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
25 class Decoder(srd.Decoder):
29 longname = 'Integrated Interchip Sound'
30 desc = 'Serial bus for connecting digital audio devices.'
35 {'id': 'sck', 'name': 'SCK', 'desc': 'Bit clock line'},
36 {'id': 'ws', 'name': 'WS', 'desc': 'Word select line'},
37 {'id': 'sd', 'name': 'SD', 'desc': 'Serial data line'},
42 ['left', 'Left channel'],
43 ['right', 'Right channel'],
44 ['warnings', 'Warnings'],
47 def __init__(self, **kwargs):
52 self.samplesreceived = 0
53 self.first_sample = None
54 self.start_sample = None
57 def start(self, metadata):
58 self.samplerate = metadata['samplerate']
59 self.out_proto = self.add(srd.OUTPUT_PROTO, 'i2s')
60 self.out_ann = self.add(srd.OUTPUT_ANN, 'i2s')
64 # Calculate the sample rate.
66 if self.start_sample != None and \
67 self.first_sample != None and \
68 self.start_sample > self.first_sample:
69 samplerate = '%d' % (self.samplesreceived *
70 self.samplerate / (self.start_sample -
73 return 'I2S: %d %d-bit samples received at %sHz' % \
74 (self.samplesreceived, self.wordlength, samplerate)
76 def decode(self, ss, es, data):
77 for samplenum, (sck, ws, sd) in data:
79 # Ignore sample if the bit clock hasn't changed.
80 if sck == self.oldsck:
84 if sck == 0: # Ignore the falling clock edge.
87 self.data = (self.data << 1) | sd
90 # This was not the LSB unless WS has flipped.
94 # Only submit the sample, if we received the beginning of it.
95 if self.start_sample != None:
96 self.samplesreceived += 1
97 self.put(self.start_sample, samplenum, self.out_proto,
99 idx = 0 if self.oldws else 1
100 self.put(self.start_sample, samplenum, self.out_ann,
101 [idx, ['0x%08x', self.data)]])
103 # Check that the data word was the correct length.
104 if self.wordlength != -1 and self.wordlength != self.bitcount:
105 self.put(self.start_sample, samplenum, self.out_ann,
106 [2, ['Received a %d-bit word, when a '
107 '%d-bit word was expected' % (self.bitcount,
110 self.wordlength = self.bitcount
112 # Reset decoder state.
115 self.start_sample = samplenum
117 # Save the first sample position.
118 if self.first_sample == None:
119 self.first_sample = samplenum