decoders/i2cdemux/pd.py

   1 ##
   2 ## This file is part of the libsigrokdecode project.
   3 ##
   4 ## Copyright (C) 2012 Uwe Hermann <uwe@hermann-uwe.de>
   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 2 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, see <http://www.gnu.org/licenses/>.
  18 ##
  19
  20 import sigrokdecode as srd
  21
  22 class Decoder(srd.Decoder):
  23     api_version = 3
  24     id = 'i2cdemux'
  25     name = 'I²C demux'
  26     longname = 'I²C demultiplexer'
  27     desc = 'Demux I²C packets into per-slave-address streams.'
  28     license = 'gplv2+'
  29     inputs = ['i2c']
  30     outputs = [] # TODO: Only known at run-time.
  31     tags = ['Util']
  32
  33     def __init__(self):
  34         self.reset()
  35
  36     def reset(self):
  37         self.packets = [] # Local cache of I²C packets
  38         self.slaves = [] # List of known slave addresses
  39         self.stream = -1 # Current output stream
  40         self.streamcount = 0 # Number of created output streams
  41
  42     def start(self):
  43         self.out_python = []
  44
  45     # Grab I²C packets into a local cache, until an I²C STOP condition
  46     # packet comes along. At some point before that STOP condition, there
  47     # will have been an ADDRESS READ or ADDRESS WRITE which contains the
  48     # I²C address of the slave that the master wants to talk to.
  49     # We use this slave address to figure out which output stream should
  50     # get the whole chunk of packets (from START to STOP).
  51     def decode(self, ss, es, data):
  52
  53         cmd, databyte = data
  54
  55         # Add the I²C packet to our local cache.
  56         self.packets.append([ss, es, data])
  57
  58         if cmd in ('ADDRESS READ', 'ADDRESS WRITE'):
  59             if databyte in self.slaves:
  60                 self.stream = self.slaves.index(databyte)
  61                 return
  62
  63             # We're never seen this slave, add a new stream.
  64             self.slaves.append(databyte)
  65             self.out_python.append(self.register(srd.OUTPUT_PYTHON,
  66                                    proto_id='i2c-%s' % hex(databyte)))
  67             self.stream = self.streamcount
  68             self.streamcount += 1
  69         elif cmd == 'STOP':
  70             if self.stream == -1:
  71                 raise Exception('Invalid stream!') # FIXME?
  72
  73             # Send the whole chunk of I²C packets to the correct stream.
  74             for p in self.packets:
  75                 self.put(p[0], p[1], self.out_python[self.stream], p[2])
  76
  77             self.packets = []
  78             self.stream = -1
  79         else:
  80             pass # Do nothing, only add the I²C packet to our cache.