The MESA 7C81 is FPGA motherboard host for a Raspberry Pi CPU. The 7C81 connects to the RPI's GPIO interface and uses SPI for FPGA communication.
Three 26 pin header connectors with standard parallel port pinouts and 5V tolerant I/O are provided for compatibility with most parallel port interfaced motion control / CNC breakout cards/ multi axis step motor drives, including Mesa's 25 pin daughtercards. Mesa's 25 pin daughtercards or standard parallel port breakout boards allow almost unlimited I/O options including  quadrature or absolute encoder inputs, step/dir (to 10 MHz) or PWM/dir outputs, and field I/O expansion to hundreds of I/O points. In addition to the parallel expansion ports, the 7C81 provides two  RS-422/RS-485 interfaces for I/O expansion via serial I/O daughtercards.  The 7C81 mounts in standard 107 mm DIN rail channels and is powered by 5V