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 last_6_bits = self.rawbits[-6:]
117 if last_6_bits not in ([0, 0, 0, 0, 0, 1], [1, 1, 1, 1, 1, 0]):
120 # Stuff bit. Keep it in self.rawbits, but drop it from self.bits.
121 self.bits.pop() # Drop last bit.
124 def is_valid_crc(self, crc_bits):
127 def decode_error_frame(self, bits):
130 def decode_overload_frame(self, bits):
133 # Both standard and extended frames end with CRC, CRC delimiter, ACK,
134 # ACK delimiter, and EOF fields. Handle them in a common function.
135 # Returns True if the frame ended (EOF), False otherwise.
136 def decode_frame_end(self, can_rx, bitnum):
138 # Remember start of CRC sequence (see below).
139 if bitnum == (self.last_databit + 1):
140 self.ss_block = self.samplenum
142 # CRC sequence (15 bits)
143 elif bitnum == (self.last_databit + 15):
144 x = self.last_databit + 1
145 crc_bits = self.bits[x:x + 15 + 1]
146 self.crc = int(''.join(str(d) for d in crc_bits), 2)
147 self.putb([11, ['CRC sequence: 0x%04x' % self.crc,
148 'CRC: 0x%04x' % self.crc, 'CRC']])
149 if not self.is_valid_crc(crc_bits):
150 self.putb([16, ['CRC is invalid']])
152 # CRC delimiter bit (recessive)
153 elif bitnum == (self.last_databit + 16):
154 self.putx([12, ['CRC delimiter: %d' % can_rx,
155 'CRC d: %d' % can_rx, 'CRC d']])
157 self.putx([16, ['CRC delimiter must be a recessive bit']])
159 # ACK slot bit (dominant: ACK, recessive: NACK)
160 elif bitnum == (self.last_databit + 17):
161 ack = 'ACK' if can_rx == 0 else 'NACK'
162 self.putx([13, ['ACK slot: %s' % ack, 'ACK s: %s' % ack, 'ACK s']])
164 # ACK delimiter bit (recessive)
165 elif bitnum == (self.last_databit + 18):
166 self.putx([14, ['ACK delimiter: %d' % can_rx,
167 'ACK d: %d' % can_rx, 'ACK d']])
169 self.putx([16, ['ACK delimiter must be a recessive bit']])
171 # Remember start of EOF (see below).
172 elif bitnum == (self.last_databit + 19):
173 self.ss_block = self.samplenum
175 # End of frame (EOF), 7 recessive bits
176 elif bitnum == (self.last_databit + 25):
177 self.putb([2, ['End of frame', 'EOF', 'E']])
178 if self.rawbits[-7:] != [1, 1, 1, 1, 1, 1, 1]:
179 self.putb([16, ['End of frame (EOF) must be 7 recessive bits']])
180 self.reset_variables()
185 # Returns True if the frame ended (EOF), False otherwise.
186 def decode_standard_frame(self, can_rx, bitnum):
188 # Bit 14: RB0 (reserved bit)
189 # Has to be sent dominant, but receivers should accept recessive too.
191 self.putx([7, ['Reserved bit 0: %d' % can_rx,
192 'RB0: %d' % can_rx, 'RB0']])
194 # Bit 12: Remote transmission request (RTR) bit
195 # Data frame: dominant, remote frame: recessive
196 # Remote frames do not contain a data field.
197 rtr = 'remote' if self.bits[12] == 1 else 'data'
198 self.put12([8, ['Remote transmission request: %s frame' % rtr,
199 'RTR: %s frame' % rtr, 'RTR']])
201 # Remember start of DLC (see below).
203 self.ss_block = self.samplenum
205 # Bits 15-18: Data length code (DLC), in number of bytes (0-8).
207 self.dlc = int(''.join(str(d) for d in self.bits[15:18 + 1]), 2)
208 self.putb([10, ['Data length code: %d' % self.dlc,
209 'DLC: %d' % self.dlc, 'DLC']])
210 self.last_databit = 18 + (self.dlc * 8)
212 self.putb([16, ['Data length code (DLC) > 8 is not allowed']])
214 # Remember all databyte bits, except the very last one.
215 elif bitnum in range(19, self.last_databit):
216 self.ss_databytebits.append(self.samplenum)
218 # Bits 19-X: Data field (0-8 bytes, depending on DLC)
219 # The bits within a data byte are transferred MSB-first.
220 elif bitnum == self.last_databit:
221 self.ss_databytebits.append(self.samplenum) # Last databyte bit.
222 for i in range(self.dlc):
224 b = int(''.join(str(d) for d in self.bits[x:x + 8]), 2)
225 ss = self.ss_databytebits[i * 8]
226 es = self.ss_databytebits[((i + 1) * 8) - 1]
227 self.putg(ss, es, [0, ['Data byte %d: 0x%02x' % (i, b),
228 'DB %d: 0x%02x' % (i, b), 'DB']])
229 self.ss_databytebits = []
231 elif bitnum > self.last_databit:
232 return self.decode_frame_end(can_rx, bitnum)
236 # Returns True if the frame ended (EOF), False otherwise.
237 def decode_extended_frame(self, can_rx, bitnum):
239 # Remember start of EID (see below).
241 self.ss_block = self.samplenum
243 # Bits 14-31: Extended identifier (EID[17..0])
245 self.eid = int(''.join(str(d) for d in self.bits[14:]), 2)
246 s = '%d (0x%x)' % (self.eid, self.eid)
247 self.putb([4, ['Extended Identifier: %s' % s,
248 'Extended ID: %s' % s, 'Extended ID', 'EID']])
250 self.fullid = self.id << 18 | self.eid
251 s = '%d (0x%x)' % (self.fullid, self.fullid)
252 self.putb([5, ['Full Identifier: %s' % s, 'Full ID: %s' % s,
255 # Bit 12: Substitute remote request (SRR) bit
256 self.put12([9, ['Substitute remote request: %d' % self.bits[12],
257 'SRR: %d' % self.bits[12], 'SRR']])
259 # Bit 32: Remote transmission request (RTR) bit
260 # Data frame: dominant, remote frame: recessive
261 # Remote frames do not contain a data field.
263 rtr = 'remote' if can_rx == 1 else 'data'
264 self.putx([8, ['Remote transmission request: %s frame' % rtr,
265 'RTR: %s frame' % rtr, 'RTR']])
267 # Bit 33: RB1 (reserved bit)
269 self.putx([7, ['Reserved bit 1: %d' % can_rx,
270 'RB1: %d' % can_rx, 'RB1']])
272 # Bit 34: RB0 (reserved bit)
274 self.putx([7, ['Reserved bit 0: %d' % can_rx,
275 'RB0: %d' % can_rx, 'RB0']])
277 # Remember start of DLC (see below).
279 self.ss_block = self.samplenum
281 # Bits 35-38: Data length code (DLC), in number of bytes (0-8).
283 self.dlc = int(''.join(str(d) for d in self.bits[35:38 + 1]), 2)
284 self.putb([10, ['Data length code: %d' % self.dlc,
285 'DLC: %d' % self.dlc, 'DLC']])
286 self.last_databit = 38 + (self.dlc * 8)
288 # Remember all databyte bits, except the very last one.
289 elif bitnum in range(39, self.last_databit):
290 self.ss_databytebits.append(self.samplenum)
292 # Bits 39-X: Data field (0-8 bytes, depending on DLC)
293 # The bits within a data byte are transferred MSB-first.
294 elif bitnum == self.last_databit:
295 self.ss_databytebits.append(self.samplenum) # Last databyte bit.
296 for i in range(self.dlc):
298 b = int(''.join(str(d) for d in self.bits[x:x + 8]), 2)
299 ss = self.ss_databytebits[i * 8]
300 es = self.ss_databytebits[((i + 1) * 8) - 1]
301 self.putg(ss, es, [0, ['Data byte %d: 0x%02x' % (i, b),
302 'DB %d: 0x%02x' % (i, b), 'DB']])
303 self.ss_databytebits = []
305 elif bitnum > self.last_databit:
306 return self.decode_frame_end(can_rx, bitnum)
310 def handle_bit(self, can_rx):
311 self.rawbits.append(can_rx)
312 self.bits.append(can_rx)
314 # Get the index of the current CAN frame bit (without stuff bits).
315 bitnum = len(self.bits) - 1
317 # If this is a stuff bit, remove it from self.bits and ignore it.
318 if self.is_stuff_bit():
319 self.putx([15, [str(can_rx)]])
320 self.curbit += 1 # Increase self.curbit (bitnum is not affected).
323 self.putx([17, [str(can_rx)]])
325 # Bit 0: Start of frame (SOF) bit
327 self.putx([1, ['Start of frame', 'SOF', 'S']])
329 self.putx([16, ['Start of frame (SOF) must be a dominant bit']])
331 # Remember start of ID (see below).
333 self.ss_block = self.samplenum
335 # Bits 1-11: Identifier (ID[10..0])
336 # The bits ID[10..4] must NOT be all recessive.
338 self.id = int(''.join(str(d) for d in self.bits[1:]), 2)
339 s = '%d (0x%x)' % (self.id, self.id),
340 self.putb([3, ['Identifier: %s' % s, 'ID: %s' % s, 'ID']])
341 if (self.id & 0x7f0) == 0x7f0:
342 self.putb([16, ['Identifier bits 10..4 must not be all recessive']])
344 # RTR or SRR bit, depending on frame type (gets handled later).
346 # self.putx([0, ['RTR/SRR: %d' % can_rx]]) # Debug only.
347 self.ss_bit12 = self.samplenum
349 # Bit 13: Identifier extension (IDE) bit
350 # Standard frame: dominant, extended frame: recessive
352 ide = self.frame_type = 'standard' if can_rx == 0 else 'extended'
353 self.putx([6, ['Identifier extension bit: %s frame' % ide,
354 'IDE: %s frame' % ide, 'IDE']])
356 # Bits 14-X: Frame-type dependent, passed to the resp. handlers.
358 if self.frame_type == 'standard':
359 done = self.decode_standard_frame(can_rx, bitnum)
361 done = self.decode_extended_frame(can_rx, bitnum)
363 # The handlers return True if a frame ended (EOF).
367 # After a frame there are 3 intermission bits (recessive).
368 # After these bits, the bus is considered free.
373 if not self.samplerate:
374 raise SamplerateError('Cannot decode without samplerate.')
378 if self.state == 'IDLE':
379 # Wait for a dominant state (logic 0) on the bus.
380 (can_rx,) = self.wait({0: 'l'})
381 self.sof = self.samplenum
382 self.state = 'GET BITS'
383 elif self.state == 'GET BITS':
384 # Wait until we're in the correct bit/sampling position.
385 pos = self.get_sample_point(self.curbit)
386 (can_rx,) = self.wait({'skip': pos - self.samplenum})
387 self.handle_bit(can_rx)