mirror of
https://github.com/DreamSourceLab/DSView.git
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142 lines
4.7 KiB
Python
Executable File
142 lines
4.7 KiB
Python
Executable File
##
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## This file is part of the libsigrokdecode project.
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##
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## Copyright (C) 2014 Torsten Duwe <duwe@suse.de>
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## Copyright (C) 2014 Sebastien Bourdelin <sebastien.bourdelin@savoirfairelinux.com>
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##
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## This program is free software; you can redistribute it and/or modify
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## it under the terms of the GNU General Public License as published by
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## the Free Software Foundation; either version 2 of the License, or
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## (at your option) any later version.
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##
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## This program is distributed in the hope that it will be useful,
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## but WITHOUT ANY WARRANTY; without even the implied warranty of
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## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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## GNU General Public License for more details.
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##
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## You should have received a copy of the GNU General Public License
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## along with this program; if not, see <http://www.gnu.org/licenses/>.
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##
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import sigrokdecode as srd
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class SamplerateError(Exception):
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pass
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class Decoder(srd.Decoder):
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api_version = 3
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id = 'pwm'
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name = 'PWM'
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longname = 'Pulse-width modulation'
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desc = 'Analog level encoded in duty cycle percentage.'
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license = 'gplv2+'
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inputs = ['logic']
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outputs = []
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tags = ['Encoding']
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channels = (
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{'id': 'data', 'name': 'Data', 'desc': 'Data line'},
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)
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options = (
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{'id': 'polarity', 'desc': 'Polarity', 'default': 'active-high',
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'values': ('active-low', 'active-high')},
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)
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annotations = (
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('duty-cycle', 'Duty cycle'),
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('period', 'Period'),
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)
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annotation_rows = (
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('duty-cycle', 'Duty cycle', (0,)),
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('period', 'Period', (1,)),
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)
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binary = (
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('raw', 'RAW file'),
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)
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def __init__(self):
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self.reset()
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def reset(self):
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self.samplerate = None
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self.ss_block = self.es_block = None
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def metadata(self, key, value):
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if key == srd.SRD_CONF_SAMPLERATE:
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self.samplerate = value
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def start(self):
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self.out_ann = self.register(srd.OUTPUT_ANN)
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self.out_binary = self.register(srd.OUTPUT_BINARY)
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self.out_average = \
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self.register(srd.OUTPUT_META,
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meta=(float, 'Average', 'PWM base (cycle) frequency'))
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def putx(self, data):
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self.put(self.ss_block, self.es_block, self.out_ann, data)
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def putp(self, period_t):
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# Adjust granularity.
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if period_t == 0 or period_t >= 1:
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period_s = '%.1f s' % (period_t)
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elif period_t <= 1e-12:
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period_s = '%.1f fs' % (period_t * 1e15)
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elif period_t <= 1e-9:
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period_s = '%.1f ps' % (period_t * 1e12)
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elif period_t <= 1e-6:
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period_s = '%.1f ns' % (period_t * 1e9)
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elif period_t <= 1e-3:
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period_s = '%.1f μs' % (period_t * 1e6)
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else:
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period_s = '%.1f ms' % (period_t * 1e3)
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self.put(self.ss_block, self.es_block, self.out_ann, [1, [period_s]])
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def putb(self, data):
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self.put(self.ss_block, self.es_block, self.out_binary, data)
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def decode(self):
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if not self.samplerate:
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raise SamplerateError('Cannot decode without samplerate.')
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num_cycles = 0
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average = 0
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# Wait for an "active" edge (depends on config). This starts
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# the first full period of the inspected signal waveform.
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self.wait({0: 'f' if self.options['polarity'] == 'active-low' else 'r'})
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self.first_samplenum = self.samplenum
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# Keep getting samples for the period's middle and terminal edges.
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# At the same time that last sample starts the next period.
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while True:
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# Get the next two edges. Setup some variables that get
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# referenced in the calculation and in put() routines.
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start_samplenum = self.samplenum
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self.wait({0: 'e'})
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end_samplenum = self.samplenum
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self.wait({0: 'e'})
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self.ss_block = start_samplenum
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self.es_block = self.samplenum
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# Calculate the period, the duty cycle, and its ratio.
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period = self.samplenum - start_samplenum
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duty = end_samplenum - start_samplenum
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ratio = float(duty / period)
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# Report the duty cycle in percent.
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percent = float(ratio * 100)
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self.putx([0, ['%f%%' % percent]])
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# Report the duty cycle in the binary output.
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self.putb([0, bytes([int(ratio * 256)])])
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# Report the period in units of time.
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period_t = float(period / self.samplerate)
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self.putp(period_t)
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# Update and report the new duty cycle average.
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num_cycles += 1
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average += percent
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self.put(self.first_samplenum, self.es_block, self.out_average,
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float(average / num_cycles))
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