## 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
{'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
}
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:
elif self.is_stop_condition(scl, sda):
self.found_stop(scl, sda)
else:
- # Shouldn't happen.
- raise Exception("unknown state %d" % self.STATE)
+ raise Exception('Invalid state %d' % self.STATE)
# Save current SDA/SCL values for the next round.
self.oldscl = scl