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1 | ## | |
2 | ## This file is part of the libsigrokdecode project. | |
3 | ## | |
4 | ## Copyright (C) 2018 Stephan Thiele <stephan.thiele@mailbox.org> | |
5 | ## | |
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. | |
10 | ## | |
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. | |
15 | ## | |
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/>. | |
18 | ## | |
19 | ||
20 | import sigrokdecode as srd | |
21 | ||
22 | class LinFsm: | |
23 | class State: | |
24 | WaitForBreak = 'WAIT_FOR_BREAK' | |
25 | Sync = 'SYNC' | |
26 | Pid = 'PID' | |
27 | Data = 'DATA' | |
28 | Checksum = 'CHECKSUM' | |
29 | Error = 'ERROR' | |
30 | ||
31 | def transit(self, target_state): | |
32 | if not self._transition_allowed(target_state): | |
33 | return False | |
34 | self.state = target_state | |
35 | return True | |
36 | ||
37 | def _transition_allowed(self, target_state): | |
38 | if target_state == LinFsm.State.Error: | |
39 | return True | |
40 | return target_state in self.allowed_state[self.state] | |
41 | ||
42 | def reset(self): | |
43 | self.state = LinFsm.State.WaitForBreak | |
44 | ||
45 | def __init__(self): | |
46 | a = dict() | |
47 | a[LinFsm.State.WaitForBreak] = (LinFsm.State.Sync,) | |
48 | a[LinFsm.State.Sync] = (LinFsm.State.Pid,) | |
49 | a[LinFsm.State.Pid] = (LinFsm.State.Data,) | |
50 | a[LinFsm.State.Data] = (LinFsm.State.Data, LinFsm.State.Checksum) | |
51 | a[LinFsm.State.Checksum] = (LinFsm.State.WaitForBreak,) | |
52 | a[LinFsm.State.Error] = (LinFsm.State.Sync,) | |
53 | self.allowed_state = a | |
54 | ||
55 | self.state = None | |
56 | self.reset() | |
57 | ||
58 | class Decoder(srd.Decoder): | |
59 | api_version = 3 | |
60 | id = 'lin' | |
61 | name = 'LIN' | |
62 | longname = 'Local Interconnect Network' | |
63 | desc = 'Local Interconnect Network (LIN) protocol.' | |
64 | license = 'gplv2+' | |
65 | inputs = ['uart'] | |
66 | outputs = [] | |
67 | tags = ['Automotive'] | |
68 | options = ( | |
69 | {'id': 'version', 'desc': 'Protocol version', 'default': 2, 'values': (1, 2)}, | |
70 | ) | |
71 | annotations = ( | |
72 | ('data', 'LIN data'), | |
73 | ('control', 'Protocol info'), | |
74 | ('error', 'Error descriptions'), | |
75 | ('inline_error', 'Protocol violations and errors'), | |
76 | ) | |
77 | annotation_rows = ( | |
78 | ('data', 'Data', (0, 1, 3)), | |
79 | ('error', 'Error', (2,)), | |
80 | ) | |
81 | ||
82 | def __init__(self): | |
83 | self.reset() | |
84 | ||
85 | def reset(self): | |
86 | self.fsm = LinFsm() | |
87 | self.lin_header = [] | |
88 | self.lin_rsp = [] | |
89 | self.lin_version = None | |
90 | self.out_ann = None | |
91 | self.ss_block = None | |
92 | self.es_block = None | |
93 | ||
94 | def start(self): | |
95 | self.out_ann = self.register(srd.OUTPUT_ANN) | |
96 | self.lin_version = self.options['version'] | |
97 | ||
98 | def putx(self, data): | |
99 | self.put(self.ss_block, self.es_block, self.out_ann, data) | |
100 | ||
101 | def wipe_break_null_byte(self, value): | |
102 | # Upon a break condition a null byte is received which must be ignored. | |
103 | if self.fsm.state not in (LinFsm.State.WaitForBreak, LinFsm.State.Error): | |
104 | if len(self.lin_rsp): | |
105 | value = self.lin_rsp.pop()[2] | |
106 | else: | |
107 | self.lin_header.pop() | |
108 | ||
109 | if value != 0: | |
110 | self.fsm.transit(LinFsm.State.Error) | |
111 | self.handle_error(None) | |
112 | return False | |
113 | ||
114 | return True | |
115 | ||
116 | def handle_wait_for_break(self, value): | |
117 | self.wipe_break_null_byte(value) | |
118 | ||
119 | def handle_break(self, value): | |
120 | if self.fsm.state not in (LinFsm.State.WaitForBreak, LinFsm.State.Error): | |
121 | if self.wipe_break_null_byte(value): | |
122 | self.fsm.transit(LinFsm.State.Checksum) | |
123 | self.handle_checksum() | |
124 | ||
125 | self.fsm.reset() | |
126 | self.fsm.transit(LinFsm.State.Sync) | |
127 | ||
128 | self.putx([1, ['Break condition', 'Break', 'Brk', 'B']]) | |
129 | ||
130 | def handle_sync(self, value): | |
131 | self.fsm.transit(LinFsm.State.Pid) | |
132 | self.lin_header.append((self.ss_block, self.es_block, value)) | |
133 | ||
134 | def handle_pid(self, value): | |
135 | self.fsm.transit(LinFsm.State.Data) | |
136 | self.lin_header.append((self.ss_block, self.es_block, value)) | |
137 | ||
138 | def handle_data(self, value): | |
139 | self.lin_rsp.append((self.ss_block, self.es_block, value)) | |
140 | ||
141 | def handle_checksum(self): | |
142 | sync = self.lin_header.pop(0) if len(self.lin_header) else None | |
143 | ||
144 | self.put(sync[0], sync[1], self.out_ann, [0, ['Sync', 'S']]) | |
145 | ||
146 | if sync[2] != 0x55: | |
147 | self.put(sync[0], sync[1], self.out_ann, | |
148 | [2, ['Sync is not 0x55', 'Not 0x55', '!= 0x55']]) | |
149 | ||
150 | pid = self.lin_header.pop(0) if len(self.lin_header) else None | |
151 | checksum = self.lin_rsp.pop() if len(self.lin_rsp) else None | |
152 | ||
153 | if pid: | |
154 | id_ = pid[2] & 0x3F | |
155 | parity = pid[2] >> 6 | |
156 | ||
157 | expected_parity = self.calc_parity(pid[2]) | |
158 | parity_valid = parity == expected_parity | |
159 | ||
160 | if not parity_valid: | |
161 | self.put(pid[0], pid[1], self.out_ann, [2, ['P != %d' % expected_parity]]) | |
162 | ||
163 | ann_class = 0 if parity_valid else 3 | |
164 | self.put(pid[0], pid[1], self.out_ann, [ann_class, [ | |
165 | 'ID: %02X Parity: %d (%s)' % (id_, parity, 'ok' if parity_valid else 'bad'), | |
166 | 'ID: 0x%02X' % id_, 'I: %d' % id_ | |
167 | ]]) | |
168 | ||
169 | if len(self.lin_rsp): | |
170 | checksum_valid = self.checksum_is_valid(pid[2], self.lin_rsp, checksum[2]) | |
171 | ||
172 | for b in self.lin_rsp: | |
173 | self.put(b[0], b[1], self.out_ann, [0, ['Data: 0x%02X' % b[2], 'D: 0x%02X' % b[2]]]) | |
174 | ||
175 | ann_class = 0 if checksum_valid else 3 | |
176 | self.put(checksum[0], checksum[1], self.out_ann, | |
177 | [ann_class, ['Checksum: 0x%02X' % checksum[2], 'Checksum', 'Chk', 'C']]) | |
178 | ||
179 | if not checksum_valid: | |
180 | self.put(checksum[0], checksum[1], self.out_ann, [2, ['Checksum invalid']]) | |
181 | else: | |
182 | pass # No response. | |
183 | ||
184 | self.lin_header.clear() | |
185 | self.lin_rsp.clear() | |
186 | ||
187 | def handle_error(self, dummy): | |
188 | self.putx([3, ['Error', 'Err', 'E']]) | |
189 | ||
190 | def checksum_is_valid(self, pid, data, checksum): | |
191 | if self.lin_version == 2: | |
192 | id_ = pid & 0x3F | |
193 | ||
194 | if id_ != 60 and id_ != 61: | |
195 | checksum += pid | |
196 | ||
197 | for d in data: | |
198 | checksum += d[2] | |
199 | ||
200 | carry_bits = int(checksum / 256) | |
201 | checksum += carry_bits | |
202 | ||
203 | return checksum & 0xFF == 0xFF | |
204 | ||
205 | @staticmethod | |
206 | def calc_parity(pid): | |
207 | id_ = [((pid & 0x3F) >> i) & 1 for i in range(8)] | |
208 | ||
209 | p0 = id_[0] ^ id_[1] ^ id_[2] ^ id_[4] | |
210 | p1 = not (id_[1] ^ id_[3] ^ id_[4] ^ id_[5]) | |
211 | ||
212 | return (p0 << 0) | (p1 << 1) | |
213 | ||
214 | def decode(self, ss, es, data): | |
215 | ptype, rxtx, pdata = data | |
216 | ||
217 | self.ss_block, self.es_block = ss, es | |
218 | ||
219 | # Ignore all UART packets except the actual data packets or BREAK. | |
220 | if ptype == 'BREAK': | |
221 | self.handle_break(pdata) | |
222 | if ptype != 'DATA': | |
223 | return | |
224 | ||
225 | # We're only interested in the byte value (not individual bits). | |
226 | pdata = pdata[0] | |
227 | ||
228 | # Short LIN overview: | |
229 | # - Message begins with a BREAK (0x00) for at least 13 bittimes. | |
230 | # - Break is always followed by a SYNC byte (0x55). | |
231 | # - Sync byte is followed by a PID byte (Protected Identifier). | |
232 | # - PID byte is followed by 1 - 8 data bytes and a final checksum byte. | |
233 | ||
234 | handler = getattr(self, 'handle_%s' % self.fsm.state.lower()) | |
235 | handler(pdata) |