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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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