Hey David,
The Onefinity CNC Controller of the Original/X-50/PRO Series is based on a software and hardware fork of an older version of the Buildbotics CNC controller software and hardware sources and is made and further developed by Onefinity. So either you ask them, or an electronics engineer friend with the appropriate knowledge. The source of the hardware is here: onefinity-pcb, the schematics of the AVR board is here: schematics, the layout of the AVR board is here: Gerber, the source of the software is here: onefinity-firmware. Both the Onefinity and the Buildbotics software and hardware are published under a free license (Free and open-source software and Open-source hardware).
Welcome to the forum!