The mikroPascal PRO for dsPIC30/33 and PIC24 provides a library for communication with the common PS/2 keyboard.

  Important :

• The library does not utilize interrupts for data retrieval, and requires the oscillator clock to be at least 6MHz.
• The pins to which a PS/2 keyboard is attached should be connected to the pull-up resistors.
• Although PS/2 is a two-way communication bus, this library does not provide MCU-to-keyboard communication; e.g. pressing the Caps Lock key will not turn on the Caps Lock LED.

External dependencies of PS/2 Library

Library Routines

• Ps2_Config
• Ps2_Key_Read

Ps2_Config

// PS2 pinout definition 
var PS2_Data : sbit at RB0_bit;
var PS2_Clock : sbit at RB1_bit;
var PS2_Data_Direction : sbit at TRISB0_bit; 
var PS2_Clock_Direction : sbit at TRISB1_bit;
// End of PS2 pinout definition// Init PS/2 Keyboard

Ps2_Key_Read

var value, special, pressed : word;
...
// Press Enter to continue:
repeat {
  if (Ps2_Key_Read(value, special, pressed)) then 
    if ((value = 13) and (special = 1)) then break;
until (0=1);

Special Function Keys

Library Example

This simple example reads values of the pressed keys on the PS/2 keyboard and sends them via UART.

Copy Code To Clipboard

program PS2_Example;

var keydata, special, down : byte;

var PS2_Data            : sbit at RB0_bit;
    PS2_Clock           : sbit at RB1_bit;
    PS2_Data_Direction  : sbit at TRISB0_bit;
    PS2_Clock_Direction : sbit at TRISB1_bit;

begin

  ADPCFG := 0xFFFF;            // Configure AN pins as digital I/O

  UART1_Init(19200);           // Initialize UART module at 19200 bps


  Ps2_Config();                // Init PS/2 Keyboard
  Delay_ms(100);               // Wait for keyboard to finish
  UART1_Write_Text('Ready');   // Ready
  UART1_Write(13);             // Line Feed
  UART1_Write(10);             // Carriage return


    while TRUE do                                                         // Endless loop
      begin
        if Ps2_Key_Read(keydata, special, down) then                      // If data was read from PS/2
          begin
            if (down <> 0) and (keydata = 16) then                        // Backspace
              begin
                UART1_Write(0x08);                                        // Send Backspace to usart terminal
              end
            else if (down <> 0) and (keydata = 13) then                   // Enter
              begin
                UART1_Write(10);                                          // Send carriage return to usart terminal
                UART1_Write(13);                                          // Uncomment this line if usart terminal also expects line feed
                                                                          // for new line transition
              end
            else if (down <> 0) and (special = 0) and (keydata <> 0) then // Common key read
              begin
                UART1_Write(keydata);                                     // Send key to usart terminal
              end;
          end;
        Delay_ms(1);                                                      // Debounce period
      end;
end.

HW Connection

Example of PS2 keyboard connection

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