X-Git-Url: https://sigrok.org/gitweb/?p=libsigrokdecode.git;a=blobdiff_plain;f=decoders%2Fddc%2Fddc.py;fp=decoders%2Fddc%2Fddc.py;h=f83909323b8b2a70d6d894f6e0db1a2ef22d91d4;hp=0000000000000000000000000000000000000000;hb=64c29e28e0efa184319f7831b3eca18c7f73f7d0;hpb=d0a0ed032e0120140a28e93ac42753786bf0087b

diff --git a/decoders/ddc/ddc.py b/decoders/ddc/ddc.py
new file mode 100644
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+++ b/decoders/ddc/ddc.py
@@ -0,0 +1,74 @@
+##
+## This file is part of the sigrok project.
+##
+## Copyright (C) 2012 Bert Vermeulen <bert@biot.com>
+##
+## 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 3 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, If not, see <http://www.gnu.org/licenses/>.
+##
+
+'''
+This decoder extracts a DDC stream from an I2C session between a computer
+and a display device. The stream is output as plain bytes.
+
+Details:
+https://en.wikipedia.org/wiki/Display_Data_Channel
+'''
+
+import sigrokdecode as srd
+
+class Decoder(srd.Decoder):
+    id = 'ddc'
+    name = 'DDC'
+    longname = 'Display Data Channel'
+    desc = 'A protocol for communication between computers and displays.'
+    longdesc = ''
+    license = 'gplv3+'
+    inputs = ['i2c']
+    outputs = ['ddc']
+    probes = []
+    options = {}
+    annotations = [
+        ['Byte stream', 'DDC byte stream as read from display.'],
+    ]
+
+    def __init__(self, **kwargs):
+        self.state = None
+
+    def start(self, metadata):
+        self.out_ann = self.add(srd.OUTPUT_ANN, 'ddc')
+
+    def decode(self, ss, es, data):
+        try:
+            cmd, data, ack_bit = data
+        except Exception as e:
+            raise Exception('malformed I2C input: %s' % str(e)) from e
+
+        if self.state is None:
+            # Wait for the DDC session to start.
+            if cmd in ('START', 'START REPEAT'):
+                self.state = 'start'
+        elif self.state == 'start':
+            if cmd == 'ADDRESS READ' and data == 80:
+                # 80 is the I2C slave address of a connected display,
+                # so this marks the start of the DDC data transfer.
+                self.state = 'transfer'
+            elif cmd == 'STOP':
+                # Got back to the idle state.
+                self.state = None
+        elif self.state == 'transfer':
+            if cmd == 'DATA READ':
+                # There shouldn't be anything but data reads on this
+                # address, so ignore everything else.
+                self.put(ss, es, self.out_ann, [0, ['0x%.2x' % data]])
+