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##
## This file is part of the libsigrokdecode project.
##
## Copyright (C) 2013-2016 Uwe Hermann <uwe@hermann-uwe.de>
##
## 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
class Decoder(srd.Decoder):
api_version = 3
id = 'guess_bitrate'
name = 'Guess bitrate'
longname = 'Guess bitrate/baudrate'
desc = 'Guess the bitrate/baudrate of a UART (or other) protocol.'
license = 'gplv2+'
inputs = ['logic']
outputs = ['guess_bitrate']
tags = ['Clock/timing', 'Util']
channels = (
{'id': 'data', 'name': 'Data', 'desc': 'Data line'},
)
annotations = (
('bitrate', 'Bitrate / baudrate'),
)
def putx(self, data):
self.put(self.ss_edge, self.samplenum, self.out_ann, data)
def __init__(self):
self.reset()
def reset(self):
self.ss_edge = None
def start(self):
self.out_ann = self.register(srd.OUTPUT_ANN)
def metadata(self, key, value):
if key == srd.SRD_CONF_SAMPLERATE:
self.samplerate = value
def decode(self):
if not self.samplerate:
raise SamplerateError('Cannot decode without samplerate.')
# Get the first edge on the data line.
self.wait({0: 'e'})
self.ss_edge = self.samplenum
# Get any subsequent edge on the data line. Get the smallest
# distance between any two transitions, assuming it corresponds
# to one bit time of the respective bitrate of the input stream.
# This heuristics keeps getting better for longer captures.
bitwidth = None
while True:
self.wait({0: 'e'})
b = self.samplenum - self.ss_edge
if bitwidth is None or b < bitwidth:
bitwidth = b
bitrate = int(float(self.samplerate) / float(b))
self.putx([0, ['%d' % bitrate]])
self.ss_edge = self.samplenum
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