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##
## This file is part of the libsigrokdecode project.
##
## Copyright (C) 2014 Torsten Duwe <duwe@suse.de>
## Copyright (C) 2014 Sebastien Bourdelin <sebastien.bourdelin@savoirfairelinux.com>
##
## 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 = 'pwm'
name = 'PWM'
longname = 'Pulse-width modulation'
desc = 'Analog level encoded in duty cycle percentage.'
license = 'gplv2+'
inputs = ['logic']
outputs = []
tags = ['Encoding']
channels = (
{'id': 'data', 'name': 'Data', 'desc': 'Data line'},
)
options = (
{'id': 'polarity', 'desc': 'Polarity', 'default': 'active-high',
'values': ('active-low', 'active-high')},
)
annotations = (
('duty-cycle', 'Duty cycle'),
('period', 'Period'),
)
annotation_rows = (
('duty-cycle', 'Duty cycle', (0,)),
('period', 'Period', (1,)),
)
binary = (
('raw', 'RAW file'),
)
def __init__(self):
self.reset()
def reset(self):
self.samplerate = None
self.ss_block = self.es_block = None
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)
self.out_binary = self.register(srd.OUTPUT_BINARY)
self.out_average = \
self.register(srd.OUTPUT_META,
meta=(float, 'Average', 'PWM base (cycle) frequency'))
def putx(self, data):
self.put(self.ss_block, self.es_block, self.out_ann, data)
def putp(self, period_t):
# Adjust granularity.
if period_t == 0 or period_t >= 1:
period_s = '%.1f s' % (period_t)
elif period_t <= 1e-12:
period_s = '%.1f fs' % (period_t * 1e15)
elif period_t <= 1e-9:
period_s = '%.1f ps' % (period_t * 1e12)
elif period_t <= 1e-6:
period_s = '%.1f ns' % (period_t * 1e9)
elif period_t <= 1e-3:
period_s = '%.1f μs' % (period_t * 1e6)
else:
period_s = '%.1f ms' % (period_t * 1e3)
self.put(self.ss_block, self.es_block, self.out_ann, [1, [period_s]])
def putb(self, data):
self.put(self.ss_block, self.es_block, self.out_binary, data)
def decode(self):
if not self.samplerate:
raise SamplerateError('Cannot decode without samplerate.')
num_cycles = 0
average = 0
# Wait for an "active" edge (depends on config). This starts
# the first full period of the inspected signal waveform.
self.wait({0: 'f' if self.options['polarity'] == 'active-low' else 'r'})
self.first_samplenum = self.samplenum
# Keep getting samples for the period's middle and terminal edges.
# At the same time that last sample starts the next period.
while True:
# Get the next two edges. Setup some variables that get
# referenced in the calculation and in put() routines.
start_samplenum = self.samplenum
self.wait({0: 'e'})
end_samplenum = self.samplenum
self.wait({0: 'e'})
self.ss_block = start_samplenum
self.es_block = self.samplenum
# Calculate the period, the duty cycle, and its ratio.
period = self.samplenum - start_samplenum
duty = end_samplenum - start_samplenum
ratio = float(duty / period)
# Report the duty cycle in percent.
percent = float(ratio * 100)
self.putx([0, ['%f%%' % percent]])
# Report the duty cycle in the binary output.
self.putb([0, bytes([int(ratio * 256)])])
# Report the period in units of time.
period_t = float(period / self.samplerate)
self.putp(period_t)
# Update and report the new duty cycle average.
num_cycles += 1
average += percent
self.put(self.first_samplenum, self.es_block, self.out_average,
float(average / num_cycles))
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