One example includes a master microcontroller in a communication interface system. The microcontroller includes a transmitter configured to generate a clock signal at a selected frequency and to provide the clock signal to a slave microcontroller on a two-wire communication cable during a clock learning mode. The transmitter can be further configured to provide master data signal requests at the selected frequency on the two-wire communication cable during a data transfer mode. The microcontroller also includes a receiver configured to receive slave data signals at the variable frequency via the two-wire communication cable in response to the master data signal requests during the data transfer mode.