test VAR Byte
scan VAR Byte
key_in VAR Byte
number VAR Byte

main:
key_in=INB & 7      'mask bit3
scan=1
DO WHILE key_in<1
scan=scan<<1           'cycle output pins 0-3
IF scan>8 THEN  scan=1
OUTA=scan
key_in=INB & 7   'test for input
LOOP

GOSUB number_pressed

DO WHILE key_in >0
key_in=INB & 7        ' wait for key release, may need pause to allow for debounce
LOOP

GOTO main

number_pressed:
test.HIGHNIB=scan       'combine the nibbles
test.LOWNIB=key_in      'to test for which key is pressed
SELECT  test
CASE 17
number="1"
CASE 18
number="2"
CASE 20
number="3"
CASE 33
number="4"
CASE 34
number="5"
CASE 36
number="6"
CASE 65
number="7"
CASE 66
number="8"
CASE 68
number="9"
CASE 129
number="*"
CASE 130
number="0"
CASE 132
number="#"
ENDSELECT
RETURN 