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##
## This file is part of the libsigrokdecode project.
##
## Copyright (C) 2013 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, write to the Free Software
## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
##
import sigrokdecode as srd
class SamplerateError(Exception):
pass
class Decoder(srd.Decoder):
api_version = 2
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']
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, **kwargs):
self.olddata = None
self.ss_edge = None
self.first_transition = True
self.bitwidth = 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, ss, es, data):
if not self.samplerate:
raise SamplerateError('Cannot decode without samplerate.')
for (self.samplenum, pins) in data:
data = pins[0]
# Wait for any transition on the data line.
if data == self.olddata:
continue
# Initialize first self.olddata with the first sample value.
if self.olddata is None:
self.olddata = data
continue
# Get the smallest distance between two transitions
# and use that to calculate the bitrate/baudrate.
if self.first_transition:
self.ss_edge = self.samplenum
self.first_transition = False
else:
b = self.samplenum - self.ss_edge
if self.bitwidth is None or b < self.bitwidth:
self.bitwidth = b
bitrate = int(float(self.samplerate) / float(b))
self.putx([0, ['%d' % bitrate]])
self.ss_edge = self.samplenum
self.olddata = data
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