' Name        : KEYXT.pbp
' Compiler    : PICBASIC PRO Compiler 2.6
' Assembler   : PM or MPASM
' Target PIC  : PIC16F877-20, PIC18F452 or similar type
' Hardware    : LAB-XT Experimenter Board
' Oscillator  : 20MHz external
' Keywords    : DCD, HPWM, LCDOUT, LOOKUP, NCD
' Description : PICBASIC PRO program to display key label on LCD.
'

' MeLabs PIC programmer should not be connected to the ICSP header
' when running this code. It may interfere with the operation
' of the keypad.  

Define LOADER_USED 1  ' Only required for melabs Loader

Define OSC 20         ' Match the crystal on the board

' Define LCD registers and bits
Define LCD_DREG  PORTD
Define LCD_DBIT  4
Define LCD_RSREG PORTE
Define LCD_RSBIT 0
Define LCD_EREG  PORTE
Define LCD_EBIT  1

' Define program variables
col      Var Byte       ' Keypad column
row      Var Byte       ' Keypad row
key      Var Byte       ' Key value
disp_key Var Byte       ' Key ASCII value

   OPTION_REG.7 = 0     ' Enable PORTB pullups (16F877)
   'INTCON2.7 = 0       ' Enable PORTB pullups (18F452)
   ADCON1 = 7           ' Make PORTA and PORTE digital
   Pause 150            ' Wait for LCD to start

   LCDOut $fe, 1, "Press any key"  ' Display sign on message

mainloop:
   GoSub getkey          ' Get a key from the keypad
   IF key != $FF Then    ' Check to see if a key was pressed
      LCDOut $fe, 1, disp_key ' Display ASCII key label
   EndIF
   GoTo mainloop         ' Do it forever

' Subroutine to get a key from keypad
getkey:
   ' Check for keypress
   For row = 0 TO 3       ' Loop for 4 rows in keypad
     PORTB = 0            ' All output pins low
     TRISB = ~(DCD row)   ' Set one row pin to output
     '@ NOP               ' Fudge for 18F452
     col = PORTB >> 4     ' Read column pins
     IF col != $0F Then   ' Check if key is pressed
        HPwm 1,127,7500   ' Begin speaker tick
        GoTo gotkey       ' If any keydown, exit
     EndIF
   Next row               ' Repeat for the next row
        
   key = $FF              ' No keys down, set key to $FF
   Return                 ' Return to main loop
        
gotkey:                   ' Change row and column to key number 0 - 15
   Pause 15               ' Debounce
   HPwm 1,0,0             ' End speaker tick
        
   ' Wait for all keys up
   PORTB = 0               ' All output pins low
   TRISB = $F0             ' Least significant 4 pins out, top 4 pins in
   IF ((PORTB >> 4) != $0F) Then gotkey ' If any keys down, loop
   key = (row * 4) + (NCD (col^$0F)) - 1 ' Combine row and column into numeric value
        
   ' Translate key to display label:
   ' 1  2  3  A
   ' 4  5  6  B
   ' 7  8  9  C
   ' *  0  #  D
   LookUp key,["123A456B789C*0#D"],disp_key
   Return                  ' Return to main loop

   End