srd/i2s: Initial implementation

[libsigrokdecode.git] / decoders / i2s / i2s.py

diff --git a/decoders/i2s/i2s.py b/decoders/i2s/i2s.py
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+++ b/decoders/i2s/i2s.py
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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
+
+    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 %d-bits: 0x%08x' % ('L' if self.oldws else 'R',
+                    self.bitcount, self.data)]])
+
+            # Reset decoder state.
+            self.data = 0
+            self.bitcount = 0
+            self.start_sample = self.samplenum
+                
+            self.oldws = ws
+            
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