[libsigrokdecode.git] / decoders / ddc.py

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