##
## This file is part of the libsigrokdecode project.
##
## Copyright (C) 2010-2016 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, see <http://www.gnu.org/licenses/>.
##
# TODO: Look into arbitration, collision detection, clock synchronisation, etc.
# TODO: Implement support for inverting SDA/SCL levels (0->1 and 1->0).
# TODO: Implement support for detecting various bus errors.
from common.srdhelper import bitpack_msb
import sigrokdecode as srd
'''
OUTPUT_PYTHON format:
Packet:
[<ptype>, <pdata>]
<ptype>:
- 'START' (START condition)
- 'START REPEAT' (Repeated START condition)
- 'ADDRESS READ' (Slave address, read)
- 'ADDRESS WRITE' (Slave address, write)
- 'DATA READ' (Data, read)
- 'DATA WRITE' (Data, write)
- 'STOP' (STOP condition)
- 'ACK' (ACK bit)
- 'NACK' (NACK bit)
- 'BITS' (<pdata>: list of data/address bits and their ss/es numbers)
<pdata> is the data or address byte associated with the 'ADDRESS*' and 'DATA*'
command. Slave addresses do not include bit 0 (the READ/WRITE indication bit).
For example, a slave address field could be 0x51 (instead of 0xa2).
For 'START', 'START REPEAT', 'STOP', 'ACK', and 'NACK' <pdata> is None.
For 'BITS' <pdata> is a sequence of tuples of bit values and their start and
stop positions, in LSB first order (although the I2C protocol is MSB first).
'''
# Meaning of table items:
# command -> [annotation class, annotation text in order of decreasing length]
proto = {
'START': [0, 'Start', 'S'],
'START REPEAT': [1, 'Start repeat', 'Sr'],
'STOP': [2, 'Stop', 'P'],
'ACK': [3, 'ACK', 'A'],
'NACK': [4, 'NACK', 'N'],
'BIT': [5, '{b:1d}'],
'ADDRESS READ': [6, 'Address read: {b:02X}', 'AR: {b:02X}', '{b:02X}'],
'ADDRESS WRITE': [7, 'Address write: {b:02X}', 'AW: {b:02X}', '{b:02X}'],
'DATA READ': [8, 'Data read: {b:02X}', 'DR: {b:02X}', '{b:02X}'],
'DATA WRITE': [9, 'Data write: {b:02X}', 'DW: {b:02X}', '{b:02X}'],
'WARN': [10, '{text}'],
}
class Decoder(srd.Decoder):
api_version = 3
id = 'i2c'
name = 'I²C'
longname = 'Inter-Integrated Circuit'
desc = 'Two-wire, multi-master, serial bus.'
license = 'gplv2+'
inputs = ['logic']
outputs = ['i2c']
tags = ['Embedded/industrial']
channels = (
{'id': 'scl', 'name': 'SCL', 'desc': 'Serial clock line'},
{'id': 'sda', 'name': 'SDA', 'desc': 'Serial data line'},
)
options = (
{'id': 'address_format', 'desc': 'Displayed slave address format',
'default': 'shifted', 'values': ('shifted', 'unshifted')},
)
annotations = (
('start', 'Start condition'),
('repeat-start', 'Repeat start condition'),
('stop', 'Stop condition'),
('ack', 'ACK'),
('nack', 'NACK'),
('bit', 'Data/address bit'),
('address-read', 'Address read'),
('address-write', 'Address write'),
('data-read', 'Data read'),
('data-write', 'Data write'),
('warning', 'Warning'),
)
annotation_rows = (
('bits', 'Bits', (5,)),
('addr-data', 'Address/data', (0, 1, 2, 3, 4, 6, 7, 8, 9)),
('warnings', 'Warnings', (10,)),
)
binary = (
('address-read', 'Address read'),
('address-write', 'Address write'),
('data-read', 'Data read'),
('data-write', 'Data write'),
)
def __init__(self):
self.reset()
def reset(self):
self.samplerate = None
self.is_write = None
self.rem_addr_bytes = None
self.slave_addr_7 = None
self.slave_addr_10 = None
self.is_repeat_start = False
self.pdu_start = None
self.pdu_bits = 0
self.data_bits = []
self.bitwidth = 0
def metadata(self, key, value):
if key == srd.SRD_CONF_SAMPLERATE:
self.samplerate = value
def start(self):
self.out_python = self.register(srd.OUTPUT_PYTHON)
self.out_ann = self.register(srd.OUTPUT_ANN)
self.out_binary = self.register(srd.OUTPUT_BINARY)
self.out_bitrate = self.register(srd.OUTPUT_META,
meta=(int, 'Bitrate', 'Bitrate from Start bit to Stop bit'))
def putg(self, ss, es, cls, text):
self.put(ss, es, self.out_ann, [cls, text])
def putp(self, ss, es, data):
self.put(ss, es, self.out_python, data)
def putb(self, ss, es, data):
self.put(ss, es, self.out_binary, data)
def _wants_start(self):
# Check whether START is required (to sync to the input stream).
return self.pdu_start is None
def _collects_address(self):
# Check whether the transfer still is in the address phase (is
# still collecting address and r/w details, or has not started
# collecting it).
return self.rem_addr_bytes is None or self.rem_addr_bytes != 0
def _collects_byte(self):
# Check whether bits of a byte are being collected. Outside of
# the data byte, the bit is the ACK/NAK slot.
return self.data_bits is None or len(self.data_bits) < 8
def handle_start(self, ss, es):
if self.is_repeat_start:
cmd = 'START REPEAT'
else:
cmd = 'START'
self.pdu_start = ss
self.pdu_bits = 0
self.putp(ss, es, [cmd, None])
cls, texts = proto[cmd][0], proto[cmd][1:]
self.putg(ss, es, cls, texts)
self.is_repeat_start = True
self.is_write = None
self.slave_addr_7 = None
self.slave_addr_10 = None
self.rem_addr_bytes = None
self.data_bits.clear()
self.bitwidth = 0
# Gather 8 bits of data plus the ACK/NACK bit.
def handle_address_or_data(self, ss, es, value):
self.pdu_bits += 1
# Accumulate a byte's bits, including its start position.
# Accumulate individual bits and their start/end sample numbers
# as we see them. Get the start sample number at the time when
# the bit value gets sampled. Assume the start of the next bit
# as the end sample number of the previous bit. Guess the last
# bit's end sample number from the second last bit's width.
# Keep the bits in receive order (MSB first) during accumulation.
# (gsi: Strictly speaking falling SCL would be the end of the
# bit value's validity. That'd break compatibility though.)
if self.data_bits:
self.data_bits[-1][2] = ss
self.data_bits.append([value, ss, es])
if len(self.data_bits) < 8:
return
self.bitwidth = self.data_bits[-2][2] - self.data_bits[-3][2]
self.data_bits[-1][2] = self.data_bits[-1][1] + self.bitwidth
# Get the byte value. Address and data are transmitted MSB-first.
d = bitpack_msb(self.data_bits, 0)
ss_byte, es_byte = self.data_bits[0][1], self.data_bits[-1][2]
# Process the address bytes at the start of a transfer. The
# first byte will carry the R/W bit, and all of the 7bit address
# or part of a 10bit address. Bit pattern 0b11110xxx signals
# that another byte follows which carries the remaining bits of
# a 10bit slave address.
is_address = self._collects_address()
if is_address:
addr_byte = d
if self.rem_addr_bytes is None:
if (addr_byte & 0xf8) == 0xf0:
self.rem_addr_bytes = 2
self.slave_addr_7 = None
self.slave_addr_10 = addr_byte & 0x06
self.slave_addr_10 <<= 7
else:
self.rem_addr_bytes = 1
self.slave_addr_7 = addr_byte >> 1
self.slave_addr_10 = None
has_rw_bit = self.is_write is None
if self.is_write is None:
read_bit = bool(addr_byte & 1)
if self.options['address_format'] == 'shifted':
d >>= 1
self.is_write = False if read_bit else True
elif self.slave_addr_10 is not None:
self.slave_addr_10 |= addr_byte
else:
cls, texts = proto['WARN'][0], proto['WARN'][1:]
msg = 'Unhandled address byte'
texts = [t.format(text = msg) for t in texts]
self.putg(ss_byte, es_byte, cls, texts)
is_write = self.is_write
is_seven = self.slave_addr_7 is not None
# Determine annotation classes depending on whether the byte is
# an address or payload data, and whether it's written or read.
bin_class = -1
if is_address and is_write:
cmd = 'ADDRESS WRITE'
bin_class = 1
elif is_address and not is_write:
cmd = 'ADDRESS READ'
bin_class = 0
elif not is_address and is_write:
cmd = 'DATA WRITE'
bin_class = 3
elif not is_address and not is_write:
cmd = 'DATA READ'
bin_class = 2
# Reverse the list of bits to LSB first order before emitting
# annotations and passing bits to upper layers. This may be
# unexpected because the protocol is MSB first, but it keeps
# backwards compatibility.
lsb_bits = self.data_bits[:]
lsb_bits.reverse()
self.putp(ss_byte, es_byte, ['BITS', lsb_bits])
self.putp(ss_byte, es_byte, [cmd, d])
self.putb(ss_byte, es_byte, [bin_class, bytes([d])])
for bit_value, ss_bit, es_bit in lsb_bits:
cls, texts = proto['BIT'][0], proto['BIT'][1:]
texts = [t.format(b = bit_value) for t in texts]
self.putg(ss_bit, es_bit, cls, texts)
if is_address and has_rw_bit:
# Assign the last bit's location to the R/W annotation.
# Adjust the address value's location to the left.
ss_bit, es_bit = self.data_bits[-1][1], self.data_bits[-1][2]
es_byte = self.data_bits[-2][2]
cls = proto[cmd][0]
w = ['Write', 'Wr', 'W'] if self.is_write else ['Read', 'Rd', 'R']
self.putg(ss_bit, es_bit, cls, w)
cls, texts = proto[cmd][0], proto[cmd][1:]
texts = [t.format(b = d) for t in texts]
self.putg(ss_byte, es_byte, cls, texts)
def get_ack(self, ss, es, value):
ss_bit, es_bit = ss, es
cmd = 'ACK' if value == 0 else 'NACK'
self.putp(ss_bit, es_bit, [cmd, None])
cls, texts = proto[cmd][0], proto[cmd][1:]
self.putg(ss_bit, es_bit, cls, texts)
# Slave addresses can span one or two bytes, before data bytes
# follow. There can be an arbitrary number of data bytes. Stick
# with getting more address bytes if applicable, or enter or
# remain in the data phase of the transfer otherwise.
if self.rem_addr_bytes:
self.rem_addr_bytes -= 1
self.data_bits.clear()
def handle_stop(self, ss, es):
# Meta bitrate
if self.samplerate and self.pdu_start:
elapsed = es - self.pdu_start + 1
elapsed /= self.samplerate
bitrate = int(1 / elapsed * self.pdu_bits)
ss_meta, es_meta = self.pdu_start, es
self.put(ss_meta, es_meta, self.out_bitrate, bitrate)
self.pdu_start = None
self.pdu_bits = 0
cmd = 'STOP'
self.putp(ss, es, [cmd, None])
cls, texts = proto[cmd][0], proto[cmd][1:]
self.putg(ss, es, cls, texts)
self.is_repeat_start = False
self.is_write = None
self.data_bits.clear()
def decode(self):
# Check for several bus conditions. Determine sample numbers
# here and pass ss, es, and bit values to handling routines.
while True:
# State machine.
# BEWARE! This implementation expects to see valid traffic,
# is rather picky in which phase which symbols get handled.
# This attempts to support severely undersampled captures,
# which a previous implementation happened to read instead
# of rejecting the inadequate input data.
# NOTE that handling bits at the start of their validity,
# and assuming that they remain valid until the next bit
# starts, is also done for backwards compatibility.
if self._wants_start():
# Wait for a START condition (S): SCL = high, SDA = falling.
pins = self.wait({0: 'h', 1: 'f'})
ss, es = self.samplenum, self.samplenum
self.handle_start(ss, es)
elif self._collects_address() and self._collects_byte():
# Wait for a data bit: SCL = rising.
pins = self.wait({0: 'r'})
_, sda = pins
ss, es = self.samplenum, self.samplenum + self.bitwidth
self.handle_address_or_data(ss, es, sda)
elif self._collects_byte():
# Wait for any of the following conditions (or combinations):
# a) Data sampling of receiver: SCL = rising, and/or
# b) START condition (S): SCL = high, SDA = falling, and/or
# c) STOP condition (P): SCL = high, SDA = rising
pins = self.wait([{0: 'r'}, {0: 'h', 1: 'f'}, {0: 'h', 1: 'r'}])
# Check which of the condition(s) matched and handle them.
if self.matched[0]:
_, sda = pins
ss, es = self.samplenum, self.samplenum + self.bitwidth
self.handle_address_or_data(ss, es, sda)
elif self.matched[1]:
ss, es = self.samplenum, self.samplenum
self.handle_start(ss, es)
elif self.matched[2]:
ss, es = self.samplenum, self.samplenum
self.handle_stop(ss, es)
else:
# Wait for a data/ack bit: SCL = rising.
pins = self.wait({0: 'r'})
_, sda = pins
ss, es = self.samplenum, self.samplenum + self.bitwidth
self.get_ack(ss, es, sda)