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##
## This file is part of the sigrok project.
##
## Copyright (C) 2012 Joel Holdsworth <joel@airwebreathe.org.uk>
##
## This program is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 2 of the License, or
## (at your option) any later version.
##
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with this program; if not, write to the Free Software
## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
##
# I2S protocol decoder
import sigrokdecode as srd
# Annotation formats
ANN_HEX = 0
class Decoder(srd.Decoder):
api_version = 1
id = 'i2s'
name = 'I2S'
longname = 'Integrated Interchip Sound'
desc = 'I2S is an electrical serial bus interface standard used ' \
'for connecting digital audio devices together.'
license = 'gplv2+'
inputs = ['logic']
outputs = ['i2s']
probes = [
{'id': 'sck', 'name': 'SCK', 'desc': 'Bit clock line'},
{'id': 'ws', 'name': 'WS', 'desc': 'Word select line'},
{'id': 'sd', 'name': 'SD', 'desc': 'Serial Data line'},
]
annotations = [
['ASCII', 'Annotations in ASCII format'],
]
def __init__(self, **kwargs):
self.oldsck = 1
self.oldws = 1
self.bitcount = 0
self.data = 0
self.samplesreceived = 0
self.start_sample = None
self.samplenum = -1
self.wordlength = -1
def start(self, metadata):
self.out_proto = self.add(srd.OUTPUT_PROTO, 'i2s')
self.out_ann = self.add(srd.OUTPUT_ANN, 'i2s')
def report(self):
return 'I2S: %d samples received' % self.samplesreceived
def decode(self, ss, es, data):
for samplenum, (sck, ws, sd) in data:
# Ignore sample if the bit clock hasn't changed.
if sck == self.oldsck:
continue
self.oldsck = sck
if sck == 0: # Ignore the falling clock edge
continue
self.data = (self.data << 1) | sd
self.bitcount += 1
# This was not the LSB unless WS has flipped
if ws == self.oldws:
continue
# Only submit the sample, if we received the beginning of it
if self.start_sample != None:
self.samplesreceived += 1
self.put(self.start_sample, self.samplenum, self.out_proto,
['data', self.data])
self.put(self.start_sample, self.samplenum, self.out_ann,
[ANN_HEX, ['%s: 0x%08x' % ('L' if self.oldws else 'R',
self.data)]])
# Check that the data word was the correct length
if self.wordlength != -1 and self.wordlength != self.bitcount:
self.put(self.start_sample, self.samplenum, self.out_ann,
[ANN_HEX, ['WARNING: Received a %d-bit word, when a '
'%d-bit word was expected' % (self.bitcount,
self.wordlength)]])
self.wordlength = self.bitcount
# Reset decoder state.
self.data = 0
self.bitcount = 0
self.start_sample = self.samplenum
self.oldws = ws
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