I2C Bus

The I2C bus interface allows you to decode traffic sent over the I2C SDA line. In order to decode the traffic a number of parameters need to be set based on your knowledge how the I2C bus should be operating.

Creating an I2C Bus

To create an I2C bus a scl (clock) net and sda (data) net need to be instantiated.

create_i2c_bus.py

 from lager import Net, NetType, I2C

 sda = Net.get('I2C.SDA',
         type=NetType.Logic,
         setup_function=setup_nets,
         teardown_function=teardown_nets)

 scl = Net.get('I2C.SCL',
         type=NetType.Logic,
         setup_function=setup_nets,
         teardown_function=teardown_nets)

 i2c = I2C(scl=scl,sda=sda)
 i2c.enable()

Create I2C Bus

~  lager bus i2c --source-scl I2C.SCL --source-sda I2C.SDA --dut 1

Including RW Bit

When decoding I2C communication it may be useful to either include the r/w bit in the address byte.

include_rw_bit.py

 from lager import Net, NetType, I2C

 sda = Net.get('I2C.SDA',
         type=NetType.Logic,
         setup_function=setup_nets,
         teardown_function=teardown_nets)

 scl = Net.get('I2C.SCL',
         type=NetType.Logic,
         setup_function=setup_nets,
         teardown_function=teardown_nets)

 i2c = I2C(scl=scl,sda=sda)
 i2c.rw_on()

Include R/W Bit

~  lager bus i2c --rw on --dut 1

Signal Threshold

This sets the assumed voltage threshold a rising or falling I2C signal should pass through.

set_i2c_threshold.py

 from lager import Net, NetType, I2C

 scl = Net.get('I2C.SCL',
         type=NetType.Logic,
         setup_function=setup_nets,
         teardown_function=teardown_nets)

 sda = Net.get('I2C.SDA',
         type=NetType.Logic,
         setup_function=setup_nets,
         teardown_function=teardown_nets)

 i2c = I2C(scl=scl,sda=sda)
 i2c.set_signal_threshold(scl=1.5, sda=1.5)

Set I2C Bus Threshold

~  lager bus i2c --level-scl 1.5 --level-sda 1.5 --dut 1