General

The PS2Keyboard library uses one of the two available external interrupts to react on keyboard input. Once such input is received, it's stored in a one-byte buffer and is available to be read.

Latest Version

Version 2.2 - Adds non-US keyboard support, recovery from false input, buffering, shift key handling and much more.

Connection

The following schematic shows how to connect a PS/2 connector:

Make sure you connect the Clock PIN to the digital PIN 3 on the Arduino. Otherwise the interrupt, and therefore the whole library, won't work.

Usage

Below is a simple example on how to use the library. For more keycode constants have a look at the PS2Keyboard.h file.

#include <PS2Keyboard.h>

#define DATA_PIN 4
PS2Keyboard keyboard;

void setup() {
  keyboard.begin(DATA_PIN);

  Serial.begin(9600);
  Serial.println("hi");
  delay(1000);
}

void loop() {
  if(keyboard.available()) {
    byte dat = keyboard.read();
    byte val = dat - '0';

    if(val >= 0 && val <= 9) {
      Serial.print(val, DEC);
    } else if(dat == PS2_KC_ENTER) {
      Serial.println();
    } else if(dat == PS2_KC_ESC) {
      Serial.println("[ESC]");
    } 
  }
}

Download

This library is at a very early stage. If anyone wants to revise/rewrite it, feel free to do so (published under the LGPL). Attach:PS2Keyboard002.zip

FULL KEYBOARD IMPLEMENTATION CONTAINED IN PS2Keyboard_014A

Attach:PS2Keyboard_014A.zip

NOTE: PS2Keyboard_014A is the library to use beginning with Arduino 0013. ** It contains a full complement of letters, numbers and punctuation (excluding shifted characters/symbols). **

EDITED VERSION FOR EASY ASSIGNEMENT OF THE IRQ PIN

Download with example code from this link: http://www.megaupload.com/?d=MN6A8JC0

This is the standar library but with a little change in the begin() method for supporting a easy way for editing the irq pin and you never need to edit the .cpp file for changing it.

You only must do ....begin(datapin,interrupt_pin);

In case you enter a non valid value the digital pin 2 is automatically assigned.

Questions cuninganreset@gmail.com

Thanks to Andreas Christoffersen, i didn't see the bug before.

EDITED AGAIN - Actually mostly rewritten - Version 2.0

http://www.pjrc.com/teensy/td_libs_PS2Keyboard.html

Version 2.0 adds the following improvements:

• Scan Code Buffering: Data captured by the interrupt is stored into a circular buffer, so several keystrokes can be buffered if your sketch is busy and can not call read() between each one. Buffering also retains key break (up) events. Previous versions buffered only a single scan code and discarded all key break codes.
• Shift Key State: The state of both shift keys is tracked, so conversion to ASCII produces proper upper and lower case characters. The numbers and other dual character keys also properly respond to shift. Previous versions were limited to only uppercase and non-shift output.
• ASCII Only Output: The read() function returns only ASCII characters, or special keys mapped to ASCII control characters. Previous versions returned a mix of ASCII and raw scan codes, with no way to distinguish between them.
• Efficient Conversion: Fast table lookup has replaced a slow linear search algorithm.
• Multi-Board Support: Arduino Mega, Teensy and Sanguino interrupt pins are supported. Other boards can be easily added, or will work automatically if their core files define certain aliases.

Some of the information on this page is now obsolete. Please refer to the version 2.0 page for up-to-date documentation.

Version 2.1

http://www.pjrc.com/teensy/td_libs_PS2Keyboard.html

Version 2.1 adds the following improvements:

• Automatically resync bitstream after a 1/4 second timeout.
• Compatible with Arduino "new-extension" branch.

Further readings

• http://www.beyondlogic.org/keyboard/keybrd.htm
• http://www.computer-engineering.org/ps2keyboard/scancodes2.html
• BarcodeScanner
• PS2KeyboardExt

Suggestions

Rename charAvailable() to available() and readChar() to read() for consistency with other libraries.

Bug

Missing 'byte' declaration

Can be fixed by adding

#include "binary.h"
typedef uint8_t boolean;
typedef uint8_t byte;

scottp@dd.com.au

interesting additonal links: http://nocommercialpotential.posterous.com/interfacing-the-ps2-keyboard

Thanks to cassettica - http://arduino.cc/forum/index.php/topic,89943.0.html