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, write to the Free Software
18 ## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
21 import sigrokdecode as srd
23 class SamplerateError(Exception):
26 class Decoder(srd.Decoder):
30 longname = 'Controller Area Network'
31 desc = 'Field bus protocol for distributed realtime control.'
36 {'id': 'can_rx', 'name': 'CAN RX', 'desc': 'CAN bus line'},
39 {'id': 'bitrate', 'desc': 'Bitrate (bits/s)', 'default': 1000000},
40 {'id': 'sample_point', 'desc': 'Sample point (%)', 'default': 70.0},
43 ('data', 'CAN payload data'),
44 ('sof', 'Start of frame'),
45 ('eof', 'End of frame'),
47 ('ext-id', 'Extended identifier'),
48 ('full-id', 'Full identifier'),
49 ('ide', 'Identifier extension bit'),
50 ('reserved-bit', 'Reserved bit 0 and 1'),
51 ('rtr', 'Remote transmission request'),
52 ('srr', 'Substitute remote request'),
53 ('dlc', 'Data length count'),
54 ('crc-sequence', 'CRC sequence'),
55 ('crc-delimiter', 'CRC delimiter'),
56 ('ack-slot', 'ACK slot'),
57 ('ack-delimiter', 'ACK delimiter'),
58 ('stuff-bit', 'Stuff bit'),
59 ('warnings', 'Human-readable warnings'),
63 ('bits', 'Bits', (17,)),
64 ('fields', 'Fields', tuple(range(17))),
67 def __init__(self, **kwargs):
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 # Return True if we reached the desired bit position, False otherwise.
109 def reached_bit(self, bitnum):
110 bitpos = int(self.sof + (self.bit_width * bitnum) + self.bitpos)
111 if self.samplenum >= bitpos:
115 def is_stuff_bit(self):
116 # CAN uses NRZ encoding and bit stuffing.
117 # After 5 identical bits, a stuff bit of opposite value is added.
118 last_6_bits = self.rawbits[-6:]
119 if last_6_bits not in ([0, 0, 0, 0, 0, 1], [1, 1, 1, 1, 1, 0]):
122 # Stuff bit. Keep it in self.rawbits, but drop it from self.bits.
123 self.putx([15, ['Stuff bit: %d' % self.rawbits[-1],
124 'SB: %d' % self.rawbits[-1], 'SB']])
125 self.bits.pop() # Drop last bit.
128 def is_valid_crc(self, crc_bits):
131 def decode_error_frame(self, bits):
134 def decode_overload_frame(self, bits):
137 # Both standard and extended frames end with CRC, CRC delimiter, ACK,
138 # ACK delimiter, and EOF fields. Handle them in a common function.
139 # Returns True if the frame ended (EOF), False otherwise.
140 def decode_frame_end(self, can_rx, bitnum):
142 # Remember start of CRC sequence (see below).
143 if bitnum == (self.last_databit + 1):
144 self.ss_block = self.samplenum
146 # CRC sequence (15 bits)
147 elif bitnum == (self.last_databit + 15):
148 x = self.last_databit + 1
149 crc_bits = self.bits[x:x + 15 + 1]
150 self.crc = int(''.join(str(d) for d in crc_bits), 2)
151 self.putb([11, ['CRC sequence: 0x%04x' % self.crc,
152 'CRC: 0x%04x' % self.crc, 'CRC']])
153 if not self.is_valid_crc(crc_bits):
154 self.putb([16, ['CRC is invalid']])
156 # CRC delimiter bit (recessive)
157 elif bitnum == (self.last_databit + 16):
158 self.putx([12, ['CRC delimiter: %d' % can_rx,
159 'CRC d: %d' % can_rx, 'CRC d']])
161 # ACK slot bit (dominant: ACK, recessive: NACK)
162 elif bitnum == (self.last_databit + 17):
163 ack = 'ACK' if can_rx == 0 else 'NACK'
164 self.putx([13, ['ACK slot: %s' % ack, 'ACK s: %s' % ack, 'ACK s']])
166 # ACK delimiter bit (recessive)
167 elif bitnum == (self.last_databit + 18):
168 self.putx([14, ['ACK delimiter: %d' % can_rx,
169 'ACK d: %d' % can_rx, 'ACK d']])
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 self.reset_variables()
183 # Returns True if the frame ended (EOF), False otherwise.
184 def decode_standard_frame(self, can_rx, bitnum):
186 # Bit 14: RB0 (reserved bit)
187 # Has to be sent dominant, but receivers should accept recessive too.
189 self.putx([7, ['Reserved bit 0: %d' % can_rx,
190 'RB0: %d' % can_rx, 'RB0']])
192 # Bit 12: Remote transmission request (RTR) bit
193 # Data frame: dominant, remote frame: recessive
194 # Remote frames do not contain a data field.
195 rtr = 'remote' if self.bits[12] == 1 else 'data'
196 self.put12([8, ['Remote transmission request: %s frame' % rtr,
197 'RTR: %s frame' % rtr, 'RTR']])
199 # Remember start of DLC (see below).
201 self.ss_block = self.samplenum
203 # Bits 15-18: Data length code (DLC), in number of bytes (0-8).
205 self.dlc = int(''.join(str(d) for d in self.bits[15:18 + 1]), 2)
206 self.putb([10, ['Data length code: %d' % self.dlc,
207 'DLC: %d' % self.dlc, 'DLC']])
208 self.last_databit = 18 + (self.dlc * 8)
210 # Remember all databyte bits, except the very last one.
211 elif bitnum in range(19, self.last_databit):
212 self.ss_databytebits.append(self.samplenum)
214 # Bits 19-X: Data field (0-8 bytes, depending on DLC)
215 # The bits within a data byte are transferred MSB-first.
216 elif bitnum == self.last_databit:
217 self.ss_databytebits.append(self.samplenum) # Last databyte bit.
218 for i in range(self.dlc):
220 b = int(''.join(str(d) for d in self.bits[x:x + 8]), 2)
221 ss = self.ss_databytebits[i * 8]
222 es = self.ss_databytebits[((i + 1) * 8) - 1]
223 self.putg(ss, es, [0, ['Data byte %d: 0x%02x' % (i, b),
224 'DB %d: 0x%02x' % (i, b), 'DB']])
225 self.ss_databytebits = []
227 elif bitnum > self.last_databit:
228 return self.decode_frame_end(can_rx, bitnum)
232 # Returns True if the frame ended (EOF), False otherwise.
233 def decode_extended_frame(self, can_rx, bitnum):
235 # Remember start of EID (see below).
237 self.ss_block = self.samplenum
239 # Bits 14-31: Extended identifier (EID[17..0])
241 self.eid = int(''.join(str(d) for d in self.bits[14:]), 2)
242 s = '%d (0x%x)' % (self.eid, self.eid)
243 self.putb([4, ['Extended Identifier: %s' % s,
244 'Extended ID: %s' % s, 'Extended ID', 'EID']])
246 self.fullid = self.id << 18 | self.eid
247 s = '%d (0x%x)' % (self.fullid, self.fullid)
248 self.putb([5, ['Full Identifier: %s' % s, 'Full ID: %s' % s,
251 # Bit 12: Substitute remote request (SRR) bit
252 self.put12([9, ['Substitute remote request: %d' % self.bits[12],
253 'SRR: %d' % self.bits[12], 'SRR']])
255 # Bit 32: Remote transmission request (RTR) bit
256 # Data frame: dominant, remote frame: recessive
257 # Remote frames do not contain a data field.
259 rtr = 'remote' if can_rx == 1 else 'data'
260 self.putx([8, ['Remote transmission request: %s frame' % rtr,
261 'RTR: %s frame' % rtr, 'RTR']])
263 # Bit 33: RB1 (reserved bit)
265 self.putx([7, ['Reserved bit 1: %d' % can_rx,
266 'RB1: %d' % can_rx, 'RB1']])
268 # Bit 34: RB0 (reserved bit)
270 self.putx([7, ['Reserved bit 0: %d' % can_rx,
271 'RB0: %d' % can_rx, 'RB0']])
273 # Remember start of DLC (see below).
275 self.ss_block = self.samplenum
277 # Bits 35-38: Data length code (DLC), in number of bytes (0-8).
279 self.dlc = int(''.join(str(d) for d in self.bits[35:38 + 1]), 2)
280 self.putb([10, ['Data length code: %d' % self.dlc,
281 'DLC: %d' % self.dlc, 'DLC']])
282 self.last_databit = 38 + (self.dlc * 8)
284 # Remember all databyte bits, except the very last one.
285 elif bitnum in range(39, self.last_databit):
286 self.ss_databytebits.append(self.samplenum)
288 # Bits 39-X: Data field (0-8 bytes, depending on DLC)
289 # The bits within a data byte are transferred MSB-first.
290 elif bitnum == self.last_databit:
291 self.ss_databytebits.append(self.samplenum) # Last databyte bit.
292 for i in range(self.dlc):
294 b = int(''.join(str(d) for d in self.bits[x:x + 8]), 2)
295 ss = self.ss_databytebits[i * 8]
296 es = self.ss_databytebits[((i + 1) * 8) - 1]
297 self.putg(ss, es, [0, ['Data byte %d: 0x%02x' % (i, b),
298 'DB %d: 0x%02x' % (i, b), 'DB']])
299 self.ss_databytebits = []
301 elif bitnum > self.last_databit:
302 return self.decode_frame_end(can_rx, bitnum)
306 def handle_bit(self, can_rx):
307 self.rawbits.append(can_rx)
308 self.bits.append(can_rx)
310 # Get the index of the current CAN frame bit (without stuff bits).
311 bitnum = len(self.bits) - 1
313 # Emit a bit value annotation.
314 self.putx([17, [str(can_rx)]])
316 # If this is a stuff bit, remove it from self.bits and ignore it.
317 if self.is_stuff_bit():
318 self.curbit += 1 # Increase self.curbit (bitnum is not affected).
321 # Bit 0: Start of frame (SOF) bit
324 self.putx([1, ['Start of frame', 'SOF', 'S']])
326 self.putx([16, ['Start of frame (SOF) must be a dominant bit']])
328 # Remember start of ID (see below).
330 self.ss_block = self.samplenum
332 # Bits 1-11: Identifier (ID[10..0])
333 # The bits ID[10..4] must NOT be all recessive.
335 self.id = int(''.join(str(d) for d in self.bits[1:]), 2)
336 s = '%d (0x%x)' % (self.id, self.id),
337 self.putb([3, ['Identifier: %s' % s, 'ID: %s' % s, 'ID']])
339 # RTR or SRR bit, depending on frame type (gets handled later).
341 # self.putx([0, ['RTR/SRR: %d' % can_rx]]) # Debug only.
342 self.ss_bit12 = self.samplenum
344 # Bit 13: Identifier extension (IDE) bit
345 # Standard frame: dominant, extended frame: recessive
347 ide = self.frame_type = 'standard' if can_rx == 0 else 'extended'
348 self.putx([6, ['Identifier extension bit: %s frame' % ide,
349 'IDE: %s frame' % ide, 'IDE']])
351 # Bits 14-X: Frame-type dependent, passed to the resp. handlers.
353 if self.frame_type == 'standard':
354 done = self.decode_standard_frame(can_rx, bitnum)
356 done = self.decode_extended_frame(can_rx, bitnum)
358 # The handlers return True if a frame ended (EOF).
362 # After a frame there are 3 intermission bits (recessive).
363 # After these bits, the bus is considered free.
367 def decode(self, ss, es, data):
368 if not self.samplerate:
369 raise SamplerateError('Cannot decode without samplerate.')
370 for (self.samplenum, pins) in data:
375 if self.state == 'IDLE':
376 # Wait for a dominant state (logic 0) on the bus.
379 self.sof = self.samplenum
380 self.state = 'GET BITS'
381 elif self.state == 'GET BITS':
382 # Wait until we're in the correct bit/sampling position.
383 if not self.reached_bit(self.curbit):
385 self.handle_bit(can_rx)