2 ## This file is part of the libsigrokdecode project.
4 ## Copyright (C) 2012 Joel Holdsworth <joel@airwebreathe.org.uk>
6 ## This program is free software; you can redistribute it and/or modify
7 ## it under the terms of the GNU General Public License as published by
8 ## the Free Software Foundation; either version 2 of the License, or
9 ## (at your option) any later version.
11 ## This program is distributed in the hope that it will be useful,
12 ## but WITHOUT ANY WARRANTY; without even the implied warranty of
13 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 ## GNU General Public License for more details.
16 ## You should have received a copy of the GNU General Public License
17 ## along with this program; if not, write to the Free Software
18 ## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
21 # I²S protocol decoder
23 import sigrokdecode as srd
26 Protocol output format:
32 - 'DATA', [<channel>, <value>]
38 class Decoder(srd.Decoder):
42 longname = 'Integrated Interchip Sound'
43 desc = 'Serial bus for connecting digital audio devices.'
48 {'id': 'sck', 'name': 'SCK', 'desc': 'Bit clock line'},
49 {'id': 'ws', 'name': 'WS', 'desc': 'Word select line'},
50 {'id': 'sd', 'name': 'SD', 'desc': 'Serial data line'},
55 ['left', 'Left channel'],
56 ['right', 'Right channel'],
57 ['warnings', 'Warnings'],
60 def __init__(self, **kwargs):
61 self.samplerate = None
66 self.samplesreceived = 0
67 self.first_sample = None
68 self.start_sample = None
72 self.out_proto = self.register(srd.OUTPUT_PYTHON)
73 self.out_ann = self.register(srd.OUTPUT_ANN)
75 def metadata(self, key, value):
76 if key == srd.SRD_CONF_SAMPLERATE:
77 self.samplerate = value
79 def putpb(self, data):
80 self.put(self.start_sample, self.samplenum, self.out_proto, data)
83 self.put(self.start_sample, self.samplenum, self.out_ann, data)
87 # Calculate the sample rate.
89 if self.start_sample != None and \
90 self.first_sample != None and \
91 self.start_sample > self.first_sample:
92 samplerate = '%d' % (self.samplesreceived *
93 self.samplerate / (self.start_sample -
96 return 'I²S: %d %d-bit samples received at %sHz' % \
97 (self.samplesreceived, self.wordlength, samplerate)
99 def decode(self, ss, es, data):
100 if self.samplerate is None:
101 raise Exception("Cannot decode without samplerate.")
102 for self.samplenum, (sck, ws, sd) in data:
104 # Ignore sample if the bit clock hasn't changed.
105 if sck == self.oldsck:
109 if sck == 0: # Ignore the falling clock edge.
112 self.data = (self.data << 1) | sd
115 # This was not the LSB unless WS has flipped.
119 # Only submit the sample, if we received the beginning of it.
120 if self.start_sample != None:
121 self.samplesreceived += 1
123 idx = 0 if self.oldws else 1
124 c1 = 'Left channel' if self.oldws else 'Right channel'
125 c2 = 'Left' if self.oldws else 'Right'
126 c3 = 'L' if self.oldws else 'R'
127 v = '%08x' % self.data
128 self.putpb(['DATA', [c3, self.data]])
129 self.putb([idx, ['%s: %s' % (c1, v), '%s: %s' % (c2, v),
130 '%s: %s' % (c3, v), c3]])
132 # Check that the data word was the correct length.
133 if self.wordlength != -1 and self.wordlength != self.bitcount:
134 self.putb([2, ['Received %d-bit word, expected %d-bit '
135 'word' % (self.bitcount, self.wordlength)]])
137 self.wordlength = self.bitcount
139 # Reset decoder state.
142 self.start_sample = self.samplenum
144 # Save the first sample position.
145 if self.first_sample == None:
146 self.first_sample = self.samplenum