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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, write to the Free Software
## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
##
import sigrokdecode as srd
class Decoder(srd.Decoder):
api_version = 2
id = 'pwm'
name = 'PWM'
longname = 'Pulse-width modulation'
desc = 'Analog level encoded in duty cycle percentage.'
license = 'gplv2+'
inputs = ['logic']
outputs = ['pwm']
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'),
)
binary = (
('raw', 'RAW file'),
)
def __init__(self, **kwargs):
self.ss = self.es = None
self.first_transition = True
self.first_samplenum = None
self.start_samplenum = None
self.end_samplenum = None
self.oldpin = None
self.num_cycles = 0
self.average = 0
def start(self):
self.startedge = 0 if self.options['polarity'] == 'active-low' else 1
self.out_ann = self.register(srd.OUTPUT_ANN)
self.out_bin = 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, self.es, self.out_ann, data)
def putb(self, data):
self.put(self.num_cycles, self.num_cycles, self.out_bin, data)
def decode(self, ss, es, data):
for (self.samplenum, pins) in data:
# Ignore identical samples early on (for performance reasons).
if self.oldpin == pins[0]:
continue
# Initialize self.oldpins with the first sample value.
if self.oldpin is None:
self.oldpin = pins[0]
continue
if self.first_transition:
# First rising edge
if self.oldpin != self.startedge:
self.first_samplenum = self.samplenum
self.start_samplenum = self.samplenum
self.first_transition = False
else:
if self.oldpin != self.startedge:
# Rising edge
# We are on a full cycle we can calculate
# the period, the duty cycle and its ratio.
period = self.samplenum - self.start_samplenum
duty = self.end_samplenum - self.start_samplenum
ratio = float(duty / period)
# This interval starts at this edge.
self.ss = self.start_samplenum
# Store the new rising edge position and the ending
# edge interval.
self.start_samplenum = self.es = self.samplenum
# 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)])))
# Update and report the new duty cycle average.
self.num_cycles += 1
self.average += percent
self.put(self.first_samplenum, self.es, self.out_average,
float(self.average / self.num_cycles))
else:
# Falling edge
self.end_samplenum = self.ss = self.samplenum
self.oldpin = pins[0]
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