2 ## This file is part of the libsigrokdecode project.
4 ## Copyright (C) 2013-2016 Uwe Hermann <uwe@hermann-uwe.de>
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.
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.
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/>.
20 import sigrokdecode as srd
22 class SamplerateError(Exception):
25 class Decoder(srd.Decoder):
28 name = 'Guess bitrate'
29 longname = 'Guess bitrate/baudrate'
30 desc = 'Guess the bitrate/baudrate of a UART (or other) protocol.'
34 tags = ['Clock/timing', 'Util']
36 {'id': 'data', 'name': 'Data', 'desc': 'Data line'},
39 ('bitrate', 'Bitrate / baudrate'),
43 self.put(self.ss_edge, self.samplenum, self.out_ann, data)
52 self.out_ann = self.register(srd.OUTPUT_ANN)
54 def metadata(self, key, value):
55 if key == srd.SRD_CONF_SAMPLERATE:
56 self.samplerate = value
59 if not self.samplerate:
60 raise SamplerateError('Cannot decode without samplerate.')
62 # Get the first edge on the data line.
64 self.ss_edge = self.samplenum
66 # Get any subsequent edge on the data line. Get the smallest
67 # distance between any two transitions, assuming it corresponds
68 # to one bit time of the respective bitrate of the input stream.
69 # This heuristics keeps getting better for longer captures.
74 b = self.samplenum - self.ss_edge
75 if bitwidth is None or b < bitwidth:
77 bitrate = int(float(self.samplerate) / float(b))
78 self.putx([0, ['%d' % bitrate]])
79 self.ss_edge = self.samplenum