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 # CAN protocol decoder
23 import sigrokdecode as srd
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'},
39 'bitrate': ['Bitrate', 1000000], # 1Mbit/s
40 'sample_point': ['Sample point', 70], # 70%
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'],
62 def __init__(self, **kwargs):
63 self.samplerate = None
64 self.reset_variables()
67 # self.out_proto = self.register(srd.OUTPUT_PYTHON)
68 self.out_ann = self.register(srd.OUTPUT_ANN)
70 def metadata(self, key, value):
71 if key == srd.SRD_CONF_SAMPLERATE:
72 self.samplerate = value
73 self.bit_width = float(self.samplerate) / float(self.options['bitrate'])
74 self.bitpos = (self.bit_width / 100.0) * self.options['sample_point']
76 # Generic helper for CAN bit annotations.
77 def putg(self, ss, es, data):
78 left, right = int(self.bitpos), int(self.bit_width - self.bitpos)
79 self.put(ss - left, es + right, self.out_ann, data)
81 # Single-CAN-bit annotation using the current samplenum.
83 self.putg(self.samplenum, self.samplenum, data)
85 # Single-CAN-bit annotation using the samplenum of CAN bit 12.
86 def put12(self, data):
87 self.putg(self.ss_bit12, self.ss_bit12, data)
89 # Multi-CAN-bit annotation from self.ss_block to current samplenum.
91 self.putg(self.ss_block, self.samplenum, data)
93 def reset_variables(self):
95 self.sof = self.frame_type = self.dlc = None
96 self.rawbits = [] # All bits, including stuff bits
97 self.bits = [] # Only actual CAN frame bits (no stuff bits)
98 self.curbit = 0 # Current bit of CAN frame (bit 0 == SOF)
99 self.last_databit = 999 # Positive value that bitnum+x will never match
102 self.ss_databytebits = []
104 # Return True if we reached the desired bit position, False otherwise.
105 def reached_bit(self, bitnum):
106 bitpos = int(self.sof + (self.bit_width * bitnum) + self.bitpos)
107 if self.samplenum >= bitpos:
111 def is_stuff_bit(self):
112 # CAN uses NRZ encoding and bit stuffing.
113 # After 5 identical bits, a stuff bit of opposite value is added.
114 last_6_bits = self.rawbits[-6:]
115 if last_6_bits not in ([0, 0, 0, 0, 0, 1], [1, 1, 1, 1, 1, 0]):
118 # Stuff bit. Keep it in self.rawbits, but drop it from self.bits.
119 self.putx([15, ['Stuff bit: %d' % self.rawbits[-1],
120 'SB: %d' % self.rawbits[-1], 'SB']])
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 # ACK slot bit (dominant: ACK, recessive: NACK)
158 elif bitnum == (self.last_databit + 17):
159 ack = 'ACK' if can_rx == 0 else 'NACK'
160 self.putx([13, ['ACK slot: %s' % ack, 'ACK s: %s' % ack, 'ACK s']])
162 # ACK delimiter bit (recessive)
163 elif bitnum == (self.last_databit + 18):
164 self.putx([14, ['ACK delimiter: %d' % can_rx,
165 'ACK d: %d' % can_rx, 'ACK d']])
167 # Remember start of EOF (see below).
168 elif bitnum == (self.last_databit + 19):
169 self.ss_block = self.samplenum
171 # End of frame (EOF), 7 recessive bits
172 elif bitnum == (self.last_databit + 25):
173 self.putb([2, ['End of frame', 'EOF', 'E']])
174 self.reset_variables()
179 # Returns True if the frame ended (EOF), False otherwise.
180 def decode_standard_frame(self, can_rx, bitnum):
182 # Bit 14: RB0 (reserved bit)
183 # Has to be sent dominant, but receivers should accept recessive too.
185 self.putx([7, ['Reserved bit 0: %d' % can_rx,
186 'RB0: %d' % can_rx, 'RB0']])
188 # Bit 12: Remote transmission request (RTR) bit
189 # Data frame: dominant, remote frame: recessive
190 # Remote frames do not contain a data field.
191 rtr = 'remote' if self.bits[12] == 1 else 'data'
192 self.put12([8, ['Remote transmission request: %s frame' % rtr,
193 'RTR: %s frame' % rtr, 'RTR']])
195 # Remember start of DLC (see below).
197 self.ss_block = self.samplenum
199 # Bits 15-18: Data length code (DLC), in number of bytes (0-8).
201 self.dlc = int(''.join(str(d) for d in self.bits[15:18 + 1]), 2)
202 self.putb([10, ['Data length code: %d' % self.dlc,
203 'DLC: %d' % self.dlc, 'DLC']])
204 self.last_databit = 18 + (self.dlc * 8)
206 # Remember all databyte bits, except the very last one.
207 elif bitnum in range(19, self.last_databit):
208 self.ss_databytebits.append(self.samplenum)
210 # Bits 19-X: Data field (0-8 bytes, depending on DLC)
211 # The bits within a data byte are transferred MSB-first.
212 elif bitnum == self.last_databit:
213 self.ss_databytebits.append(self.samplenum) # Last databyte bit.
214 for i in range(self.dlc):
216 b = int(''.join(str(d) for d in self.bits[x:x + 8]), 2)
217 ss = self.ss_databytebits[i * 8]
218 es = self.ss_databytebits[((i + 1) * 8) - 1]
219 self.putg(ss, es, [0, ['Data byte %d: 0x%02x' % (i, b),
220 'DB %d: 0x%02x' % (i, b), 'DB']])
221 self.ss_databytebits = []
223 elif bitnum > self.last_databit:
224 return self.decode_frame_end(can_rx, bitnum)
228 # Returns True if the frame ended (EOF), False otherwise.
229 def decode_extended_frame(self, can_rx, bitnum):
231 # Remember start of EID (see below).
233 self.ss_block = self.samplenum
235 # Bits 14-31: Extended identifier (EID[17..0])
237 self.eid = int(''.join(str(d) for d in self.bits[14:]), 2)
238 s = '%d (0x%x)' % (self.eid, self.eid)
239 self.putb([4, ['Extended Identifier: %s' % s,
240 'Extended ID: %s' % s, 'Extended ID', 'EID']])
242 self.fullid = self.id << 18 | self.eid
243 s = '%d (0x%x)' % (self.fullid, self.fullid)
244 self.putb([5, ['Full Identifier: %s' % s, 'Full ID: %s' % s,
247 # Bit 12: Substitute remote request (SRR) bit
248 self.put12([9, ['Substitute remote request: %d' % self.bits[12],
249 'SRR: %d' % self.bits[12], 'SRR']])
251 # Bit 32: Remote transmission request (RTR) bit
252 # Data frame: dominant, remote frame: recessive
253 # Remote frames do not contain a data field.
255 rtr = 'remote' if can_rx == 1 else 'data'
256 self.putx([8, ['Remote transmission request: %s frame' % rtr,
257 'RTR: %s frame' % rtr, 'RTR']])
259 # Bit 33: RB1 (reserved bit)
261 self.putx([7, ['Reserved bit 1: %d' % can_rx,
262 'RB1: %d' % can_rx, 'RB1']])
264 # Bit 34: RB0 (reserved bit)
266 self.putx([7, ['Reserved bit 0: %d' % can_rx,
267 'RB0: %d' % can_rx, 'RB0']])
269 # Remember start of DLC (see below).
271 self.ss_block = self.samplenum
273 # Bits 35-38: Data length code (DLC), in number of bytes (0-8).
275 self.dlc = int(''.join(str(d) for d in self.bits[35:38 + 1]), 2)
276 self.putb([10, ['Data length code: %d' % self.dlc,
277 'DLC: %d' % self.dlc, 'DLC']])
278 self.last_databit = 38 + (self.dlc * 8)
280 # Remember all databyte bits, except the very last one.
281 elif bitnum in range(39, self.last_databit):
282 self.ss_databytebits.append(self.samplenum)
284 # Bits 39-X: Data field (0-8 bytes, depending on DLC)
285 # The bits within a data byte are transferred MSB-first.
286 elif bitnum == self.last_databit:
287 self.ss_databytebits.append(self.samplenum) # Last databyte bit.
288 for i in range(self.dlc):
290 b = int(''.join(str(d) for d in self.bits[x:x + 8]), 2)
291 ss = self.ss_databytebits[i * 8]
292 es = self.ss_databytebits[((i + 1) * 8) - 1]
293 self.putg(ss, es, [0, ['Data byte %d: 0x%02x' % (i, b),
294 'DB %d: 0x%02x' % (i, b), 'DB']])
295 self.ss_databytebits = []
297 elif bitnum > self.last_databit:
298 return self.decode_frame_end(can_rx, bitnum)
302 def handle_bit(self, can_rx):
303 self.rawbits.append(can_rx)
304 self.bits.append(can_rx)
306 # Get the index of the current CAN frame bit (without stuff bits).
307 bitnum = len(self.bits) - 1
310 # self.putx([0, ['Bit %d (CAN bit %d): %d' % \
311 # (self.curbit, bitnum, can_rx)]])
313 # If this is a stuff bit, remove it from self.bits and ignore it.
314 if self.is_stuff_bit():
315 self.curbit += 1 # Increase self.curbit (bitnum is not affected).
318 # Bit 0: Start of frame (SOF) bit
321 self.putx([1, ['Start of frame', 'SOF', 'S']])
323 self.putx([16, ['Start of frame (SOF) must be a dominant bit']])
325 # Remember start of ID (see below).
327 self.ss_block = self.samplenum
329 # Bits 1-11: Identifier (ID[10..0])
330 # The bits ID[10..4] must NOT be all recessive.
332 self.id = int(''.join(str(d) for d in self.bits[1:]), 2)
333 s = '%d (0x%x)' % (self.id, self.id),
334 self.putb([3, ['Identifier: %s' % s, 'ID: %s' % s, 'ID']])
336 # RTR or SRR bit, depending on frame type (gets handled later).
338 # self.putx([0, ['RTR/SRR: %d' % can_rx]]) # Debug only.
339 self.ss_bit12 = self.samplenum
341 # Bit 13: Identifier extension (IDE) bit
342 # Standard frame: dominant, extended frame: recessive
344 ide = self.frame_type = 'standard' if can_rx == 0 else 'extended'
345 self.putx([6, ['Identifier extension bit: %s frame' % ide,
346 'IDE: %s frame' % ide, 'IDE']])
348 # Bits 14-X: Frame-type dependent, passed to the resp. handlers.
350 if self.frame_type == 'standard':
351 done = self.decode_standard_frame(can_rx, bitnum)
353 done = self.decode_extended_frame(can_rx, bitnum)
355 # The handlers return True if a frame ended (EOF).
359 # After a frame there are 3 intermission bits (recessive).
360 # After these bits, the bus is considered free.
364 def decode(self, ss, es, data):
365 if self.samplerate is None:
366 raise Exception("Cannot decode without samplerate.")
367 for (self.samplenum, pins) in data:
372 if self.state == 'IDLE':
373 # Wait for a dominant state (logic 0) on the bus.
376 self.sof = self.samplenum
377 self.state = 'GET BITS'
378 elif self.state == 'GET BITS':
379 # Wait until we're in the correct bit/sampling position.
380 if not self.reached_bit(self.curbit):
382 self.handle_bit(can_rx)
384 raise Exception("Invalid state: %s" % self.state)