## 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 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 = 0
ANN_SHIFTED_SHORT = 1
-ANN_RAW = 2
+ANN_RAW = 2
# Values are verbose and short annotation, respectively.
protocol = {
{'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
}
]
def __init__(self, **kwargs):
- self.samplecnt = 0
+ self.startsample = -1
+ self.samplenum = None
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')
return False
def found_start(self, scl, sda):
- cmd = 'START REPEAT' if (self.is_repeat_start == 1) else 'START'
+ self.startsample = self.samplenum
+ 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.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):
- # 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
+ 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 != 9:
return
pass
def found_stop(self, scl, sda):
+ self.startsample = self.samplenum
+
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]]])
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)
+ super(Decoder, self).put(self.startsample, self.samplenum, output_id, data)
def decode(self, ss, es, data):
for samplenum, (scl, sda) in data:
- self.samplecnt += 1
+ self.samplenum = samplenum
# First sample: Save SCL/SDA value.
if self.oldscl == None:
elif self.is_stop_condition(scl, sda):
self.found_stop(scl, sda)
else:
- # TODO: Error?
- pass
+ raise Exception('Invalid state %d' % self.STATE)
# Save current SDA/SCL values for the next round.
self.oldscl = scl
projects / libsigrokdecode.git / blobdiff