The higher layers, namely the signaling and protocol issues, are already defined to be the same as Philips' Inter-Integrated Circuit (I²C) bus.
Some buses like I²C use multi-mastering inherently to allow any node to initiate a transfer with another node.
The display driver will typically accept commands and data using an industry-standard general-purpose serial or parallel interface, such as TTL, CMOS, RS232, SPI, voltage, current, timing and demultiplexing to make the display show the desired text or image.
The qfix controller boards consist of an Atmel AVR controller plus motor drivers, analog and digital input ports, LEDs, buttons, and an I²C bus.