decoders/lin/pd.py

   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         self.uart_idle_count = 0
  45
  46     def __init__(self):
  47         a = dict()
  48         a[LinFsm.State.WaitForBreak] = (LinFsm.State.Sync,)
  49         a[LinFsm.State.Sync]         = (LinFsm.State.Pid,)
  50         a[LinFsm.State.Pid]          = (LinFsm.State.Data,)
  51         a[LinFsm.State.Data]         = (LinFsm.State.Data, LinFsm.State.Checksum)
  52         a[LinFsm.State.Checksum]     = (LinFsm.State.WaitForBreak,)
  53         a[LinFsm.State.Error]        = (LinFsm.State.Sync,)
  54         self.allowed_state = a
  55
  56         self.state = None
  57         self.uart_idle_count = 0
  58         self.reset()
  59
  60 class Decoder(srd.Decoder):
  61     api_version = 3
  62     id = 'lin'
  63     name = 'LIN'
  64     longname = 'Local Interconnect Network'
  65     desc = 'Local Interconnect Network (LIN) protocol.'
  66     license = 'gplv2+'
  67     inputs = ['uart']
  68     outputs = []
  69     tags = ['Automotive']
  70     options = (
  71         {'id': 'version', 'desc': 'Protocol version', 'default': 2, 'values': (1, 2)},
  72     )
  73     annotations = (
  74         ('data', 'LIN data'),
  75         ('control', 'Protocol info'),
  76         ('error', 'Error description'),
  77         ('inline_error', 'Protocol violation or error'),
  78     )
  79     annotation_rows = (
  80         ('data_vals', 'Data', (0, 1, 3)),
  81         ('errors', 'Errors', (2,)),
  82     )
  83
  84     def __init__(self):
  85         self.reset()
  86
  87     def reset(self):
  88         self.fsm = LinFsm()
  89         self.lin_header = []
  90         self.lin_rsp = []
  91         self.lin_version = None
  92         self.ss_block = None
  93         self.es_block = None
  94
  95     def start(self):
  96         self.out_ann = self.register(srd.OUTPUT_ANN)
  97         self.lin_version = self.options['version']
  98
  99     def putx(self, data):
 100         self.put(self.ss_block, self.es_block, self.out_ann, data)
 101
 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 not in (LinFsm.State.WaitForBreak, LinFsm.State.Error):
 105             if len(self.lin_rsp):
 106                 value = self.lin_rsp.pop()[2]
 107             else:
 108                 self.lin_header.pop()
 109
 110         if value != 0:
 111             self.fsm.transit(LinFsm.State.Error)
 112             self.handle_error(None)
 113             return False
 114
 115         return True
 116
 117     def handle_uart_idle(self):
 118         if self.fsm.state not in (LinFsm.State.WaitForBreak, LinFsm.State.Error):
 119             self.fsm.uart_idle_count += 1
 120
 121             if self.fsm.uart_idle_count == 2:
 122                 self.fsm.transit(LinFsm.State.Checksum)
 123                 self.handle_checksum()
 124                 self.fsm.reset()
 125
 126     def handle_wait_for_break(self, value):
 127         self.wipe_break_null_byte(value)
 128
 129     def handle_break(self, value):
 130         if self.fsm.state not in (LinFsm.State.WaitForBreak, LinFsm.State.Error):
 131             if self.wipe_break_null_byte(value):
 132                 self.fsm.transit(LinFsm.State.Checksum)
 133                 self.handle_checksum()
 134
 135         self.fsm.reset()
 136         self.fsm.transit(LinFsm.State.Sync)
 137
 138         self.putx([1, ['Break condition', 'Break', 'Brk', 'B']])
 139
 140     def handle_sync(self, value):
 141         self.fsm.transit(LinFsm.State.Pid)
 142         self.lin_header.append((self.ss_block, self.es_block, value))
 143
 144     def handle_pid(self, value):
 145         self.fsm.transit(LinFsm.State.Data)
 146         self.lin_header.append((self.ss_block, self.es_block, value))
 147
 148     def handle_data(self, value):
 149         self.lin_rsp.append((self.ss_block, self.es_block, value))
 150
 151     def handle_checksum(self):
 152         sync = self.lin_header.pop(0) if len(self.lin_header) else None
 153
 154         self.put(sync[0], sync[1], self.out_ann, [0, ['Sync', 'S']])
 155
 156         if sync[2] != 0x55:
 157             self.put(sync[0], sync[1], self.out_ann,
 158                      [2, ['Sync is not 0x55', 'Not 0x55', '!= 0x55']])
 159
 160         pid = self.lin_header.pop(0) if len(self.lin_header) else None
 161         checksum = self.lin_rsp.pop() if len(self.lin_rsp) else None
 162
 163         if pid:
 164             id_ = pid[2] & 0x3F
 165             parity = pid[2] >> 6
 166
 167             expected_parity = self.calc_parity(pid[2])
 168             parity_valid = parity == expected_parity
 169
 170             if not parity_valid:
 171                 self.put(pid[0], pid[1], self.out_ann, [2, ['P != %d' % expected_parity]])
 172
 173             ann_class = 0 if parity_valid else 3
 174             self.put(pid[0], pid[1], self.out_ann, [ann_class, [
 175                 'ID: %02X Parity: %d (%s)' % (id_, parity, 'ok' if parity_valid else 'bad'),
 176                 'ID: 0x%02X' % id_, 'I: %d' % id_
 177             ]])
 178
 179         if len(self.lin_rsp):
 180             checksum_valid = self.checksum_is_valid(pid[2], self.lin_rsp, checksum[2])
 181
 182             for b in self.lin_rsp:
 183                 self.put(b[0], b[1], self.out_ann, [0, ['Data: 0x%02X' % b[2], 'D: 0x%02X' % b[2]]])
 184
 185             ann_class = 0 if checksum_valid else 3
 186             self.put(checksum[0], checksum[1], self.out_ann,
 187                  [ann_class, ['Checksum: 0x%02X' % checksum[2], 'Checksum', 'Chk', 'C']])
 188
 189             if not checksum_valid:
 190                 self.put(checksum[0], checksum[1], self.out_ann, [2, ['Checksum invalid']])
 191         else:
 192             pass # No response.
 193
 194         self.lin_header.clear()
 195         self.lin_rsp.clear()
 196
 197     def handle_error(self, dummy):
 198         self.putx([3, ['Error', 'Err', 'E']])
 199
 200     def checksum_is_valid(self, pid, data, checksum):
 201         if self.lin_version == 2:
 202             id_ = pid & 0x3F
 203
 204             if id_ != 60 and id_ != 61:
 205                 checksum += pid
 206
 207         for d in data:
 208             checksum += d[2]
 209
 210         carry_bits = int(checksum / 256)
 211         checksum += carry_bits
 212
 213         return checksum & 0xFF == 0xFF
 214
 215     @staticmethod
 216     def calc_parity(pid):
 217         id_ = [((pid & 0x3F) >> i) & 1 for i in range(8)]
 218
 219         p0 = id_[0] ^ id_[1] ^ id_[2] ^ id_[4]
 220         p1 = not (id_[1] ^ id_[3] ^ id_[4] ^ id_[5])
 221
 222         return (p0 << 0) | (p1 << 1)
 223
 224     def decode(self, ss, es, data):
 225         ptype, rxtx, pdata = data
 226
 227         self.ss_block, self.es_block = ss, es
 228
 229         # Ignore all UART packets except the actual data packets or BREAK.
 230         if ptype == 'IDLE':
 231             self.handle_uart_idle()
 232         if ptype == 'BREAK':
 233             self.handle_break(pdata)
 234         if ptype != 'DATA':
 235             return
 236
 237         # We're only interested in the byte value (not individual bits).
 238         pdata = pdata[0]
 239
 240         # Short LIN overview:
 241         #  - Message begins with a BREAK (0x00) for at least 13 bittimes.
 242         #  - Break is always followed by a SYNC byte (0x55).
 243         #  - Sync byte is followed by a PID byte (Protected Identifier).
 244         #  - PID byte is followed by 1 - 8 data bytes and a final checksum byte.
 245
 246         handler = getattr(self, 'handle_%s' % self.fsm.state.lower())
 247         handler(pdata)