operating-a-4-x-4-keyboard

Example 5 – Operating a 4 x 4 keyboard

The example shows the connection of a 4 x 4 keyboard to a dsPIC30F6014A microcontroller. The example shows decoding the keyboard [0...15] to obtain ASCII symbols [0...9,A...F]. Also shown is a counter of the pressed keys. The value of the counter is written in the second line of an LCD module. The realization is carried out by using the mikroPascal compiler for dsPIC30F microcontrollers. Fig. 13-5 shows the interconnection of the keyboard and a dsPIC30F6014A microcontroller.

pic-microcontrollers-programming-dspic-in-pascal-chapter-13-image-5

Fig. 13-5 Interconnection of the keyboard and a dsPIC30F6014A microcontroller

program Keypad_4x4_test;

var kp, oldkp  : byte;
    cnt : word;
    txt : string[6];

begin
  cnt := 0;
  Keypad_Init(PORTF);

  ADPCFG := $FFFF;
  Glcd_Init_DsPicPro3();
  Glcd_Fill(0x00);
  Glcd_Set_Font(@FontSystem5x8, 5, 8, 32);
  Glcd_Write_Text('Keypad 4x4 example', 10, 0, 1);
  Glcd_Write_Text('Key pressed :', 10, 3, 1);
  Glcd_Write_Text('Times :'      , 10, 6, 1);

  oldkp := 1;

  while TRUE do
  begin
    nop;
    kp := 0;
    // Wait for key to be pressed
    while kp = 0 do
      kp := Keypad_Key_Click();

    if oldkp = kp then
      Inc(cnt)
    else
      cnt := 1;

    oldkp := kp;

    // Prepare value for output
    case kp of
       1: kp := 49;  // 1
       2: kp := 50;  // 2
       3: kp := 51;  // 3
       4: kp := 65;  // A
       5: kp := 52;  // 4
       6: kp := 53;  // 5
       7: kp := 54;  // 6
       8: kp := 66;  // B
       9: kp := 55;  // 7
      10: kp := 56;  // 8
      11: kp := 57;  // 9
      12: kp := 67;  // C
      13: kp := 42;  // *
      14: kp := 48;  // 0
      15: kp := 35;  // #
      16: kp := 68;  // D
    end;

    Glcd_Write_Char(kp, 30, 4, 1);

    if cnt = 65535 then
      cnt := 0;

    // Print on LCD
    WordToStr(cnt, txt);
    Glcd_Write_Text(txt, 10, 7, 1);

  end; //while

end.

Also, an example is given of the clearance by the software of the errors caused by the keyborad bounsing using the same connection as shown in Fig. 13-5. The realization is carried out by using the mikroPascal compiler for dsPIC30F microcontrollers.

program Button_test;

begin
  ADPCFG := $FFFF;
  TRISF := $0000;

  LATF := $AAAA;
  Delay_ms(200);
  LATF := $0000;

  while TRUE do
  begin               // if button on PORTB.0 is logic high for 100ms
    if Button(PORTB, 0, 100, 1) = 1 then
      LATF := $0001
    else
      if Button(PORTB, 1, 100, 1) = 1 then
        LATF := $0002
      else
        if Button(PORTB, 2, 100, 1) = 1 then
          LATF := $0004
        else
          if Button(PORTB, 3, 100, 1) = 1 then
            LATF := $0008
          else LATF := 0;
  end;

end.