## ## This file is part of the libsigrokdecode project. ## ## Copyright (C) 2012-2013 Uwe Hermann ## ## This program is free software; you can redistribute it and/or modify ## it under the terms of the GNU General Public License as published by ## the Free Software Foundation; either version 2 of the License, or ## (at your option) any later version. ## ## This program is distributed in the hope that it will be useful, ## but WITHOUT ANY WARRANTY; without even the implied warranty of ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ## GNU General Public License for more details. ## ## You should have received a copy of the GNU General Public License ## along with this program; if not, write to the Free Software ## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA ## import sigrokdecode as srd class Decoder(srd.Decoder): api_version = 1 id = 'can' name = 'CAN' longname = 'Controller Area Network' desc = 'Field bus protocol for distributed realtime control.' license = 'gplv2+' inputs = ['logic'] outputs = ['can'] probes = ( {'id': 'can_rx', 'name': 'CAN RX', 'desc': 'CAN bus line'}, ) options = ( {'id': 'bitrate', 'desc': 'Bitrate', 'default': 1000000}, # 1Mbit/s {'id': 'sample_point', 'desc': 'Sample point', 'default': 70.0}, # 70% ) annotations = ( ('data', 'CAN payload data'), ('sof', 'Start of frame'), ('eof', 'End of frame'), ('id', 'Identifier'), ('ext-id', 'Extended identifier'), ('full-id', 'Full identifier'), ('ide', 'Identifier extension bit'), ('reserved-bit', 'Reserved bit 0 and 1'), ('rtr', 'Remote transmission request'), ('srr', 'Substitute remote request'), ('dlc', 'Data length count'), ('crc-sequence', 'CRC sequence'), ('crc-delimiter', 'CRC delimiter'), ('ack-slot', 'ACK slot'), ('ack-delimiter', 'ACK delimiter'), ('stuff-bit', 'Stuff bit'), ('warnings', 'Human-readable warnings'), ) def __init__(self, **kwargs): self.samplerate = None self.reset_variables() def start(self): # self.out_python = self.register(srd.OUTPUT_PYTHON) self.out_ann = self.register(srd.OUTPUT_ANN) def metadata(self, key, value): if key == srd.SRD_CONF_SAMPLERATE: self.samplerate = value self.bit_width = float(self.samplerate) / float(self.options['bitrate']) self.bitpos = (self.bit_width / 100.0) * self.options['sample_point'] # Generic helper for CAN bit annotations. def putg(self, ss, es, data): left, right = int(self.bitpos), int(self.bit_width - self.bitpos) self.put(ss - left, es + right, self.out_ann, data) # Single-CAN-bit annotation using the current samplenum. def putx(self, data): self.putg(self.samplenum, self.samplenum, data) # Single-CAN-bit annotation using the samplenum of CAN bit 12. def put12(self, data): self.putg(self.ss_bit12, self.ss_bit12, data) # Multi-CAN-bit annotation from self.ss_block to current samplenum. def putb(self, data): self.putg(self.ss_block, self.samplenum, data) def reset_variables(self): self.state = 'IDLE' self.sof = self.frame_type = self.dlc = None self.rawbits = [] # All bits, including stuff bits self.bits = [] # Only actual CAN frame bits (no stuff bits) self.curbit = 0 # Current bit of CAN frame (bit 0 == SOF) self.last_databit = 999 # Positive value that bitnum+x will never match self.ss_block = None self.ss_bit12 = None self.ss_databytebits = [] # Return True if we reached the desired bit position, False otherwise. def reached_bit(self, bitnum): bitpos = int(self.sof + (self.bit_width * bitnum) + self.bitpos) if self.samplenum >= bitpos: return True return False def is_stuff_bit(self): # CAN uses NRZ encoding and bit stuffing. # After 5 identical bits, a stuff bit of opposite value is added. last_6_bits = self.rawbits[-6:] if last_6_bits not in ([0, 0, 0, 0, 0, 1], [1, 1, 1, 1, 1, 0]): return False # Stuff bit. Keep it in self.rawbits, but drop it from self.bits. self.putx([15, ['Stuff bit: %d' % self.rawbits[-1], 'SB: %d' % self.rawbits[-1], 'SB']]) self.bits.pop() # Drop last bit. return True def is_valid_crc(self, crc_bits): return True # TODO def decode_error_frame(self, bits): pass # TODO def decode_overload_frame(self, bits): pass # TODO # Both standard and extended frames end with CRC, CRC delimiter, ACK, # ACK delimiter, and EOF fields. Handle them in a common function. # Returns True if the frame ended (EOF), False otherwise. def decode_frame_end(self, can_rx, bitnum): # Remember start of CRC sequence (see below). if bitnum == (self.last_databit + 1): self.ss_block = self.samplenum # CRC sequence (15 bits) elif bitnum == (self.last_databit + 15): x = self.last_databit + 1 crc_bits = self.bits[x:x + 15 + 1] self.crc = int(''.join(str(d) for d in crc_bits), 2) self.putb([11, ['CRC sequence: 0x%04x' % self.crc, 'CRC: 0x%04x' % self.crc, 'CRC']]) if not self.is_valid_crc(crc_bits): self.putb([16, ['CRC is invalid']]) # CRC delimiter bit (recessive) elif bitnum == (self.last_databit + 16): self.putx([12, ['CRC delimiter: %d' % can_rx, 'CRC d: %d' % can_rx, 'CRC d']]) # ACK slot bit (dominant: ACK, recessive: NACK) elif bitnum == (self.last_databit + 17): ack = 'ACK' if can_rx == 0 else 'NACK' self.putx([13, ['ACK slot: %s' % ack, 'ACK s: %s' % ack, 'ACK s']]) # ACK delimiter bit (recessive) elif bitnum == (self.last_databit + 18): self.putx([14, ['ACK delimiter: %d' % can_rx, 'ACK d: %d' % can_rx, 'ACK d']]) # Remember start of EOF (see below). elif bitnum == (self.last_databit + 19): self.ss_block = self.samplenum # End of frame (EOF), 7 recessive bits elif bitnum == (self.last_databit + 25): self.putb([2, ['End of frame', 'EOF', 'E']]) self.reset_variables() return True return False # Returns True if the frame ended (EOF), False otherwise. def decode_standard_frame(self, can_rx, bitnum): # Bit 14: RB0 (reserved bit) # Has to be sent dominant, but receivers should accept recessive too. if bitnum == 14: self.putx([7, ['Reserved bit 0: %d' % can_rx, 'RB0: %d' % can_rx, 'RB0']]) # Bit 12: Remote transmission request (RTR) bit # Data frame: dominant, remote frame: recessive # Remote frames do not contain a data field. rtr = 'remote' if self.bits[12] == 1 else 'data' self.put12([8, ['Remote transmission request: %s frame' % rtr, 'RTR: %s frame' % rtr, 'RTR']]) # Remember start of DLC (see below). elif bitnum == 15: self.ss_block = self.samplenum # Bits 15-18: Data length code (DLC), in number of bytes (0-8). elif bitnum == 18: self.dlc = int(''.join(str(d) for d in self.bits[15:18 + 1]), 2) self.putb([10, ['Data length code: %d' % self.dlc, 'DLC: %d' % self.dlc, 'DLC']]) self.last_databit = 18 + (self.dlc * 8) # Remember all databyte bits, except the very last one. elif bitnum in range(19, self.last_databit): self.ss_databytebits.append(self.samplenum) # Bits 19-X: Data field (0-8 bytes, depending on DLC) # The bits within a data byte are transferred MSB-first. elif bitnum == self.last_databit: self.ss_databytebits.append(self.samplenum) # Last databyte bit. for i in range(self.dlc): x = 18 + (8 * i) + 1 b = int(''.join(str(d) for d in self.bits[x:x + 8]), 2) ss = self.ss_databytebits[i * 8] es = self.ss_databytebits[((i + 1) * 8) - 1] self.putg(ss, es, [0, ['Data byte %d: 0x%02x' % (i, b), 'DB %d: 0x%02x' % (i, b), 'DB']]) self.ss_databytebits = [] elif bitnum > self.last_databit: return self.decode_frame_end(can_rx, bitnum) return False # Returns True if the frame ended (EOF), False otherwise. def decode_extended_frame(self, can_rx, bitnum): # Remember start of EID (see below). if bitnum == 14: self.ss_block = self.samplenum # Bits 14-31: Extended identifier (EID[17..0]) elif bitnum == 31: self.eid = int(''.join(str(d) for d in self.bits[14:]), 2) s = '%d (0x%x)' % (self.eid, self.eid) self.putb([4, ['Extended Identifier: %s' % s, 'Extended ID: %s' % s, 'Extended ID', 'EID']]) self.fullid = self.id << 18 | self.eid s = '%d (0x%x)' % (self.fullid, self.fullid) self.putb([5, ['Full Identifier: %s' % s, 'Full ID: %s' % s, 'Full ID', 'FID']]) # Bit 12: Substitute remote request (SRR) bit self.put12([9, ['Substitute remote request: %d' % self.bits[12], 'SRR: %d' % self.bits[12], 'SRR']]) # Bit 32: Remote transmission request (RTR) bit # Data frame: dominant, remote frame: recessive # Remote frames do not contain a data field. if bitnum == 32: rtr = 'remote' if can_rx == 1 else 'data' self.putx([8, ['Remote transmission request: %s frame' % rtr, 'RTR: %s frame' % rtr, 'RTR']]) # Bit 33: RB1 (reserved bit) elif bitnum == 33: self.putx([7, ['Reserved bit 1: %d' % can_rx, 'RB1: %d' % can_rx, 'RB1']]) # Bit 34: RB0 (reserved bit) elif bitnum == 34: self.putx([7, ['Reserved bit 0: %d' % can_rx, 'RB0: %d' % can_rx, 'RB0']]) # Remember start of DLC (see below). elif bitnum == 35: self.ss_block = self.samplenum # Bits 35-38: Data length code (DLC), in number of bytes (0-8). elif bitnum == 38: self.dlc = int(''.join(str(d) for d in self.bits[35:38 + 1]), 2) self.putb([10, ['Data length code: %d' % self.dlc, 'DLC: %d' % self.dlc, 'DLC']]) self.last_databit = 38 + (self.dlc * 8) # Remember all databyte bits, except the very last one. elif bitnum in range(39, self.last_databit): self.ss_databytebits.append(self.samplenum) # Bits 39-X: Data field (0-8 bytes, depending on DLC) # The bits within a data byte are transferred MSB-first. elif bitnum == self.last_databit: self.ss_databytebits.append(self.samplenum) # Last databyte bit. for i in range(self.dlc): x = 38 + (8 * i) + 1 b = int(''.join(str(d) for d in self.bits[x:x + 8]), 2) ss = self.ss_databytebits[i * 8] es = self.ss_databytebits[((i + 1) * 8) - 1] self.putg(ss, es, [0, ['Data byte %d: 0x%02x' % (i, b), 'DB %d: 0x%02x' % (i, b), 'DB']]) self.ss_databytebits = [] elif bitnum > self.last_databit: return self.decode_frame_end(can_rx, bitnum) return False def handle_bit(self, can_rx): self.rawbits.append(can_rx) self.bits.append(can_rx) # Get the index of the current CAN frame bit (without stuff bits). bitnum = len(self.bits) - 1 # For debugging. # self.putx([0, ['Bit %d (CAN bit %d): %d' % \ # (self.curbit, bitnum, can_rx)]]) # If this is a stuff bit, remove it from self.bits and ignore it. if self.is_stuff_bit(): self.curbit += 1 # Increase self.curbit (bitnum is not affected). return # Bit 0: Start of frame (SOF) bit if bitnum == 0: if can_rx == 0: self.putx([1, ['Start of frame', 'SOF', 'S']]) else: self.putx([16, ['Start of frame (SOF) must be a dominant bit']]) # Remember start of ID (see below). elif bitnum == 1: self.ss_block = self.samplenum # Bits 1-11: Identifier (ID[10..0]) # The bits ID[10..4] must NOT be all recessive. elif bitnum == 11: self.id = int(''.join(str(d) for d in self.bits[1:]), 2) s = '%d (0x%x)' % (self.id, self.id), self.putb([3, ['Identifier: %s' % s, 'ID: %s' % s, 'ID']]) # RTR or SRR bit, depending on frame type (gets handled later). elif bitnum == 12: # self.putx([0, ['RTR/SRR: %d' % can_rx]]) # Debug only. self.ss_bit12 = self.samplenum # Bit 13: Identifier extension (IDE) bit # Standard frame: dominant, extended frame: recessive elif bitnum == 13: ide = self.frame_type = 'standard' if can_rx == 0 else 'extended' self.putx([6, ['Identifier extension bit: %s frame' % ide, 'IDE: %s frame' % ide, 'IDE']]) # Bits 14-X: Frame-type dependent, passed to the resp. handlers. elif bitnum >= 14: if self.frame_type == 'standard': done = self.decode_standard_frame(can_rx, bitnum) else: done = self.decode_extended_frame(can_rx, bitnum) # The handlers return True if a frame ended (EOF). if done: return # After a frame there are 3 intermission bits (recessive). # After these bits, the bus is considered free. self.curbit += 1 def decode(self, ss, es, data): if self.samplerate is None: raise Exception("Cannot decode without samplerate.") for (self.samplenum, pins) in data: (can_rx,) = pins # State machine. if self.state == 'IDLE': # Wait for a dominant state (logic 0) on the bus. if can_rx == 1: continue self.sof = self.samplenum self.state = 'GET BITS' elif self.state == 'GET BITS': # Wait until we're in the correct bit/sampling position. if not self.reached_bit(self.curbit): continue self.handle_bit(can_rx) else: raise Exception("Invalid state: %s" % self.state)