$regfile = "2313def.dat"
$crystal = 4000000

$baud = 9600

Const Debouncetime = 150

Config Pind.6 = Output
Config Pind.2 = Input

Config Int0 = Falling
Dim Wtime As Byte
Dim Keycoderow As Byte
Dim Keycodecol As Byte
Dim Keycode As Byte
Dim Keychar As String * 1

On Int0 Button

'set upper nibble of portb to output, lower to input
Ddrb = &B11110000
Portb = &B00001111
Wtime = 255

Print "ready..."

Enable Interrupts
Enable Int0

Do
  Set Portd.6
  Waitms Wtime
  Reset Portd.6
  Waitms Wtime
Loop

Button:
  Waitms Debouncetime
  'read portb pins to determine which row is zero
  Keycoderow = Pinb
  'set portb upper nibble to input, lower to output
  Ddrb = &B00001111
  Portb = &B11110000
  'give port time to settle
  Waitms 1
  'read portb pins to determine which col is zero
  Keycodecol = Pinb
  'set portb back to original state
  Ddrb = &B11110000
  Portb = &B00001111
  'make keycode from portb pins read
  Select Case Keycoderow
    Case 7 : Keycode = 12
    Case 11 : Keycode = 8
    Case 13 : Keycode = 4
    Case 14 : Keycode = 0
    Case Else : Keycode = 99
  End Select
  'shift upper nibble to lower nibble
  Shift Keycodecol , Right , 4
  'make final keycode from portb pins read
  Select Case Keycodecol
    Case 7 : Keycode = Keycode + 3
    Case 11 : Keycode = Keycode + 2
    Case 13 : Keycode = Keycode + 1
    Case 14 : Keycode = Keycode + 0
    Case Else : Keycode = Keycode + 99
  End Select
  'illegal keycode from bounce effects
  If Keycode > 15 Then Keycode = 16
  Print Keycoderow ; " " ; Keycodecol ; " " ; Keycode
  Keychar = Lookupstr(keycode , Keycodes)
  Print Keychar
  Gifr = 64
Return

End

Keycodes:
Data "1" , "2" , "3" , "A" , "4" , "5" , "6" , "B" ,
Data "7" , "8" , "9" , "C" , "R" , "0" , "E" , "D" , "?"