2 ## This file is part of the libsigrokdecode project.
4 ## Copyright (C) 2014 Torsten Duwe <duwe@suse.de>
5 ## Copyright (C) 2014 Sebastien Bourdelin <sebastien.bourdelin@savoirfairelinux.com>
7 ## This program is free software; you can redistribute it and/or modify
8 ## it under the terms of the GNU General Public License as published by
9 ## the Free Software Foundation; either version 2 of the License, or
10 ## (at your option) any later version.
12 ## This program is distributed in the hope that it will be useful,
13 ## but WITHOUT ANY WARRANTY; without even the implied warranty of
14 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 ## GNU General Public License for more details.
17 ## You should have received a copy of the GNU General Public License
18 ## along with this program; if not, see <http://www.gnu.org/licenses/>.
21 import sigrokdecode as srd
23 class SamplerateError(Exception):
26 class Decoder(srd.Decoder):
30 longname = 'Pulse-width modulation'
31 desc = 'Analog level encoded in duty cycle percentage.'
36 {'id': 'data', 'name': 'Data', 'desc': 'Data line'},
39 {'id': 'polarity', 'desc': 'Polarity', 'default': 'active-high',
40 'values': ('active-low', 'active-high')},
43 ('duty-cycle', 'Duty cycle'),
47 ('duty-cycle', 'Duty cycle', (0,)),
48 ('period', 'Period', (1,)),
58 self.samplerate = None
59 self.ss_block = self.es_block = None
61 def metadata(self, key, value):
62 if key == srd.SRD_CONF_SAMPLERATE:
63 self.samplerate = value
66 self.out_ann = self.register(srd.OUTPUT_ANN)
67 self.out_binary = self.register(srd.OUTPUT_BINARY)
69 self.register(srd.OUTPUT_META,
70 meta=(float, 'Average', 'PWM base (cycle) frequency'))
73 self.put(self.ss_block, self.es_block, self.out_ann, data)
75 def putp(self, period_t):
77 if period_t == 0 or period_t >= 1:
78 period_s = '%.1f s' % (period_t)
79 elif period_t <= 1e-12:
80 period_s = '%.1f fs' % (period_t * 1e15)
81 elif period_t <= 1e-9:
82 period_s = '%.1f ps' % (period_t * 1e12)
83 elif period_t <= 1e-6:
84 period_s = '%.1f ns' % (period_t * 1e9)
85 elif period_t <= 1e-3:
86 period_s = '%.1f μs' % (period_t * 1e6)
88 period_s = '%.1f ms' % (period_t * 1e3)
90 self.put(self.ss_block, self.es_block, self.out_ann, [1, [period_s]])
93 self.put(self.ss_block, self.es_block, self.out_binary, data)
96 if not self.samplerate:
97 raise SamplerateError('Cannot decode without samplerate.')
102 # Wait for an "active" edge (depends on config). This starts
103 # the first full period of the inspected signal waveform.
104 self.wait({0: 'f' if self.options['polarity'] == 'active-low' else 'r'})
105 self.first_samplenum = self.samplenum
107 # Keep getting samples for the period's middle and terminal edges.
108 # At the same time that last sample starts the next period.
111 # Get the next two edges. Setup some variables that get
112 # referenced in the calculation and in put() routines.
113 start_samplenum = self.samplenum
115 end_samplenum = self.samplenum
117 self.ss_block = start_samplenum
118 self.es_block = self.samplenum
120 # Calculate the period, the duty cycle, and its ratio.
121 period = self.samplenum - start_samplenum
122 duty = end_samplenum - start_samplenum
123 ratio = float(duty / period)
125 # Report the duty cycle in percent.
126 percent = float(ratio * 100)
127 self.putx([0, ['%f%%' % percent]])
129 # Report the duty cycle in the binary output.
130 self.putb([0, bytes([int(ratio * 256)])])
132 # Report the period in units of time.
133 period_t = float(period / self.samplerate)
136 # Update and report the new duty cycle average.
139 self.put(self.first_samplenum, self.es_block, self.out_average,
140 float(average / num_cycles))