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7ce7775c BV |
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 | ## | |
87998e97 BV |
19 | """ |
20 | This decoder extracts a DDC stream from an I2C session between a computer | |
21 | and a display device. The stream is output as plain bytes. | |
7ce7775c | 22 | |
87998e97 BV |
23 | Details: |
24 | https://en.wikipedia.org/wiki/Display_Data_Channel | |
25 | """ | |
7ce7775c | 26 | |
677d597b | 27 | import sigrokdecode as srd |
7ce7775c | 28 | |
677d597b | 29 | class Decoder(srd.Decoder): |
7ce7775c BV |
30 | id = 'ddc' |
31 | name = 'DDC' | |
32 | longname = 'Display Data Channel' | |
eb7082c9 | 33 | desc = 'A protocol for communication between computers and displays.' |
7ce7775c | 34 | longdesc = '' |
526e5804 UH |
35 | author = 'Bert Vermeulen' |
36 | email = 'bert@biot.com' | |
7ce7775c BV |
37 | license = 'gplv3+' |
38 | inputs = ['i2c'] | |
39 | outputs = ['ddc'] | |
9a12a6e7 UH |
40 | probes = [] |
41 | options = {} | |
e97b6ef5 | 42 | annotations = [ |
eb7082c9 | 43 | ['Byte stream', 'DDC byte stream as read from display.'], |
7ce7775c BV |
44 | ] |
45 | ||
46 | def __init__(self, **kwargs): | |
47 | self.state = None | |
48 | ||
49 | def start(self, metadata): | |
56202222 | 50 | self.out_ann = self.add(srd.OUTPUT_ANN, 'ddc') |
7ce7775c | 51 | |
2b9837d9 | 52 | def decode(self, ss, es, data): |
7ce7775c | 53 | try: |
2b9837d9 | 54 | cmd, data, ack_bit = data |
7ce7775c | 55 | except Exception as e: |
eb7082c9 | 56 | raise Exception('malformed I2C input: %s' % str(e)) from e |
7ce7775c BV |
57 | |
58 | if self.state is None: | |
eb7082c9 | 59 | # Wait for the DDC session to start. |
a2d2aff2 | 60 | if cmd in ('START', 'START REPEAT'): |
7ce7775c BV |
61 | self.state = 'start' |
62 | elif self.state == 'start': | |
a2d2aff2 | 63 | if cmd == 'ADDRESS READ' and data == 80: |
7ce7775c BV |
64 | # 80 is the I2C slave address of a connected display, |
65 | # so this marks the start of the DDC data transfer. | |
66 | self.state = 'transfer' | |
67 | elif cmd == 'STOP': | |
eb7082c9 | 68 | # Got back to the idle state. |
7ce7775c BV |
69 | self.state = None |
70 | elif self.state == 'transfer': | |
a2d2aff2 | 71 | if cmd == 'DATA READ': |
eb7082c9 UH |
72 | # There shouldn't be anything but data reads on this |
73 | # address, so ignore everything else. | |
2b9837d9 | 74 | self.put(ss, es, self.out_ann, [0, ['0x%.2x' % data]]) |
7ce7775c | 75 |