2 ## This file is part of the libsigrokdecode project.
4 ## Copyright (C) 2018 Stephan Thiele <stephan.thiele@mailbox.org>
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
24 WaitForBreak = 'WAIT FOR BREAK'
31 def transit(self, target_state):
32 if not self._transition_allowed(target_state):
34 self.state = target_state
37 def _transition_allowed(self, target_state):
38 if target_state == LinFsm.State.Error:
40 for s in self.allowed_state[self.state]:
46 self.state = LinFsm.State.WaitForBreak
49 self.allowed_state = dict()
50 self.allowed_state[LinFsm.State.WaitForBreak] = (LinFsm.State.Sync,)
51 self.allowed_state[LinFsm.State.Sync] = (LinFsm.State.Pid,)
52 self.allowed_state[LinFsm.State.Pid] = (LinFsm.State.Data,)
53 self.allowed_state[LinFsm.State.Data] = (LinFsm.State.Data, LinFsm.State.Checksum)
54 self.allowed_state[LinFsm.State.Checksum] = (LinFsm.State.WaitForBreak,)
55 self.allowed_state[LinFsm.State.Error] = (LinFsm.State.Sync,)
60 class Decoder(srd.Decoder):
64 longname = 'Local Interconnect Network'
65 desc = 'Local Interconnect Network (LIN) protocol.'
70 {'id': 'version', 'desc': 'Protocol version', 'default': 2, 'values': (1, 2)},
74 ('control', 'Protocol info'),
75 ('error', 'Error descriptions'),
76 ('inline_error', 'Protocol violations and errors'),
79 ('data', 'Data', (0, 1, 3)),
80 ('error', 'Error', (2,)),
90 self.lin_version = None
96 self.out_ann = self.register(srd.OUTPUT_ANN)
97 self.lin_version = self.options['version']
100 self.put(self.ss_block, self.es_block, self.out_ann, data)
102 def wipe_break_null_byte(self, value):
103 # Upon a break condition a null byte is received which must be ignored.
104 if self.fsm.state != LinFsm.State.WaitForBreak and self.fsm.state != LinFsm.State.Error:
105 if len(self.lin_rsp):
106 value = self.lin_rsp.pop()[2]
108 self.lin_header.pop()
111 self.fsm.transit(LinFsm.State.Error)
117 def handle_wait_for_break(self, value):
118 self.wipe_break_null_byte(value)
120 def handle_break(self, value):
121 if self.fsm.state != LinFsm.State.WaitForBreak and self.fsm.state != LinFsm.State.Error:
122 if self.wipe_break_null_byte(value):
123 self.fsm.transit(LinFsm.State.Checksum)
124 self.handle_checksum()
127 self.fsm.transit(LinFsm.State.Sync)
129 data = [1, ['Break condition', 'Break', 'Brk', 'B']]
130 self.put(self.ss_block, self.es_block, self.out_ann, data)
132 def handle_sync(self, value):
133 self.fsm.transit(LinFsm.State.Pid)
134 self.lin_header.append((self.ss_block, self.es_block, value))
136 def handle_pid(self, value):
137 self.fsm.transit(LinFsm.State.Data)
138 self.lin_header.append((self.ss_block, self.es_block, value))
140 def handle_data(self, value):
141 self.lin_rsp.append((self.ss_block, self.es_block, value))
143 def handle_checksum(self):
144 sync = self.lin_header.pop(0) if len(self.lin_header) else None
146 self.put(sync[0], sync[1], self.out_ann, [0, ['Sync', 'S']])
149 self.put(sync[0], sync[1], self.out_ann,
150 [2, ['Sync is not 0x55', 'Not 0x55', '!= 0x55']])
152 pid = self.lin_header.pop(0) if len(self.lin_header) else None
153 checksum = self.lin_rsp.pop() if len(self.lin_rsp) else None
159 expected_parity = self.calc_parity(pid[2])
160 parity_valid = parity == expected_parity
163 self.put(pid[0], pid[1], self.out_ann, [2, ['P != %d' % expected_parity]])
165 ann_class = 0 if parity_valid else 3
166 self.put(pid[0], pid[1], self.out_ann, [ann_class, [
167 'ID: %02X Parity: %d (%s)' % (id, parity, 'ok' if parity_valid else 'bad'),
168 'ID: 0x%02X' % id, 'I: %d' % id
171 if len(self.lin_rsp):
172 checksum_valid = self.checksum_is_valid(pid[2], self.lin_rsp, checksum[2])
174 for b in self.lin_rsp:
175 self.put(b[0], b[1], self.out_ann, [0, ['Data: 0x%02X' % b[2], 'D: 0x%02X' % b[2]]])
177 ann_class = 0 if checksum_valid else 3
178 self.put(checksum[0], checksum[1], self.out_ann,
179 [ann_class, ['Checksum: 0x%02X' % checksum[2], 'Checksum', 'Chk', 'C']])
181 if not checksum_valid:
182 self.put(checksum[0], checksum[1], self.out_ann, [2, ['Checksum invalid']])
186 self.lin_header.clear()
189 def handle_error(self):
190 self.putx([3, ['Error', 'Err', 'E']])
192 def checksum_is_valid(self, pid, data, checksum):
193 if self.lin_version == 2:
196 if id != 60 and id != 61:
202 carry_bits = int(checksum / 256)
203 checksum += carry_bits
205 return checksum & 0xFF == 0xFF
208 def calc_parity(pid):
209 id = [((pid & 0x3F) >> i) & 1 for i in range(8)]
211 p0 = id[0] ^ id[1] ^ id[2] ^ id[4]
212 p1 = not (id[1] ^ id[3] ^ id[4] ^ id[5])
214 return (p0 << 0) | (p1 << 1)
216 def decode(self, ss, es, data):
217 ptype, rxtx, pdata = data
219 self.ss_block, self.es_block = ss, es
221 # Ignore all UART packets except the actual data packets or BREAK.
223 self.handle_break(pdata)
227 # We're only interested in the byte value (not individual bits).
230 # Short LIN overview:
231 # - Message begins with a BREAK (0x00) for at least 13 bittimes.
232 # - Break is always followed by a SYNC byte (0x55).
233 # - Sync byte is followed by a PID byte (Protected Identifier).
234 # - PID byte is followed by 1 - 8 data bytes and a final checksum byte.
236 if self.fsm.state == LinFsm.State.Error: self.handle_error()
237 elif self.fsm.state == LinFsm.State.WaitForBreak: self.handle_wait_for_break(pdata)
238 elif self.fsm.state == LinFsm.State.Sync: self.handle_sync(pdata)
239 elif self.fsm.state == LinFsm.State.Pid: self.handle_pid(pdata)
240 elif self.fsm.state == LinFsm.State.Data: self.handle_data(pdata)
241 elif self.fsm.state == LinFsm.State.Checksum: self.handle_checksum()