[libsigrokdecode.git] / decoders / i2c.py

##
## 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.

#
# I2C protocol output format:
#
# The protocol output consists of a (Python) list of I2C "packets", each of
# which is of the form
#
#        [<i2c_command>, <data>, <ack_bit>]
#
# <i2c_command> is one of:
#   - 'START' (START condition)
#   - 'START_REPEAT' (Repeated START)
#   - 'ADDRESS_READ' (Slave address, read)
#   - 'ADDRESS_WRITE' (Slave 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 = '...'
    author = 'Uwe Hermann'
    email = 'uwe@hermann-uwe.de'
    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
Commit	Line	Data
	1	##
	2	## This file is part of the sigrok project.
	3	##
	4	## Copyright (C) 2010-2011 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, write to the Free Software
	18	## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
	19	##
	20
	21	#
	22	# I2C protocol decoder
	23	#
	24
	25	#
	26	# The Inter-Integrated Circuit (I2C) bus is a bidirectional, multi-master
	27	# bus using two signals (SCL = serial clock line, SDA = serial data line).
	28	#
	29	# There can be many devices on the same bus. Each device can potentially be
	30	# master or slave (and that can change during runtime). Both slave and master
	31	# can potentially play the transmitter or receiver role (this can also
	32	# change at runtime).
	33	#
	34	# Possible maximum data rates:
	35	# - Standard mode: 100 kbit/s
	36	# - Fast mode: 400 kbit/s
	37	# - Fast-mode Plus: 1 Mbit/s
	38	# - High-speed mode: 3.4 Mbit/s
	39	#
	40	# START condition (S): SDA = falling, SCL = high
	41	# Repeated START condition (Sr): same as S
	42	# Data bit sampling: SCL = rising
	43	# STOP condition (P): SDA = rising, SCL = high
	44	#
	45	# All data bytes on SDA are exactly 8 bits long (transmitted MSB-first).
	46	# Each byte has to be followed by a 9th ACK/NACK bit. If that bit is low,
	47	# that indicates an ACK, if it's high that indicates a NACK.
	48	#
	49	# After the first START condition, a master sends the device address of the
	50	# slave it wants to talk to. Slave addresses are 7 bits long (MSB-first).
	51	# After those 7 bits, a data direction bit is sent. If the bit is low that
	52	# indicates a WRITE operation, if it's high that indicates a READ operation.
	53	#
	54	# Later an optional 10bit slave addressing scheme was added.
	55	#
	56	# Documentation:
	57	# http://www.nxp.com/acrobat/literature/9398/39340011.pdf (v2.1 spec)
	58	# http://www.nxp.com/acrobat/usermanuals/UM10204_3.pdf (v3 spec)
	59	# http://en.wikipedia.org/wiki/I2C
	60	#
	61
	62	# TODO: Look into arbitration, collision detection, clock synchronisation, etc.
	63	# TODO: Handle clock stretching.
	64	# TODO: Handle combined messages / repeated START.
	65	# TODO: Implement support for 7bit and 10bit slave addresses.
	66	# TODO: Implement support for inverting SDA/SCL levels (0->1 and 1->0).
	67	# TODO: Implement support for detecting various bus errors.
	68	# TODO: I2C address of slaves.
	69	# TODO: Handle multiple different I2C devices on same bus
	70	# -> we need to decode multiple protocols at the same time.
	71
	72	#
	73	# I2C protocol output format:
	74	#
	75	# The protocol output consists of a (Python) list of I2C "packets", each of
	76	# which is of the form
	77	#
	78	# [<i2c_command>, <data>, <ack_bit>]
	79	#
	80	# <i2c_command> is one of:
	81	# - 'START' (START condition)
	82	# - 'START_REPEAT' (Repeated START)
	83	# - 'ADDRESS_READ' (Slave address, read)
	84	# - 'ADDRESS_WRITE' (Slave address, write)
	85	# - 'DATA_READ' (Data, read)
	86	# - 'DATA_WRITE' (Data, write)
	87	# - 'STOP' (STOP condition)
	88	#
	89	# <data> is the data or address byte associated with the ADDRESS_* and DATA_*
	90	# command. For START, START_REPEAT and STOP, this is None.
	91	#
	92	# <ack_bit> is either 'ACK' or 'NACK', but may also be None.
	93	#
	94
	95	import sigrokdecode as srd
	96
	97	# Annotation feed formats
	98	ANN_SHIFTED = 0
	99	ANN_SHIFTED_SHORT = 1
	100	ANN_RAW = 2
	101
	102	# Values are verbose and short annotation, respectively.
	103	protocol = {
	104	'START': ['START', 'S'],
	105	'START_REPEAT': ['START REPEAT', 'Sr'],
	106	'STOP': ['STOP', 'P'],
	107	'ACK': ['ACK', 'A'],
	108	'NACK': ['NACK', 'N'],
	109	'ADDRESS_READ': ['ADDRESS READ', 'AR'],
	110	'ADDRESS_WRITE': ['ADDRESS WRITE', 'AW'],
	111	'DATA_READ': ['DATA READ', 'DR'],
	112	'DATA_WRITE': ['DATA WRITE', 'DW'],
	113	}
	114
	115	# States
	116	FIND_START = 0
	117	FIND_ADDRESS = 1
	118	FIND_DATA = 2
	119
	120	class Decoder(srd.Decoder):
	121	id = 'i2c'
	122	name = 'I2C'
	123	longname = 'Inter-Integrated Circuit'
	124	desc = 'I2C is a two-wire, multi-master, serial bus.'
	125	longdesc = '...'
	126	author = 'Uwe Hermann'
	127	email = 'uwe@hermann-uwe.de'
	128	license = 'gplv2+'
	129	inputs = ['logic']
	130	outputs = ['i2c']
	131	probes = [
	132	{'id': 'scl', 'name': 'SCL', 'desc': 'Serial clock line'},
	133	{'id': 'sda', 'name': 'SDA', 'desc': 'Serial data line'},
	134	]
	135	options = {
	136	'addressing': ['Slave addressing (in bits)', 7], # 7 or 10
	137	}
	138	annotations = [
	139	# ANN_SHIFTED
	140	['7-bit shifted hex',
	141	'Read/write bit shifted out from the 8-bit I2C slave address'],
	142	# ANN_SHIFTED_SHORT
	143	['7-bit shifted hex (short)',
	144	'Read/write bit shifted out from the 8-bit I2C slave address'],
	145	# ANN_RAW
	146	['Raw hex', 'Unaltered raw data'],
	147	]
	148
	149	def __init__(self, **kwargs):
	150	self.samplecnt = 0
	151	self.bitcount = 0
	152	self.databyte = 0
	153	self.wr = -1
	154	self.startsample = -1
	155	self.is_repeat_start = 0
	156	self.state = FIND_START
	157	self.oldscl = None
	158	self.oldsda = None
	159
	160	# Set protocol decoder option defaults.
	161	self.addressing = Decoder.options['addressing'][1]
	162
	163	def start(self, metadata):
	164	self.out_proto = self.add(srd.OUTPUT_PROTO, 'i2c')
	165	self.out_ann = self.add(srd.OUTPUT_ANN, 'i2c')
	166
	167	def report(self):
	168	pass
	169
	170	def is_start_condition(self, scl, sda):
	171	# START condition (S): SDA = falling, SCL = high
	172	if (self.oldsda == 1 and sda == 0) and scl == 1:
	173	return True
	174	return False
	175
	176	def is_data_bit(self, scl, sda):
	177	# Data sampling of receiver: SCL = rising
	178	if self.oldscl == 0 and scl == 1:
	179	return True
	180	return False
	181
	182	def is_stop_condition(self, scl, sda):
	183	# STOP condition (P): SDA = rising, SCL = high
	184	if (self.oldsda == 0 and sda == 1) and scl == 1:
	185	return True
	186	return False
	187
	188	def found_start(self, scl, sda):
	189	cmd = 'START_REPEAT' if (self.is_repeat_start == 1) else 'START'
	190
	191	self.put(self.out_proto, [cmd, None, None])
	192	self.put(self.out_ann, [ANN_SHIFTED, [protocol[cmd][0]]])
	193	self.put(self.out_ann, [ANN_SHIFTED_SHORT, [protocol[cmd][1]]])
	194
	195	self.state = FIND_ADDRESS
	196	self.bitcount = self.databyte = 0
	197	self.is_repeat_start = 1
	198	self.wr = -1
	199
	200	def found_address_or_data(self, scl, sda):
	201	# Gather 8 bits of data plus the ACK/NACK bit.
	202
	203	if self.startsample == -1:
	204	# TODO: Should be samplenum, as received from the feed.
	205	self.startsample = self.samplecnt
	206	self.bitcount += 1
	207
	208	# Address and data are transmitted MSB-first.
	209	self.databyte <<= 1
	210	self.databyte \|= sda
	211
	212	# Return if we haven't collected all 8 + 1 bits, yet.
	213	if self.bitcount != 9:
	214	return
	215
	216	# Send raw output annotation before we start shifting out
	217	# read/write and ack/nack bits.
	218	self.put(self.out_ann, [ANN_RAW, ['0x%.2x' % self.databyte]])
	219
	220	# We received 8 address/data bits and the ACK/NACK bit.
	221	self.databyte >>= 1 # Shift out unwanted ACK/NACK bit here.
	222
	223	if self.state == FIND_ADDRESS:
	224	# The READ/WRITE bit is only in address bytes, not data bytes.
	225	self.wr = 0 if (self.databyte & 1) else 1
	226	d = self.databyte >> 1
	227	elif self.state == FIND_DATA:
	228	d = self.databyte
	229	else:
	230	# TODO: Error?
	231	pass
	232
	233	# Last bit that came in was the ACK/NACK bit (1 = NACK).
	234	ack_bit = 'NACK' if (sda == 1) else 'ACK'
	235
	236	if self.state == FIND_ADDRESS and self.wr == 1:
	237	cmd = 'ADDRESS_WRITE'
	238	elif self.state == FIND_ADDRESS and self.wr == 0:
	239	cmd = 'ADDRESS_READ'
	240	elif self.state == FIND_DATA and self.wr == 1:
	241	cmd = 'DATA_WRITE'
	242	elif self.state == FIND_DATA and self.wr == 0:
	243	cmd = 'DATA_READ'
	244
	245	self.put(self.out_proto, [cmd, d, ack_bit])
	246	self.put(self.out_ann, [ANN_SHIFTED,
	247	[protocol[cmd][0], '0x%02x' % d, protocol[ack_bit][0]]])
	248	self.put(self.out_ann, [ANN_SHIFTED_SHORT,
	249	[protocol[cmd][1], '0x%02x' % d, protocol[ack_bit][1]]])
	250
	251	self.bitcount = self.databyte = 0
	252	self.startsample = -1
	253
	254	if self.state == FIND_ADDRESS:
	255	self.state = FIND_DATA
	256	elif self.state == FIND_DATA:
	257	# There could be multiple data bytes in a row.
	258	# So, either find a STOP condition or another data byte next.
	259	pass
	260
	261	def found_stop(self, scl, sda):
	262	self.put(self.out_proto, ['STOP', None, None])
	263	self.put(self.out_ann, [ANN_SHIFTED, [protocol['STOP'][0]]])
	264	self.put(self.out_ann, [ANN_SHIFTED_SHORT, [protocol['STOP'][1]]])
	265
	266	self.state = FIND_START
	267	self.is_repeat_start = 0
	268	self.wr = -1
	269
	270	def put(self, output_id, data):
	271	# Inject sample range into the call up to sigrok.
	272	# TODO: 0-0 sample range for now.
	273	super(Decoder, self).put(0, 0, output_id, data)
	274
	275	def decode(self, ss, es, data):
	276	for samplenum, (scl, sda) in data:
	277	self.samplecnt += 1
	278
	279	# First sample: Save SCL/SDA value.
	280	if self.oldscl == None:
	281	self.oldscl = scl
	282	self.oldsda = sda
	283	continue
	284
	285	# TODO: Wait until the bus is idle (SDA = SCL = 1) first?
	286
	287	# State machine.
	288	if self.state == FIND_START:
	289	if self.is_start_condition(scl, sda):
	290	self.found_start(scl, sda)
	291	elif self.state == FIND_ADDRESS:
	292	if self.is_data_bit(scl, sda):
	293	self.found_address_or_data(scl, sda)
	294	elif self.state == FIND_DATA:
	295	if self.is_data_bit(scl, sda):
	296	self.found_address_or_data(scl, sda)
	297	elif self.is_start_condition(scl, sda):
	298	self.found_start(scl, sda)
	299	elif self.is_stop_condition(scl, sda):
	300	self.found_stop(scl, sda)
	301	else:
	302	# TODO: Error?
	303	pass
	304
	305	# Save current SDA/SCL values for the next round.
	306	self.oldscl = scl
	307	self.oldsda = sda
	308