ps2x2pico

USB keyboard/mouse to PS/2 interface converter using a Raspberry Pi Pico

Keyboard only (incl. PC-XT) variant: https://github.com/No0ne/ps2pico

PicoMiteVGA variant: https://github.com/No0ne/hid2cdc

PiKVM integration:

• https://docs.pikvm.org/pico_hid/
• https://docs.pikvm.org/pico_hid_bridge/

Usage

• Download ps2x2pico.uf2 from https://github.com/No0ne/ps2x2pico/releases
• Copy ps2x2pico.uf2 to your Pi Pico by pressing BOOTSEL before pluggging in.
• 3.3V/5V conversion is done using a bi-directional level shifter: https://learn.sparkfun.com/tutorials/bi-directional-logic-level-converter-hookup-guide/
• Afterwards connect a USB keyboard and/or mouse using an OTG-adapter and optional USB hub.
• Also works with wireless keyboards and mice with a dedicated USB receiver.

⚠️ Please note that some older motherboards have non-resettable fuses rated under 300mA.

Check the power consumption of your keyboard/mouse/hub first before plugging in!

⚠️ Do not assume wire colors will match cables depicted in photos. Double-check your pinout with a multimeter.

Troubleshooting

You can hook up a USB serial adapter to GPIO0 for additional debugging output. The serial settings are 115200 baud, 8 data bits and no parity. You can also use another Pico running the pico-uart-bridge for this.

⚠️ If you have a YD-RP2040 (see silkscreen on back of board if unsure) and are not using a USB hub with its own power supply, you need to bridge two pads of the diode pair near the USB-C port as seen here:

Build

(update to the latest TinyUSB release first)

export PICO_SDK_PATH=/path/to/pico-sdk
cd $PICO_SDK_PATH/lib/tinyusb
git checkout 0.16.0

cd /path/to/ps2x2pico
mkdir build
cd build
cmake ..
make

Resources

• https://github.com/No0ne/ps2pico
• https://wiki.osdev.org/PS/2_Keyboard
• https://wiki.osdev.org/PS/2_Mouse
• https://wiki.osdev.org/Mouse_Input
• https://wiki.osdev.org/%228042%22_PS/2_Controller
• http://www-ug.eecg.toronto.edu/msl/nios_devices/datasheets/PS2%20Keyboard%20Protocol.htm
• http://www-ug.eecg.utoronto.ca/desl/nios_devices_SoC/datasheets/PS2%20Mouse%20Protocol.htm
• Archive.org links for the dead links in the pages above
  • Main page PS/2 Keyboard Protocol
    • Scan code set 1
    • Scan code set 2
    • Scan code set 3
  • Main page PS/2 Mouse Protocol