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authorUwe Hermann <uwe@hermann-uwe.de>2012-11-21 22:43:02 +0100
committerUwe Hermann <uwe@hermann-uwe.de>2012-11-24 20:21:19 +0100
commit24c74fd30fb161837c5f8b01baf3c0fe2dfa4ed5 (patch)
tree43d0c24c6a18e824d9d66a390bad9cff3aa081af /decoders/i2c/i2c.py
parent23f999aa996e54cd73cb54d5e254d1445d65847d (diff)
downloadlibsigrokdecode-24c74fd30fb161837c5f8b01baf3c0fe2dfa4ed5.tar.gz
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All PDs: Name the files pd.py consistently.
The Python module name is determined by the directory name (e.g. dcf77), the *.py file names in that directory don't matter and can be kept consistent.
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-##
-## This file is part of the sigrok project.
-##
-## Copyright (C) 2010-2011 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 2 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, write to the Free Software
-## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
-##
-
-# I2C protocol decoder
-
-# TODO: Look into arbitration, collision detection, clock synchronisation, etc.
-# TODO: Handle clock stretching.
-# TODO: Handle combined messages / repeated START.
-# TODO: Implement support for 7bit and 10bit slave addresses.
-# TODO: Implement support for inverting SDA/SCL levels (0->1 and 1->0).
-# TODO: Implement support for detecting various bus errors.
-# TODO: I2C address of slaves.
-# TODO: Handle multiple different I2C devices on same bus
-# -> we need to decode multiple protocols at the same time.
-
-import sigrokdecode as srd
-
-# Annotation feed formats
-ANN_SHIFTED = 0
-ANN_SHIFTED_SHORT = 1
-ANN_RAW = 2
-
-# Values are verbose and short annotation, respectively.
-proto = {
- 'START': ['START', 'S'],
- 'START REPEAT': ['START REPEAT', 'Sr'],
- 'STOP': ['STOP', 'P'],
- 'ACK': ['ACK', 'A'],
- 'NACK': ['NACK', 'N'],
- 'ADDRESS READ': ['ADDRESS READ', 'AR'],
- 'ADDRESS WRITE': ['ADDRESS WRITE', 'AW'],
- 'DATA READ': ['DATA READ', 'DR'],
- 'DATA WRITE': ['DATA WRITE', 'DW'],
-}
-
-class Decoder(srd.Decoder):
- api_version = 1
- id = 'i2c'
- name = 'I2C'
- longname = 'Inter-Integrated Circuit'
- desc = 'Two-wire, multi-master, serial bus.'
- license = 'gplv2+'
- inputs = ['logic']
- outputs = ['i2c']
- probes = [
- {'id': 'scl', 'name': 'SCL', 'desc': 'Serial clock line'},
- {'id': 'sda', 'name': 'SDA', 'desc': 'Serial data line'},
- ]
- optional_probes = []
- options = {
- 'addressing': ['Slave addressing (in bits)', 7], # 7 or 10
- }
- annotations = [
- # ANN_SHIFTED
- ['7-bit shifted hex',
- 'Read/write bit shifted out from the 8-bit I2C slave address'],
- # ANN_SHIFTED_SHORT
- ['7-bit shifted hex (short)',
- 'Read/write bit shifted out from the 8-bit I2C slave address'],
- # ANN_RAW
- ['Raw hex', 'Unaltered raw data'],
- ]
-
- def __init__(self, **kwargs):
- self.startsample = -1
- self.samplenum = None
- self.bitcount = 0
- self.databyte = 0
- self.wr = -1
- self.is_repeat_start = 0
- self.state = 'FIND START'
- self.oldscl = None
- self.oldsda = None
- self.oldpins = None
-
- def start(self, metadata):
- self.out_proto = self.add(srd.OUTPUT_PROTO, 'i2c')
- self.out_ann = self.add(srd.OUTPUT_ANN, 'i2c')
-
- def report(self):
- pass
-
- def is_start_condition(self, scl, sda):
- # START condition (S): SDA = falling, SCL = high
- if (self.oldsda == 1 and sda == 0) and scl == 1:
- return True
- return False
-
- def is_data_bit(self, scl, sda):
- # Data sampling of receiver: SCL = rising
- if self.oldscl == 0 and scl == 1:
- return True
- return False
-
- def is_stop_condition(self, scl, sda):
- # STOP condition (P): SDA = rising, SCL = high
- if (self.oldsda == 0 and sda == 1) and scl == 1:
- return True
- return False
-
- def found_start(self, scl, sda):
- self.startsample = self.samplenum
-
- cmd = 'START REPEAT' if (self.is_repeat_start == 1) else 'START'
- self.put(self.out_proto, [cmd, None])
- self.put(self.out_ann, [ANN_SHIFTED, [proto[cmd][0]]])
- self.put(self.out_ann, [ANN_SHIFTED_SHORT, [proto[cmd][1]]])
-
- self.state = 'FIND ADDRESS'
- self.bitcount = self.databyte = 0
- self.is_repeat_start = 1
- self.wr = -1
-
- # Gather 8 bits of data plus the ACK/NACK bit.
- def found_address_or_data(self, scl, sda):
- # Address and data are transmitted MSB-first.
- self.databyte <<= 1
- self.databyte |= sda
-
- if self.bitcount == 0:
- self.startsample = self.samplenum
-
- # Return if we haven't collected all 8 + 1 bits, yet.
- self.bitcount += 1
- if self.bitcount != 8:
- return
-
- # We triggered on the ACK/NACK bit, but won't report that until later.
- self.startsample -= 1
-
- # Send raw output annotation before we start shifting out
- # read/write and ACK/NACK bits.
- self.put(self.out_ann, [ANN_RAW, ['0x%.2x' % self.databyte]])
-
- if self.state == 'FIND ADDRESS':
- # The READ/WRITE bit is only in address bytes, not data bytes.
- self.wr = 0 if (self.databyte & 1) else 1
- d = self.databyte >> 1
- elif self.state == 'FIND DATA':
- d = self.databyte
-
- if self.state == 'FIND ADDRESS' and self.wr == 1:
- cmd = 'ADDRESS WRITE'
- elif self.state == 'FIND ADDRESS' and self.wr == 0:
- cmd = 'ADDRESS READ'
- elif self.state == 'FIND DATA' and self.wr == 1:
- cmd = 'DATA WRITE'
- elif self.state == 'FIND DATA' and self.wr == 0:
- cmd = 'DATA READ'
-
- self.put(self.out_proto, [cmd, d])
- self.put(self.out_ann, [ANN_SHIFTED, [proto[cmd][0], '0x%02x' % d]])
- self.put(self.out_ann, [ANN_SHIFTED_SHORT, [proto[cmd][1], '0x%02x' % d]])
-
- # Done with this packet.
- self.startsample = -1
- self.bitcount = self.databyte = 0
- self.state = 'FIND ACK'
-
- def get_ack(self, scl, sda):
- self.startsample = self.samplenum
- ack_bit = 'NACK' if (sda == 1) else 'ACK'
- self.put(self.out_proto, [ack_bit, None])
- self.put(self.out_ann, [ANN_SHIFTED, [proto[ack_bit][0]]])
- self.put(self.out_ann, [ANN_SHIFTED_SHORT, [proto[ack_bit][1]]])
- # There could be multiple data bytes in a row, so either find
- # another data byte or a STOP condition next.
- self.state = 'FIND DATA'
-
- def found_stop(self, scl, sda):
- self.startsample = self.samplenum
- self.put(self.out_proto, ['STOP', None])
- self.put(self.out_ann, [ANN_SHIFTED, [proto['STOP'][0]]])
- self.put(self.out_ann, [ANN_SHIFTED_SHORT, [proto['STOP'][1]]])
-
- self.state = 'FIND START'
- self.is_repeat_start = 0
- self.wr = -1
-
- def put(self, output_id, data):
- # Inject sample range into the call up to sigrok.
- super(Decoder, self).put(self.startsample, self.samplenum, output_id, data)
-
- def decode(self, ss, es, data):
- for (self.samplenum, pins) in data:
-
- # Ignore identical samples early on (for performance reasons).
- if self.oldpins == pins:
- continue
- self.oldpins, (scl, sda) = pins, pins
-
- # First sample: Save SCL/SDA value.
- if self.oldscl == None:
- self.oldscl = scl
- self.oldsda = sda
- continue
-
- # TODO: Wait until the bus is idle (SDA = SCL = 1) first?
-
- # State machine.
- if self.state == 'FIND START':
- if self.is_start_condition(scl, sda):
- self.found_start(scl, sda)
- elif self.state == 'FIND ADDRESS':
- if self.is_data_bit(scl, sda):
- self.found_address_or_data(scl, sda)
- elif self.state == 'FIND DATA':
- if self.is_data_bit(scl, sda):
- self.found_address_or_data(scl, sda)
- elif self.is_start_condition(scl, sda):
- self.found_start(scl, sda)
- elif self.is_stop_condition(scl, sda):
- self.found_stop(scl, sda)
- elif self.state == 'FIND ACK':
- if self.is_data_bit(scl, sda):
- self.get_ack(scl, sda)
- else:
- raise Exception('Invalid state %d' % self.STATE)
-
- # Save current SDA/SCL values for the next round.
- self.oldscl = scl
- self.oldsda = sda
-