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1 | ## | |
2 | ## This file is part of the libsigrokdecode project. | |
3 | ## | |
4 | ## Copyright (C) 2014 Torsten Duwe <duwe@suse.de> | |
5 | ## Copyright (C) 2014 Sebastien Bourdelin <sebastien.bourdelin@savoirfairelinux.com> | |
6 | ## | |
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. | |
11 | ## | |
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. | |
16 | ## | |
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/>. | |
19 | ## | |
20 | ||
21 | import sigrokdecode as srd | |
22 | ||
23 | class SamplerateError(Exception): | |
24 | pass | |
25 | ||
26 | class Decoder(srd.Decoder): | |
27 | api_version = 3 | |
28 | id = 'pwm' | |
29 | name = 'PWM' | |
30 | longname = 'Pulse-width modulation' | |
31 | desc = 'Analog level encoded in duty cycle percentage.' | |
32 | license = 'gplv2+' | |
33 | inputs = ['logic'] | |
34 | outputs = ['pwm'] | |
35 | channels = ( | |
36 | {'id': 'data', 'name': 'Data', 'desc': 'Data line'}, | |
37 | ) | |
38 | options = ( | |
39 | {'id': 'polarity', 'desc': 'Polarity', 'default': 'active-high', | |
40 | 'values': ('active-low', 'active-high')}, | |
41 | ) | |
42 | annotations = ( | |
43 | ('duty-cycle', 'Duty cycle'), | |
44 | ('period', 'Period'), | |
45 | ) | |
46 | annotation_rows = ( | |
47 | ('duty-cycle', 'Duty cycle', (0,)), | |
48 | ('period', 'Period', (1,)), | |
49 | ) | |
50 | binary = ( | |
51 | ('raw', 'RAW file'), | |
52 | ) | |
53 | ||
54 | def __init__(self): | |
55 | self.reset() | |
56 | ||
57 | def reset(self): | |
58 | self.samplerate = None | |
59 | self.ss_block = self.es_block = None | |
60 | ||
61 | def metadata(self, key, value): | |
62 | if key == srd.SRD_CONF_SAMPLERATE: | |
63 | self.samplerate = value | |
64 | ||
65 | def start(self): | |
66 | self.out_ann = self.register(srd.OUTPUT_ANN) | |
67 | self.out_binary = self.register(srd.OUTPUT_BINARY) | |
68 | self.out_average = \ | |
69 | self.register(srd.OUTPUT_META, | |
70 | meta=(float, 'Average', 'PWM base (cycle) frequency')) | |
71 | ||
72 | def putx(self, data): | |
73 | self.put(self.ss_block, self.es_block, self.out_ann, data) | |
74 | ||
75 | def putp(self, period_t): | |
76 | # Adjust granularity. | |
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) | |
87 | else: | |
88 | period_s = '%.1f ms' % (period_t * 1e3) | |
89 | ||
90 | self.put(self.ss_block, self.es_block, self.out_ann, [1, [period_s]]) | |
91 | ||
92 | def putb(self, data): | |
93 | self.put(self.ss_block, self.es_block, self.out_binary, data) | |
94 | ||
95 | def decode(self): | |
96 | if not self.samplerate: | |
97 | raise SamplerateError('Cannot decode without samplerate.') | |
98 | ||
99 | num_cycles = 0 | |
100 | average = 0 | |
101 | ||
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 | |
106 | ||
107 | # Keep getting samples for the period's middle and terminal edges. | |
108 | # At the same time that last sample starts the next period. | |
109 | while True: | |
110 | ||
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 | |
114 | self.wait({0: 'e'}) | |
115 | end_samplenum = self.samplenum | |
116 | self.wait({0: 'e'}) | |
117 | self.ss_block = start_samplenum | |
118 | self.es_block = self.samplenum | |
119 | ||
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) | |
124 | ||
125 | # Report the duty cycle in percent. | |
126 | percent = float(ratio * 100) | |
127 | self.putx([0, ['%f%%' % percent]]) | |
128 | ||
129 | # Report the duty cycle in the binary output. | |
130 | self.putb([0, bytes([int(ratio * 256)])]) | |
131 | ||
132 | # Report the period in units of time. | |
133 | period_t = float(period / self.samplerate) | |
134 | self.putp(period_t) | |
135 | ||
136 | # Update and report the new duty cycle average. | |
137 | num_cycles += 1 | |
138 | average += percent | |
139 | self.put(self.first_samplenum, self.es_block, self.out_average, | |
140 | float(average / num_cycles)) |