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1 | ## |
2 | ## This file is part of the sigrok project. | |
3 | ## | |
4 | ## Copyright (C) 2012 Bert Vermeulen <bert@biot.com> | |
5 | ## | |
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 3 of the License, or | |
9 | ## (at your option) any later version. | |
10 | ## | |
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. | |
15 | ## | |
16 | ## You should have received a copy of the GNU General Public License | |
17 | ## along with this program; if not, If not, see <http://www.gnu.org/licenses/>. | |
18 | ## | |
19 | ||
20 | # | |
21 | # DDC protocol decoder | |
22 | # | |
23 | # This decoder extracts a DDC stream from an I2C session between a computer | |
24 | # and a display device. The stream is output as plain bytes. | |
25 | # | |
26 | ||
27 | import sigrokdecode | |
28 | ||
29 | ||
30 | class Decoder(sigrokdecode.Decoder): | |
31 | id = 'ddc' | |
32 | name = 'DDC' | |
33 | longname = 'Display Data Channel' | |
34 | desc = 'DDC is a protocol for communication between computers and displays.' | |
35 | longdesc = '' | |
36 | author = 'Bert Vermeulen <bert@biot.com>' | |
37 | license = 'gplv3+' | |
38 | inputs = ['i2c'] | |
39 | outputs = ['ddc'] | |
40 | annotation = [ | |
41 | ["Byte stream", "DDC byte stream as read from display."], | |
42 | ] | |
43 | ||
44 | def __init__(self, **kwargs): | |
45 | self.state = None | |
46 | ||
47 | def start(self, metadata): | |
c9b24fc3 | 48 | self.out_ann = self.add(sigrokdecode.SRD_OUTPUT_ANNOTATION, 'ddc') |
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49 | |
50 | def decode(self, start_sample, end_sample, i2c_data): | |
51 | try: | |
52 | cmd, data, ack_bit = i2c_data | |
53 | except Exception as e: | |
54 | raise Exception("malformed I2C input: %s" % str(e)) from e | |
55 | ||
56 | if self.state is None: | |
57 | # waiting for the DDC session to start | |
58 | if cmd in ('START', 'START_REPEAT'): | |
59 | self.state = 'start' | |
60 | elif self.state == 'start': | |
61 | if cmd == 'ADDRESS_READ' and data == 80: | |
62 | # 80 is the I2C slave address of a connected display, | |
63 | # so this marks the start of the DDC data transfer. | |
64 | self.state = 'transfer' | |
65 | elif cmd == 'STOP': | |
66 | # back to idle | |
67 | self.state = None | |
68 | elif self.state == 'transfer': | |
69 | if cmd == 'DATA_READ': | |
70 | # there shouldn't be anything but data reads on this | |
71 | # address, so ignore everything else | |
c9b24fc3 | 72 | self.put(start_sample, end_sample, self.out_ann, |
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73 | [0, ["0x%.2x" % data]]) |
74 |