 elif bitnum in range(self.dlc_start + 4, self.last_databit):
402 self.ss_databytebits.append(self.samplenum)
404 # Bits 39-X: Data field (0-8 bytes, depending on DLC)
405 # The bits within a data byte are transferred MSB-first.
406 elif bitnum == self.last_databit:
407 self.ss_databytebits.append(self.samplenum) # Last databyte bit.
408 for i in range(dlc2len(self.dlc)):
409 x = self.dlc_start + 4 + (8 * i)
410 b = int(''.join(str(d) for d in self.bits[x:x + 8]), 2)
412 ss = self.ss_databytebits[i * 8]
413 es = self.ss_databytebits[((i + 1) * 8) - 1]
414 self.putg(ss, es, [0, ['Data byte %d: 0x%02x' % (i, b),
415 'DB %d: 0x%02x' % (i, b), 'DB']])
416 self.ss_databytebits = []
418 elif bitnum > self.last_databit:
419 return self.decode_frame_end(can_rx, bitnum)
423 def handle_bit(self, can_rx):
424 self.rawbits.append(can_rx)
425 self.bits.append(can_rx)
427 # Get the index of the current CAN frame bit (without stuff bits).
428 bitnum = len(self.bits) - 1
430 if self.fd and can_rx:
431 if bitnum == 16 and self.frame_type == 'standard' \
432 or bitnum == 35 and self.frame_type == 'extended':
433 self.dom_edge_seen(force=True)
434 self.set_fast_bitrate()
436 # If this is a stuff bit, remove it from self.bits and ignore it.
437 if self.is_stuff_bit():
438 self.putx([15, [str(can_rx)]])
439 self.curbit += 1 # Increase self.curbit (bitnum is not affected).
442 self.putx([17, [str(can_rx)]])
444 # Bit 0: Start of frame (SOF) bit
446 self.ss_packet = self.samplenum
447 self.putx([1, ['Start of frame', 'SOF', 'S']])
449 self.putx([16, ['Start of frame (SOF) must be a dominant bit']])
451 # Remember start of ID (see below).
453 self.ss_block = self.samplenum
455 # Bits 1-11: Identifier (ID[10..0])
456 # The bits ID[10..4] must NOT be all recessive.
458 self.id = int(''.join(str(d) for d in self.bits[1:]), 2)
459 self.fullid = self.id
460 s = '%d (0x%x)' % (self.id, self.id),
461 self.putb([3, ['Identifier: %s' % s, 'ID: %s' % s, 'ID']])
462 if (self.id & 0x7f0) == 0x7f0:
463 self.putb([16, ['Identifier bits 10..4 must not be all recessive']])
465 # RTR or SRR bit, depending on frame type (gets handled later).
467 # self.putx([0, ['RTR/SRR: %d' % can_rx]]) # Debug only.
468 self.ss_bit12 = self.samplenum
470 # Bit 13: Identifier extension (IDE) bit
471 # Standard frame: dominant, extended frame: recessive
473 ide = self.frame_type = 'standard' if can_rx == 0 else 'extended'
474 self.putx([6, ['Identifier extension bit: %s frame' % ide,
475 'IDE: %s frame' % ide, 'IDE']])
477 # Bits 14-X: Frame-type dependent, passed to the resp. handlers.
479 if self.frame_type == 'standard':
480 done = self.decode_standard_frame(can_rx, bitnum)
482 done = self.decode_extended_frame(can_rx, bitnum)
484 # The handlers return True if a frame ended (EOF).
488 # After a frame there are 3 intermission bits (recessive).
489 # After these bits, the bus is considered free.
494 if not self.samplerate:
495 raise SamplerateError('Cannot decode without samplerate.')
499 if self.state == 'IDLE':
500 # Wait for a dominant state (logic 0) on the bus.
501 (can_rx,) = self.wait({0: 'l'})
502 self.sof = self.samplenum
503 self.dom_edge_seen(force = True)
504 self.state = 'GET BITS'
505 elif self.state == 'GET BITS':
506 # Wait until we're in the correct bit/sampling position.
507 pos = self.get_sample_point(self.curbit)
508 (can_rx,) = self.wait([{'skip': pos - self.samplenum}, {0: 'f'}])
512 self.handle_bit(can_rx)