--- /dev/null
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2016 Anthony Symons <antus@pcmhacking.net>
+##
+## 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 SamplerateError(Exception):
+ pass
+
+def timeuf(t):
+ return int (t * 1000.0 * 1000.0)
+
+def normalize_time(t):
+ if t >= 1.0:
+ return '%d s' % t
+ elif t >= 0.001:
+ return '%d ms' % (t * 1000.0)
+ elif t >= 0.000001:
+ return '%d μs' % (t * 1000.0 * 1000.0)
+ elif t >= 0.000000001:
+ return '%d ns' % (t * 1000.0 * 1000.0 * 1000.0)
+ else:
+ return '%f' % t
+
+class Decoder(srd.Decoder):
+ api_version = 3
+ id = 'sae_j1850_vpw'
+ name = 'SAE J1850 VPW'
+ longname = 'SAE J1850 VPW.'
+ desc = 'SAE J1850 Variable Pulse Width 1x and 4x.'
+ license = 'gplv2+'
+ inputs = ['logic']
+ outputs = []
+ tags = ['Automotive']
+ channels = (
+ {'id': 'data', 'name': 'Data', 'desc': 'Data line'},
+ )
+ annotations = (
+ ('time', 'Time'),
+ ('raw', 'Raw'),
+ ('sof', 'SOF'),
+ ('ifs', 'EOF/IFS'),
+ ('data', 'Data'),
+ ('packet', 'Packet'),
+ )
+ annotation_rows = (
+ ('packets', 'Packets', (5,)),
+ ('bytes', 'Bytes', (4,)),
+ ('raws', 'Raws', (1,2,3,)),
+ ('times', 'Times', (0,)),
+ )
+
+ def __init__(self):
+ self.reset()
+
+ def reset(self):
+ self.state = 'IDLE'
+ self.samplerate = None
+ self.byte = 0 # the byte offset in the packet
+ self.mode = 0 # for by packet decode
+ self.data = 0 # the current byte
+ self.datastart = 0 # sample number this byte started at
+ self.csa = 0 # track the last byte seperately to retrospectively add the CS marker
+ self.csb = 0
+ self.count = 0 # which bit number we are up to
+ self.active = 0 # which logic level is considered active
+
+ # vpw timings. ideal, min and max tollerances.
+ # From SAE J1850 1995 rev section 23.406
+
+ self.sof = 200
+ self.sofl = 164
+ self.sofh = 245 # 240 by the spec, 245 so a 60us 4x sample will pass
+ self.long = 128
+ self.longl = 97
+ self.longh = 170 # 164 by the spec but 170 for low sample rate tolerance.
+ self.short = 64
+ self.shortl = 24 # 35 by the spec, 24 to allow down to 6us as measured in practice for 4x @ 1mhz sampling
+ self.shorth = 97
+ self.ifs = 240
+ self.spd = 1 # set to 4 when a 4x SOF is detected (VPW high speed frame)
+
+ def handle_bit(self, ss, es, b):
+ self.data |= (b << 7-self.count) # MSB-first
+ self.put(ss, es, self.out_ann, [1, ["%d" % b]])
+ if self.count == 0:
+ self.datastart = ss
+ if self.count == 7:
+ self.csa = self.datastart # for CS
+ self.csb = self.samplenum # for CS
+ self.put(self.datastart, self.samplenum, self.out_ann, [4, ["%02X" % self.data]])
+ # add protocol parsing here
+ if self.byte == 0:
+ self.put(self.datastart, self.samplenum, self.out_ann, [5, ['Priority','Prio','P']])
+ elif self.byte == 1:
+ self.put(self.datastart, self.samplenum, self.out_ann, [5, ['Destination','Dest','D']])
+ elif self.byte == 2:
+ self.put(self.datastart, self.samplenum, self.out_ann, [5, ['Source','Src','S']])
+ elif self.byte == 3:
+ self.put(self.datastart, self.samplenum, self.out_ann, [5, ['Mode','M']])
+ self.mode = self.data
+ elif self.mode == 1 and self.byte == 4: # mode 1 payload
+ self.put(self.datastart, self.samplenum, self.out_ann, [5, ['Pid','P']])
+
+ # prepare for next byte
+ self.count = -1
+ self.data = 0
+ self.byte = self.byte + 1 # track packet offset
+ self.count = self.count + 1
+
+ def metadata(self, key, value):
+ if key == srd.SRD_CONF_SAMPLERATE:
+ self.samplerate = value
+
+ def start(self):
+ self.out_ann = self.register(srd.OUTPUT_ANN)
+
+ def decode(self):
+ if not self.samplerate:
+ raise SamplerateError('Cannot decode without samplerate.')
+
+ self.wait({0: 'e'})
+ es = self.samplenum
+ while True:
+ ss = es
+ pin, = self.wait({0: 'e'})
+ es = self.samplenum
+
+ samples = es - ss
+ txt = normalize_time(samples / self.samplerate)
+ self.put(ss, es, self.out_ann, [0, [txt]])
+ t = timeuf(samples / self.samplerate)
+ if self.state == 'IDLE': # detect and set speed from the size of sof
+ if pin == self.active and t in range(self.sofl , self.sofh):
+ self.put(ss, es, self.out_ann, [1, ['1X SOF', 'S1', 'S']])
+ self.spd = 1
+ self.data = 0
+ self.count = 0
+ self.state = 'DATA'
+ elif pin == self.active and t in range(int(self.sofl / 4) , int(self.sofh / 4)):
+ self.put(ss, es, self.out_ann, [1, ['4X SOF', 'S4', '4']])
+ self.spd = 4
+ self.data = 0
+ self.count = 0
+ self.state = 'DATA'
+
+ elif self.state == 'DATA':
+ if t >= int(self.ifs / self.spd):
+ self.state = 'IDLE'
+ self.put(ss, es, self.out_ann, [1, ["EOF/IFS", "E"]]) # EOF=239-280 IFS=281+
+ self.put(self.csa, self.csb, self.out_ann, [5, ['Checksum','CS','C']]) # retrospective print of CS
+ self.byte = 0 # reset packet offset
+ elif t in range(int(self.shortl / self.spd), int(self.shorth / self.spd)):
+ if pin == self.active:
+ self.handle_bit(ss, es, 1)
+ else:
+ self.handle_bit(ss, es, 0)
+ elif t in range(int(self.longl / self.spd), int(self.longh / self.spd)):
+ if pin == self.active:
+ self.handle_bit(ss, es, 0)
+ else:
+ self.handle_bit(ss, es, 1)
projects / libsigrokdecode.git / blobdiff