2 ## This file is part of the libsigrokdecode project.
4 ## Copyright (C) 2012-2013 Uwe Hermann <uwe@hermann-uwe.de>
6 ## This program is free software; you can redistribute it and/or modify
7 ## it under the terms of the GNU General Public License as published by
8 ## the Free Software Foundation; either version 2 of the License, or
9 ## (at your option) any later version.
11 ## This program is distributed in the hope that it will be useful,
12 ## but WITHOUT ANY WARRANTY; without even the implied warranty of
13 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 ## GNU General Public License for more details.
16 ## You should have received a copy of the GNU General Public License
17 ## along with this program; if not, see <http://www.gnu.org/licenses/>.
20 import sigrokdecode as srd
22 class SamplerateError(Exception):
25 class Decoder(srd.Decoder):
29 longname = 'Controller Area Network'
30 desc = 'Field bus protocol for distributed realtime control.'
35 {'id': 'can_rx', 'name': 'CAN RX', 'desc': 'CAN bus line'},
38 {'id': 'bitrate', 'desc': 'Bitrate (bits/s)', 'default': 1000000},
39 {'id': 'sample_point', 'desc': 'Sample point (%)', 'default': 70.0},
42 ('data', 'CAN payload data'),
43 ('sof', 'Start of frame'),
44 ('eof', 'End of frame'),
46 ('ext-id', 'Extended identifier'),
47 ('full-id', 'Full identifier'),
48 ('ide', 'Identifier extension bit'),
49 ('reserved-bit', 'Reserved bit 0 and 1'),
50 ('rtr', 'Remote transmission request'),
51 ('srr', 'Substitute remote request'),
52 ('dlc', 'Data length count'),
53 ('crc-sequence', 'CRC sequence'),
54 ('crc-delimiter', 'CRC delimiter'),
55 ('ack-slot', 'ACK slot'),
56 ('ack-delimiter', 'ACK delimiter'),
57 ('stuff-bit', 'Stuff bit'),
58 ('warnings', 'Human-readable warnings'),
62 ('bits', 'Bits', (15, 17)),
63 ('fields', 'Fields', tuple(range(15))),
64 ('warnings', 'Warnings', (16,)),
68 self.samplerate = None
69 self.reset_variables()
72 self.out_ann = self.register(srd.OUTPUT_ANN)
74 def metadata(self, key, value):
75 if key == srd.SRD_CONF_SAMPLERATE:
76 self.samplerate = value
77 self.bit_width = float(self.samplerate) / float(self.options['bitrate'])
78 self.bitpos = (self.bit_width / 100.0) * self.options['sample_point']
80 # Generic helper for CAN bit annotations.
81 def putg(self, ss, es, data):
82 left, right = int(self.bitpos), int(self.bit_width - self.bitpos)
83 self.put(ss - left, es + right, self.out_ann, data)
85 # Single-CAN-bit annotation using the current samplenum.
87 self.putg(self.samplenum, self.samplenum, data)
89 # Single-CAN-bit annotation using the samplenum of CAN bit 12.
90 def put12(self, data):
91 self.putg(self.ss_bit12, self.ss_bit12, data)
93 # Multi-CAN-bit annotation from self.ss_block to current samplenum.
95 self.putg(self.ss_block, self.samplenum, data)
97 def reset_variables(self):
99 self.sof = self.frame_type = self.dlc = None
100 self.rawbits = [] # All bits, including stuff bits
101 self.bits = [] # Only actual CAN frame bits (no stuff bits)
102 self.curbit = 0 # Current bit of CAN frame (bit 0 == SOF)
103 self.last_databit = 999 # Positive value that bitnum+x will never match
106 self.ss_databytebits = []
108 # Determine the position of the next desired bit's sample point.
109 def get_sample_point(self, bitnum):
110 bitpos = int(self.sof + (self.bit_width * bitnum) + self.bitpos)
113 def is_stuff_bit(self):
114 # CAN uses NRZ encoding and bit stuffing.
115 # After 5 identical bits, a stuff bit of opposite value is added.
116 # But not in the CRC delimiter, ACK, and end of frame fields.
117 if len(self.bits) > self.last_databit + 16:
119 last_6_bits = self.rawbits[-6:]
120 if last_6_bits not in ([0, 0, 0, 0, 0, 1], [1, 1, 1, 1, 1, 0]):
123 # Stuff bit. Keep it in self.rawbits, but drop it from self.bits.
124 self.bits.pop() # Drop last bit.
127 def is_valid_crc(self, crc_bits):
130 def decode_error_frame(self, bits):
133 def decode_overload_frame(self, bits):
136 # Both standard and extended frames end with CRC, CRC delimiter, ACK,
137 # ACK delimiter, and EOF fields. Handle them in a common function.
138 # Returns True if the frame ended (EOF), False otherwise.
139 def decode_frame_end(self, can_rx, bitnum):
141 # Remember start of CRC sequence (see below).
142 if bitnum == (self.last_databit + 1):
143 self.ss_block = self.samplenum
145 # CRC sequence (15 bits)
146 elif bitnum == (self.last_databit + 15):
147 x = self.last_databit + 1
148 crc_bits = self.bits[x:x + 15 + 1]
149 self.crc = int(''.join(str(d) for d in crc_bits), 2)
150 self.putb([11, ['CRC sequence: 0x%04x' % self.crc,
151 'CRC: 0x%04x' % self.crc, 'CRC']])
152 if not self.is_valid_crc(crc_bits):
153 self.putb([16, ['CRC is invalid']])
155 # CRC delimiter bit (recessive)
156 elif bitnum == (self.last_databit + 16):
157 self.putx([12, ['CRC delimiter: %d' % can_rx,
158 'CRC d: %d' % can_rx, 'CRC d']])
160 self.putx([16, ['CRC delimiter must be a recessive bit']])
162 # ACK slot bit (dominant: ACK, recessive: NACK)
163 elif bitnum == (self.last_databit + 17):
164 ack = 'ACK' if can_rx == 0 else 'NACK'
165 self.putx([13, ['ACK slot: %s' % ack, 'ACK s: %s' % ack, 'ACK s']])
167 # ACK delimiter bit (recessive)
168 elif bitnum == (self.last_databit + 18):
169 self.putx([14, ['ACK delimiter: %d' % can_rx,
170 'ACK d: %d' % can_rx, 'ACK d']])
172 self.putx([16, ['ACK delimiter must be a recessive bit']])
174 # Remember start of EOF (see below).
175 elif bitnum == (self.last_databit + 19):
176 self.ss_block = self.samplenum
178 # End of frame (EOF), 7 recessive bits
179 elif bitnum == (self.last_databit + 25):
180 self.putb([2, ['End of frame', 'EOF', 'E']])
181 if self.rawbits[-7:] != [1, 1, 1, 1, 1, 1, 1]:
182 self.putb([16, ['End of frame (EOF) must be 7 recessive bits']])
183 self.reset_variables()
188 # Returns True if the frame ended (EOF), False otherwise.
189 def decode_standard_frame(self, can_rx, bitnum):
191 # Bit 14: RB0 (reserved bit)
192 # Has to be sent dominant, but receivers should accept recessive too.
194 self.putx([7, ['Reserved bit 0: %d' % can_rx,
195 'RB0: %d' % can_rx, 'RB0']])
197 # Bit 12: Remote transmission request (RTR) bit
198 # Data frame: dominant, remote frame: recessive
199 # Remote frames do not contain a data field.
200 rtr = 'remote' if self.bits[12] == 1 else 'data'
201 self.put12([8, ['Remote transmission request: %s frame' % rtr,
202 'RTR: %s frame' % rtr, 'RTR']])
204 # Remember start of DLC (see below).
206 self.ss_block = self.samplenum
208 # Bits 15-18: Data length code (DLC), in number of bytes (0-8).
210 self.dlc = int(''.join(str(d) for d in self.bits[15:18 + 1]), 2)
211 self.putb([10, ['Data length code: %d' % self.dlc,
212 'DLC: %d' % self.dlc, 'DLC']])
213 self.last_databit = 18 + (self.dlc * 8)
215 self.putb([16, ['Data length code (DLC) > 8 is not allowed']])
217 # Remember all databyte bits, except the very last one.
218 elif bitnum in range(19, self.last_databit):
219 self.ss_databytebits.append(self.samplenum)
221 # Bits 19-X: Data field (0-8 bytes, depending on DLC)
222 # The bits within a data byte are transferred MSB-first.
223 elif bitnum == self.last_databit:
224 self.ss_databytebits.append(self.samplenum) # Last databyte bit.
225 for i in range(self.dlc):
227 b = int(''.join(str(d) for d in self.bits[x:x + 8]), 2)
228 ss = self.ss_databytebits[i * 8]
229 es = self.ss_databytebits[((i + 1) * 8) - 1]
230 self.putg(ss, es, [0, ['Data byte %d: 0x%02x' % (i, b),
231 'DB %d: 0x%02x' % (i, b), 'DB']])
232 self.ss_databytebits = []
234 elif bitnum > self.last_databit:
235 return self.decode_frame_end(can_rx, bitnum)
239 # Returns True if the frame ended (EOF), False otherwise.
240 def decode_extended_frame(self, can_rx, bitnum):
242 # Remember start of EID (see below).
244 self.ss_block = self.samplenum
246 # Bits 14-31: Extended identifier (EID[17..0])
248 self.eid = int(''.join(str(d) for d in self.bits[14:]), 2)
249 s = '%d (0x%x)' % (self.eid, self.eid)
250 self.putb([4, ['Extended Identifier: %s' % s,
251 'Extended ID: %s' % s, 'Extended ID', 'EID']])
253 self.fullid = self.id << 18 | self.eid
254 s = '%d (0x%x)' % (self.fullid, self.fullid)
255 self.putb([5, ['Full Identifier: %s' % s, 'Full ID: %s' % s,
258 # Bit 12: Substitute remote request (SRR) bit
259 self.put12([9, ['Substitute remote request: %d' % self.bits[12],
260 'SRR: %d' % self.bits[12], 'SRR']])
262 # Bit 32: Remote transmission request (RTR) bit
263 # Data frame: dominant, remote frame: recessive
264 # Remote frames do not contain a data field.
266 rtr = 'remote' if can_rx == 1 else 'data'
267 self.putx([8, ['Remote transmission request: %s frame' % rtr,
268 'RTR: %s frame' % rtr, 'RTR']])
270 # Bit 33: RB1 (reserved bit)
272 self.putx([7, ['Reserved bit 1: %d' % can_rx,
273 'RB1: %d' % can_rx, 'RB1']])
275 # Bit 34: RB0 (reserved bit)
277 self.putx([7, ['Reserved bit 0: %d' % can_rx,
278 'RB0: %d' % can_rx, 'RB0']])
280 # Remember start of DLC (see below).
282 self.ss_block = self.samplenum
284 # Bits 35-38: Data length code (DLC), in number of bytes (0-8).
286 self.dlc = int(''.join(str(d) for d in self.bits[35:38 + 1]), 2)
287 self.putb([10, ['Data length code: %d' % self.dlc,
288 'DLC: %d' % self.dlc, 'DLC']])
289 self.last_databit = 38 + (self.dlc * 8)
291 # Remember all databyte bits, except the very last one.
292 elif bitnum in range(39, self.last_databit):
293 self.ss_databytebits.append(self.samplenum)
295 # Bits 39-X: Data field (0-8 bytes, depending on DLC)
296 # The bits within a data byte are transferred MSB-first.
297 elif bitnum == self.last_databit:
298 self.ss_databytebits.append(self.samplenum) # Last databyte bit.
299 for i in range(self.dlc):
301 b = int(''.join(str(d) for d in self.bits[x:x + 8]), 2)
302 ss = self.ss_databytebits[i * 8]
303 es = self.ss_databytebits[((i + 1) * 8) - 1]
304 self.putg(ss, es, [0, ['Data byte %d: 0x%02x' % (i, b),
305 'DB %d: 0x%02x' % (i, b), 'DB']])
306 self.ss_databytebits = []
308 elif bitnum > self.last_databit:
309 return self.decode_frame_end(can_rx, bitnum)
313 def handle_bit(self, can_rx):
314 self.rawbits.append(can_rx)
315 self.bits.append(can_rx)
317 # Get the index of the current CAN frame bit (without stuff bits).
318 bitnum = len(self.bits) - 1
320 # If this is a stuff bit, remove it from self.bits and ignore it.
321 if self.is_stuff_bit():
322 self.putx([15, [str(can_rx)]])
323 self.curbit += 1 # Increase self.curbit (bitnum is not affected).
326 self.putx([17, [str(can_rx)]])
328 # Bit 0: Start of frame (SOF) bit
330 self.putx([1, ['Start of frame', 'SOF', 'S']])
332 self.putx([16, ['Start of frame (SOF) must be a dominant bit']])
334 # Remember start of ID (see below).
336 self.ss_block = self.samplenum
338 # Bits 1-11: Identifier (ID[10..0])
339 # The bits ID[10..4] must NOT be all recessive.
341 self.id = int(''.join(str(d) for d in self.bits[1:]), 2)
342 s = '%d (0x%x)' % (self.id, self.id),
343 self.putb([3, ['Identifier: %s' % s, 'ID: %s' % s, 'ID']])
344 if (self.id & 0x7f0) == 0x7f0:
345 self.putb([16, ['Identifier bits 10..4 must not be all recessive']])
347 # RTR or SRR bit, depending on frame type (gets handled later).
349 # self.putx([0, ['RTR/SRR: %d' % can_rx]]) # Debug only.
350 self.ss_bit12 = self.samplenum
352 # Bit 13: Identifier extension (IDE) bit
353 # Standard frame: dominant, extended frame: recessive
355 ide = self.frame_type = 'standard' if can_rx == 0 else 'extended'
356 self.putx([6, ['Identifier extension bit: %s frame' % ide,
357 'IDE: %s frame' % ide, 'IDE']])
359 # Bits 14-X: Frame-type dependent, passed to the resp. handlers.
361 if self.frame_type == 'standard':
362 done = self.decode_standard_frame(can_rx, bitnum)
364 done = self.decode_extended_frame(can_rx, bitnum)
366 # The handlers return True if a frame ended (EOF).
370 # After a frame there are 3 intermission bits (recessive).
371 # After these bits, the bus is considered free.
376 if not self.samplerate:
377 raise SamplerateError('Cannot decode without samplerate.')
381 if self.state == 'IDLE':
382 # Wait for a dominant state (logic 0) on the bus.
383 (can_rx,) = self.wait({0: 'l'})
384 self.sof = self.samplenum
385 self.state = 'GET BITS'
386 elif self.state == 'GET BITS':
387 # Wait until we're in the correct bit/sampling position.
388 pos = self.get_sample_point(self.curbit)
389 (can_rx,) = self.wait({'skip': pos - self.samplenum})
390 self.handle_bit(can_rx)