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):
65 self.samplesreceived = 0
66 self.first_sample = None
67 self.start_sample = None
70 def start(self, metadata):
71 self.samplerate = metadata['samplerate']
72 self.out_proto = self.add(srd.OUTPUT_PROTO, 'i2s')
73 self.out_ann = self.add(srd.OUTPUT_ANN, 'i2s')
75 def putpb(self, data):
76 self.put(self.start_sample, self.samplenum, self.out_proto, data)
79 self.put(self.start_sample, self.samplenum, self.out_ann, data)
83 # Calculate the sample rate.
85 if self.start_sample != None and \
86 self.first_sample != None and \
87 self.start_sample > self.first_sample:
88 samplerate = '%d' % (self.samplesreceived *
89 self.samplerate / (self.start_sample -
92 return 'I2S: %d %d-bit samples received at %sHz' % \
93 (self.samplesreceived, self.wordlength, samplerate)
95 def decode(self, ss, es, data):
96 for self.samplenum, (sck, ws, sd) in data:
98 # Ignore sample if the bit clock hasn't changed.
99 if sck == self.oldsck:
103 if sck == 0: # Ignore the falling clock edge.
106 self.data = (self.data << 1) | sd
109 # This was not the LSB unless WS has flipped.
113 # Only submit the sample, if we received the beginning of it.
114 if self.start_sample != None:
115 self.samplesreceived += 1
116 self.putpb(['DATA', ['L' if self.oldws else 'R', self.data]])
117 self.putb([0 if self.oldws else 1, ['0x%08x' % self.data]])
119 # Check that the data word was the correct length.
120 if self.wordlength != -1 and self.wordlength != self.bitcount:
121 self.putb([2, ['Received %d-bit word, expected %d-bit '
122 'word' % (self.bitcount, self.wordlength)]])
124 self.wordlength = self.bitcount
126 # Reset decoder state.
129 self.start_sample = self.samplenum
131 # Save the first sample position.
132 if self.first_sample == None:
133 self.first_sample = self.samplenum