Poster Abstract: 12C Considered Wasteful Saving Energy with Host-Controlled Pull-Up Resistors

The Inter-Integrated Circuit (I
²
C) bus is frequently used to connect sensors and actuators to cyber-physical systems. It is designed around always-on pull-up resistors, which transform valuable electric energy into heat whenever a 0-signal is sent or received. Using a software I
²
C implementation which disables pull-ups when possible, we decrease the energy demand of I
²
C transmissions at the cost of additional CPU time. On a low-power MSP430FR5969 microcontroller, we observe 10 to 50 % lower whole-system energy usage per transmission compared to conventional software I
²
C. An advantage over hardware I
²
C modules is only apparent at bus clocks below 10 kHz.