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+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2018 Stephan Thiele <stephan.thiele@mailbox.org>
+##
+## 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, see <http://www.gnu.org/licenses/>.
+##
+
+import sigrokdecode as srd
+
+class LinFsm:
+ class State:
+ WaitForBreak = 'WAIT FOR BREAK'
+ Sync = 'SYNC'
+ Pid = 'PID'
+ Data = 'DATA'
+ Checksum = 'CHECKSUM'
+ Error = 'ERROR'
+
+ def transit(self, target_state):
+ if not self._transition_allowed(target_state):
+ return False
+ self.state = target_state
+ return True
+
+ def _transition_allowed(self, target_state):
+ if target_state == LinFsm.State.Error:
+ return True
+ for s in self.allowed_state[self.state]:
+ if s == target_state:
+ return True
+ return False
+
+ def reset(self):
+ self.state = LinFsm.State.WaitForBreak
+
+ def __init__(self):
+ self.allowed_state = dict()
+ self.allowed_state[LinFsm.State.WaitForBreak] = (LinFsm.State.Sync,)
+ self.allowed_state[LinFsm.State.Sync] = (LinFsm.State.Pid,)
+ self.allowed_state[LinFsm.State.Pid] = (LinFsm.State.Data,)
+ self.allowed_state[LinFsm.State.Data] = (LinFsm.State.Data, LinFsm.State.Checksum)
+ self.allowed_state[LinFsm.State.Checksum] = (LinFsm.State.WaitForBreak,)
+ self.allowed_state[LinFsm.State.Error] = (LinFsm.State.Sync,)
+
+ self.state = None
+ self.reset()
+
+class Decoder(srd.Decoder):
+ api_version = 3
+ id = 'lin'
+ name = 'LIN'
+ longname = 'Local Interconnect Network'
+ desc = 'Local Interconnect Network (LIN) protocol.'
+ license = 'gplv2+'
+ inputs = ['uart']
+ outputs = ['lin']
+ options = (
+ {'id': 'version', 'desc': 'Protocol version', 'default': 2, 'values': (1, 2)},
+ )
+ annotations = (
+ ('data', 'LIN data'),
+ ('control', 'Protocol info'),
+ ('error', 'Error descriptions'),
+ ('inline_error', 'Protocol violations and errors'),
+ )
+ annotation_rows = (
+ ('data', 'Data', (0, 1, 3)),
+ ('error', 'Error', (2,)),
+ )
+
+ def __init__(self):
+ self.reset()
+
+ def reset(self):
+ self.fsm = LinFsm()
+ self.lin_header = []
+ self.lin_rsp = []
+ self.lin_version = None
+ self.out_ann = None
+ self.ss_block = None
+ self.es_block = None
+
+ def start(self):
+ self.out_ann = self.register(srd.OUTPUT_ANN)
+ self.lin_version = self.options['version']
+
+ def putx(self, data):
+ self.put(self.ss_block, self.es_block, self.out_ann, data)
+
+ def wipe_break_null_byte(self, value):
+ # Upon a break condition a null byte is received which must be ignored.
+ if self.fsm.state != LinFsm.State.WaitForBreak and self.fsm.state != LinFsm.State.Error:
+ if len(self.lin_rsp):
+ value = self.lin_rsp.pop()[2]
+ else:
+ self.lin_header.pop()
+
+ if value != 0:
+ self.fsm.transit(LinFsm.State.Error)
+ self.handle_error()
+ return False
+
+ return True
+
+ def handle_wait_for_break(self, value):
+ self.wipe_break_null_byte(value)
+
+ def handle_break(self, value):
+ if self.fsm.state != LinFsm.State.WaitForBreak and self.fsm.state != LinFsm.State.Error:
+ if self.wipe_break_null_byte(value):
+ self.fsm.transit(LinFsm.State.Checksum)
+ self.handle_checksum()
+
+ self.fsm.reset()
+ self.fsm.transit(LinFsm.State.Sync)
+
+ data = [1, ['Break condition', 'Break', 'Brk', 'B']]
+ self.put(self.ss_block, self.es_block, self.out_ann, data)
+
+ def handle_sync(self, value):
+ self.fsm.transit(LinFsm.State.Pid)
+ self.lin_header.append((self.ss_block, self.es_block, value))
+
+ def handle_pid(self, value):
+ self.fsm.transit(LinFsm.State.Data)
+ self.lin_header.append((self.ss_block, self.es_block, value))
+
+ def handle_data(self, value):
+ self.lin_rsp.append((self.ss_block, self.es_block, value))
+
+ def handle_checksum(self):
+ sync = self.lin_header.pop(0) if len(self.lin_header) else None
+
+ self.put(sync[0], sync[1], self.out_ann, [0, ['Sync', 'S']])
+
+ if sync[2] != 0x55:
+ self.put(sync[0], sync[1], self.out_ann,
+ [2, ['Sync is not 0x55', 'Not 0x55', '!= 0x55']])
+
+ pid = self.lin_header.pop(0) if len(self.lin_header) else None
+ checksum = self.lin_rsp.pop() if len(self.lin_rsp) else None
+
+ if pid:
+ id = pid[2] & 0x3F
+ parity = pid[2] >> 6
+
+ expected_parity = self.calc_parity(pid[2])
+ parity_valid = parity == expected_parity
+
+ if not parity_valid:
+ self.put(pid[0], pid[1], self.out_ann, [2, ['P != %d' % expected_parity]])
+
+ ann_class = 0 if parity_valid else 3
+ self.put(pid[0], pid[1], self.out_ann, [ann_class, [
+ 'ID: %02X Parity: %d (%s)' % (id, parity, 'ok' if parity_valid else 'bad'),
+ 'ID: 0x%02X' % id, 'I: %d' % id
+ ]])
+
+ if len(self.lin_rsp):
+ checksum_valid = self.checksum_is_valid(pid[2], self.lin_rsp, checksum[2])
+
+ for b in self.lin_rsp:
+ self.put(b[0], b[1], self.out_ann, [0, ['Data: 0x%02X' % b[2], 'D: 0x%02X' % b[2]]])
+
+ ann_class = 0 if checksum_valid else 3
+ self.put(checksum[0], checksum[1], self.out_ann,
+ [ann_class, ['Checksum: 0x%02X' % checksum[2], 'Checksum', 'Chk', 'C']])
+
+ if not checksum_valid:
+ self.put(checksum[0], checksum[1], self.out_ann, [2, ['Checksum invalid']])
+ else:
+ pass # No response.
+
+ self.lin_header.clear()
+ self.lin_rsp.clear()
+
+ def handle_error(self):
+ self.putx([3, ['Error', 'Err', 'E']])
+
+ def checksum_is_valid(self, pid, data, checksum):
+ if self.lin_version == 2:
+ id = pid & 0x3F
+
+ if id != 60 and id != 61:
+ checksum += pid
+
+ for d in data:
+ checksum += d[2]
+
+ carry_bits = int(checksum / 256)
+ checksum += carry_bits
+
+ return checksum & 0xFF == 0xFF
+
+ @staticmethod
+ def calc_parity(pid):
+ id = [((pid & 0x3F) >> i) & 1 for i in range(8)]
+
+ p0 = id[0] ^ id[1] ^ id[2] ^ id[4]
+ p1 = not (id[1] ^ id[3] ^ id[4] ^ id[5])
+
+ return (p0 << 0) | (p1 << 1)
+
+ def decode(self, ss, es, data):
+ ptype, rxtx, pdata = data
+
+ self.ss_block, self.es_block = ss, es
+
+ # Ignore all UART packets except the actual data packets or BREAK.
+ if ptype == 'BREAK':
+ self.handle_break(pdata)
+ if ptype != 'DATA':
+ return
+
+ # We're only interested in the byte value (not individual bits).
+ pdata = pdata[0]
+
+ # Short LIN overview:
+ # - Message begins with a BREAK (0x00) for at least 13 bittimes.
+ # - Break is always followed by a SYNC byte (0x55).
+ # - Sync byte is followed by a PID byte (Protected Identifier).
+ # - PID byte is followed by 1 - 8 data bytes and a final checksum byte.
+
+ if self.fsm.state == LinFsm.State.Error: self.handle_error()
+ elif self.fsm.state == LinFsm.State.WaitForBreak: self.handle_wait_for_break(pdata)
+ elif self.fsm.state == LinFsm.State.Sync: self.handle_sync(pdata)
+ elif self.fsm.state == LinFsm.State.Pid: self.handle_pid(pdata)
+ elif self.fsm.state == LinFsm.State.Data: self.handle_data(pdata)
+ elif self.fsm.state == LinFsm.State.Checksum: self.handle_checksum()
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