The I2C spec gives you a minimum and maximum rise time, but does not specify resistor values. Those values should be selected based on the total capacitance of

The I2C spec gives you a minimum and maximum rise time, but does not specify resistor values. Those values should be selected based on the total capacitance of the bus to meet the rise time requirement, either calculated or measured. The I2C specification is full of these kinds of ambiguities, which creates a lot more work for implementers. SMBus's physical layer is a subset of I2C that tightens these requirements and specifies pull-up current, making these calculations quite a bit easier. http://www.smbus.org/specs/SMBus_3_2_20220112.pdf http://www.smbus.org/specs/SMBus_3_2_20220112.pdf