diff options
Diffstat (limited to 'decoders/i2c')
| -rw-r--r-- | decoders/i2c/__init__.py | 58 | ||||
| -rw-r--r-- | decoders/i2c/i2c.py | 60 |
2 files changed, 58 insertions, 60 deletions
diff --git a/decoders/i2c/__init__.py b/decoders/i2c/__init__.py index 9e7856e..3c29aa1 100644 --- a/decoders/i2c/__init__.py +++ b/decoders/i2c/__init__.py @@ -18,5 +18,63 @@ ## 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 + +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. +''' + from .i2c import * diff --git a/decoders/i2c/i2c.py b/decoders/i2c/i2c.py index 527fa6e..b1c4a8a 100644 --- a/decoders/i2c/i2c.py +++ b/decoders/i2c/i2c.py @@ -18,46 +18,7 @@ ## 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. @@ -69,27 +30,6 @@ # 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 |