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 mikroBasic compiler for dsPIC30F microcontrollers. Fig. 13-5 shows the interconnection of the keyboard and a dsPIC30F6014A microcontroller.

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

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

program Keypad_4x4_test

dim kp, oldkp  as byte
    cnt as word
    txt as string[6]

main:
  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
    nop
    kp = 0
    ' Wait for key to be pressed
    while kp = 0
      kp = Keypad_Key_Click()
    wend

    if oldkp = kp then
      Inc(cnt)
    else
      cnt = 1
    end if
    
    oldkp = kp

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

    Glcd_Write_Char(kp, 30, 4, 1)

    if cnt = 65535 then
      cnt = 0
    end if

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

  wend '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 mikroBasic compiler for dsPIC30F microcontrollers.

program Button_Test

main:
  ADPCFG = $FFFF
  TRISF = $0000

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

  while true
    ' if button on portb.0 is 5v 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 if
        end if
      end if
    end if
  wend
end.