PS2 Keyboard

This is the keyboard interface for the PC-XT with a PS2 keyboard. It is based on an AVR ATmega328p that implements a PS2 keyboard interface and a PC-XT interface.

The AVR connects directly into the PC-XT 8255 PPI Port A, bypassing the serial XT keyboard interface. The AVR code configures the keyboard, accepts scan codes, converts the AT scan codes to XT keyboard codes, and transfers them to the PC-XT.

The AVR to PC-XT interface is a parallel interface that uses two handshake signals: a data ready signal into the PC's IRQ1 keyboard interrupt line, and a busy/ready signal from the PC to the AVR.

AVR C code can be found here https://github.com/eyalabraham/ps2kbd.

Schematics in PDF format: PS2 to PCXT board.

The motherboard keyboard hack to pass IRQ1 from AVR to the systems.