+++ /dev/null
-##
-## 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
-#
-
-#
-# The Inter-Integrated Circuit (I2C) bus is a bidirectional, multi-master
-# bus using two signals (SCL = serial clock line, SDA = serial data line).
-#
-# There can be many devices on the same bus. Each device can potentially be
-# master or slave (and that can change during runtime). Both slave and master
-# can potentially play the transmitter or receiver role (this can also
-# change at runtime).
-#
-# Possible maximum data rates:
-# - Standard mode: 100 kbit/s
-# - Fast mode: 400 kbit/s
-# - Fast-mode Plus: 1 Mbit/s
-# - High-speed mode: 3.4 Mbit/s
-#
-# START condition (S): SDA = falling, SCL = high
-# Repeated START condition (Sr): same as S
-# Data bit sampling: SCL = rising
-# STOP condition (P): SDA = rising, SCL = high
-#
-# All data bytes on SDA are exactly 8 bits long (transmitted MSB-first).
-# Each byte has to be followed by a 9th ACK/NACK bit. If that bit is low,
-# that indicates an ACK, if it's high that indicates a NACK.
-#
-# After the first START condition, a master sends the device address of the
-# slave it wants to talk to. Slave addresses are 7 bits long (MSB-first).
-# After those 7 bits, a data direction bit is sent. If the bit is low that
-# indicates a WRITE operation, if it's high that indicates a READ operation.
-#
-# Later an optional 10bit slave addressing scheme was added.
-#
-# Documentation:
-# http://www.nxp.com/acrobat/literature/9398/39340011.pdf (v2.1 spec)
-# http://www.nxp.com/acrobat/usermanuals/UM10204_3.pdf (v3 spec)
-# http://en.wikipedia.org/wiki/I2C
-#
-
-# 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.
-
-'''
-Protocol output format:
-
-I2C packet:
-[<i2c_command>, <data>, <ack_bit>]
-
-<i2c_command> is one of:
- - 'START' (START condition)
- - 'START REPEAT' (Repeated START)
- - 'ADDRESS READ' (Address, read)
- - 'ADDRESS WRITE' (Address, write)
- - 'DATA READ' (Data, read)
- - 'DATA WRITE' (Data, write)
- - 'STOP' (STOP condition)
-
-<data> is the data or address byte associated with the 'ADDRESS*' and 'DATA*'
-command. For 'START', 'START REPEAT' and 'STOP', this is None.
-
-<ack_bit> is either 'ACK' or 'NACK', but may also be None.
-'''
-
-import sigrokdecode as srd
-
-# Annotation feed formats
-ANN_SHIFTED = 0
-ANN_SHIFTED_SHORT = 1
-ANN_RAW = 2
-
-# Values are verbose and short annotation, respectively.
-protocol = {
- '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'],
-}
-
-# States
-FIND_START = 0
-FIND_ADDRESS = 1
-FIND_DATA = 2
-
-class Decoder(srd.Decoder):
- id = 'i2c'
- name = 'I2C'
- longname = 'Inter-Integrated Circuit'
- desc = 'I2C is a two-wire, multi-master, serial bus.'
- longdesc = '...'
- license = 'gplv2+'
- inputs = ['logic']
- outputs = ['i2c']
- probes = [
- {'id': 'scl', 'name': 'SCL', 'desc': 'Serial clock line'},
- {'id': 'sda', 'name': 'SDA', 'desc': 'Serial data line'},
- ]
- 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.samplecnt = 0
- self.bitcount = 0
- self.databyte = 0
- self.wr = -1
- self.startsample = -1
- self.is_repeat_start = 0
- self.state = FIND_START
- self.oldscl = None
- self.oldsda = None
-
- # Set protocol decoder option defaults.
- self.addressing = Decoder.options['addressing'][1]
-
- 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):
- cmd = 'START REPEAT' if (self.is_repeat_start == 1) else 'START'
-
- self.put(self.out_proto, [cmd, None, None])
- self.put(self.out_ann, [ANN_SHIFTED, [protocol[cmd][0]]])
- self.put(self.out_ann, [ANN_SHIFTED_SHORT, [protocol[cmd][1]]])
-
- self.state = FIND_ADDRESS
- self.bitcount = self.databyte = 0
- self.is_repeat_start = 1
- self.wr = -1
-
- def found_address_or_data(self, scl, sda):
- # Gather 8 bits of data plus the ACK/NACK bit.
-
- if self.startsample == -1:
- # TODO: Should be samplenum, as received from the feed.
- self.startsample = self.samplecnt
- self.bitcount += 1
-
- # Address and data are transmitted MSB-first.
- self.databyte <<= 1
- self.databyte |= sda
-
- # Return if we haven't collected all 8 + 1 bits, yet.
- if self.bitcount != 9:
- return
-
- # 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]])
-
- # We received 8 address/data bits and the ACK/NACK bit.
- self.databyte >>= 1 # Shift out unwanted ACK/NACK bit here.
-
- 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
- else:
- # TODO: Error?
- pass
-
- # Last bit that came in was the ACK/NACK bit (1 = NACK).
- ack_bit = 'NACK' if (sda == 1) else 'ACK'
-
- 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, ack_bit])
- self.put(self.out_ann, [ANN_SHIFTED,
- [protocol[cmd][0], '0x%02x' % d, protocol[ack_bit][0]]])
- self.put(self.out_ann, [ANN_SHIFTED_SHORT,
- [protocol[cmd][1], '0x%02x' % d, protocol[ack_bit][1]]])
-
- self.bitcount = self.databyte = 0
- self.startsample = -1
-
- if self.state == FIND_ADDRESS:
- self.state = FIND_DATA
- elif self.state == FIND_DATA:
- # There could be multiple data bytes in a row.
- # So, either find a STOP condition or another data byte next.
- pass
-
- def found_stop(self, scl, sda):
- self.put(self.out_proto, ['STOP', None, None])
- self.put(self.out_ann, [ANN_SHIFTED, [protocol['STOP'][0]]])
- self.put(self.out_ann, [ANN_SHIFTED_SHORT, [protocol['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.
- # TODO: 0-0 sample range for now.
- super(Decoder, self).put(0, 0, output_id, data)
-
- def decode(self, ss, es, data):
- for samplenum, (scl, sda) in data:
- self.samplecnt += 1
-
- # 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)
- else:
- # TODO: Error?
- pass
-
- # Save current SDA/SCL values for the next round.
- self.oldscl = scl
- self.oldsda = sda
-
projects / libsigrokdecode.git / blobdiff