PS/2 Keyboard Support Library for Raspberry Pico

Keyboard signals are decoded using a PIO state machine then converted to ASCII code by the library.

Wiring

There are 4 wires in the PS/2 keyboard interface.

V+    Connect to Pico 3.3V pin
GND   Connect to Pico ground pin
DATA  Connect to GPIO14 pin
CLOCK Connect to GPIO15 pin

NOTE: PS/2 keyboards were designed to operate at 5V. These connections assume that yours will operate correctly at 3.3V volts. Not all do. Under no circumstance try powering at 5V without also implementing level shifting for the clock and data, otherwise you could damage the GPIO ports.

Building the project from source

Pre-requisite: git c pico-sdk

git clone https://github.com/lurk101/pico-ps2kbd.git
cd pico-ps2kbd
git submodule update --init
mkdir b
cd b
cmake ..
make

API

// Initialize PS/2 keyboard support
// Parameters
//     pio  - keyboard suport pio number. 0 or 1
//     gpio - GPIO number of data pin, ctl pin must be on next
//            adjacent GPIO
// Returns  - none
void kbd_init(uint pio, uint gpio);

// Return keyboard status
// Parameters - none
// Returns  - 0 for not ready, otherwise ready
int kbd_ready(void);

// Blocking keyboard read
// Parameters - none
// Returns  - single ASCII character
char kbd_getc(void);

Example output

PS/2 KDB example
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