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##
## 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, see <http://www.gnu.org/licenses/>.
##
# Generic I2C filtering protocol decoder
import sigrokdecode as srd
class Decoder(srd.Decoder):
api_version = 1
id = 'i2cfilter'
name = 'I2C filter'
longname = 'I2C filter'
desc = 'Filter out specific addresses/directions in an I2C stream.'
license = 'gplv3+'
inputs = ['i2c']
outputs = []
options = {
'address': ['Address to filter out of the I2C stream', 0],
'direction': ['Direction to filter (read/write)', '']
}
def __init__(self, **kwargs):
self.state = None
def start(self, metadata):
self.out_proto = self.add(srd.OUTPUT_PROTO, 'i2cdata')
if self.options['direction'] not in ('', 'read', 'write'):
raise Exception('Invalid direction: expected "read" or "write"')
def decode(self, ss, es, data):
try:
cmd, data = data
except Exception as e:
raise Exception('Malformed I2C input: %s' % str(e)) from e
# Whichever state we're in, these always reset the state machine.
# This should make it easier to deal with corrupt data etc.
if cmd in ('START', 'START REPEAT'):
self.state = 'start'
return
if cmd == 'STOP':
self.state = None
return
if cmd in ('ACK', 'NACK'):
# Don't care, we just want data.
return
if self.state == 'start':
# Start of a transfer, see if we want this one.
if cmd == 'ADDRESS READ' and self.options['direction'] == 'write':
return
elif cmd == 'ADDRESS WRITE' and self.options['direction'] == 'read':
return
elif cmd in ('ADDRESS READ', 'ADDRESS WRITE'):
if self.options['address'] in (0, data):
# We want this tranfer.
self.state = 'transfer'
elif self.state == 'transfer':
if cmd in ('DATA READ', 'DATA WRITE'):
self.put(ss, es, self.out_proto, data)
else:
raise Exception('Invalid state: %s' % self.state)
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