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##
## This file is part of the libsigrokdecode project.
##
## Copyright (C) 2012 Bert Vermeulen <bert@biot.com>
## Copyright (C) 2012 Uwe Hermann <uwe@hermann-uwe.de>
##
## 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/>.
##
# TODO
# - Accept other slave address forms than decimal numbers?
# - Support for filtering out multiple slave/direction pairs?
# - Support 10bit slave addresses?
import copy
import sigrokdecode as srd
class Decoder(srd.Decoder):
api_version = 3
id = 'i2cfilter'
name = 'I²C filter'
longname = 'I²C filter'
desc = 'Filter out addresses/directions in an I²C stream.'
license = 'gplv3+'
inputs = ['i2c']
outputs = ['i2c']
tags = ['Util']
options = (
{'id': 'address', 'desc': 'Slave address to filter (decimal)',
'default': 0},
{'id': 'direction', 'desc': 'Direction to filter', 'default': 'both',
'values': ('read', 'write', 'both')}
)
def __init__(self):
self.reset()
def reset(self):
self.seen_packets = []
self.do_forward = None
def start(self):
self.out_python = self.register(srd.OUTPUT_PYTHON, proto_id='i2c')
if self.options['address'] not in range(0, 127 + 1):
raise Exception('Invalid slave (must be 0..127).')
self.want_addrs = []
if self.options['address']:
self.want_addrs.append(self.options['address'])
self.want_dir = {
'read': 'READ', 'write': 'WRITE',
}.get(self.options['direction'], None)
def _need_to_forward(self, slave_addr, direction):
if self.want_addrs and slave_addr not in self.want_addrs:
return False
if self.want_dir and direction != self.want_dir:
return False
return True
# Accumulate observed I2C packets until a STOP or REPEATED START
# condition is seen. These are conditions where transfers end or
# where direction potentially changes. Forward all previously
# accumulated traffic if it passes the slave address and direction
# filter. This assumes that the slave address as well as the read
# or write direction was part of the observed traffic. There should
# be no surprise when incomplete traffic does not match the filter
# condition.
def decode(self, ss, es, data):
# Unconditionally accumulate every lower layer packet we see.
# Keep deep copies for later, only reference caller's values
# as long as this .decode() invocation executes.
self.seen_packets.append([ss, es, copy.deepcopy(data)])
cmd, _ = data
# Check the slave address and transfer direction early when
# we see them. Keep accumulating packets while it's already
# known here whether to forward them. This simplifies other
# code paths. Including future handling of 10bit addresses.
if cmd in ('ADDRESS READ', 'ADDRESS WRITE'):
direction = cmd[len('ADDRESS '):]
_, slave_addr = data
self.do_forward = self._need_to_forward(slave_addr, direction)
return
# Forward previously accumulated packets as we see their
# completion, and when they pass the filter condition. Prepare
# to handle the next transfer (the next read/write part of it).
if cmd in ('STOP', 'START REPEAT'):
if self.do_forward:
for ss, es, data in self.seen_packets:
self.put(ss, es, self.out_python, data)
self.seen_packets.clear()
self.do_forward = None
return
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