41. PS/2 Keyboard Test

Now a computer is no good, unless you can type something into it.  Although it is possible to read a USB keyboard you need additional hardware if you are just using an Arduino UNO.  However there is an Arduino library for PS/2 Keyboards. I found it at http://www.pjrc.com/teensy/td_libs_PS2Keyboard.html.  You'll need to add it to the Arduino IDE Libraries. Click on Sketch->Import Library->Add Library...

All I needed now was a PS/2 Keyboard as all my keyboards are USB these days.  Fortunately they can still be found in plentiful supply at your favourite online stores.

Of course, with s PS/2 keyboard you need a PS/2 socket to plug it in.  I had an old motherboard and a hot air gun soon melted the solder to free it from the main board.  Now to make it breadboard friendly.

You only need 4 pins.  +5V, GND, Clock and Data.  See http://en.wikipedia.org/wiki/PS/2_port for details of the pin outs.  I used a continuity tester to check which pins underneath matched which ps/2 port inputs and soldered on four jump wires.

Using just the LiquidCrystal library and the PS2Keyboard library, I was able to write all over my 20x4 LCD display.

The PS2Keyboard library defaults to US layout doesnt have the UK layout defined so I might tweak that later.

Heres the code:
#include <LiquidCrystal.h>

#include <PS2Keyboard.h>

LiquidCrystal lcd(10,9,8,7,6,5,4);
PS2Keyboard keyboard;
const int DataPin = 3;
const int IRQpin =  2;

int row=1;
int col=0;

void setup() {
  // put your setup code here, to run once:
  delay(1000);
  keyboard.begin(DataPin, IRQpin);
  lcd.begin(20,4);
  lcd.print("Keyboard Test");
  //lcd.cursor();
  lcd.blink();
  lcd.setCursor(col,row);

}

void loop() {
  // put your main code here, to run repeatedly: 
  if (keyboard.available()) {
    
    // read the next key
    char c = keyboard.read();
    
    // check for some of the special keys
    if (c == PS2_ENTER) {
      col=0;
      row=row+1;
    } else if (c == PS2_ESC) {
      lcd.clear();  // clear screen if ESC is pressed.
      col=0;
      row=0;
    } else if (c == PS2_LEFTARROW) {
      col=col-1;
    } else if (c == PS2_RIGHTARROW) {
      col=col+1;
    } else if (c == PS2_UPARROW) {
      row=row-1;
    } else if (c == PS2_DOWNARROW) {
      row=row+1;
    } else if (c == PS2_DELETE) {
      col=col-1;
      lcd.setCursor(col,row);
      c=32;
      lcd.print(c);
      lcd.setCursor(col,row);
    } else {
      
      // otherwise, just print all normal characters
      lcd.print(c);
      col=col+1;
   }
   if (col>19) {
     col=0;
     row=row+1;
   }
   if (col<0) {
     col=19;
     row=row-1;
   }
   if (row>3) row=0;
   if (row<0) row=3;
  }
  lcd.setCursor(col,row);
}