' Using the PIC16C620A PIC For a serial keypad encoder
' The keypad sends each key number entered out PortA.3
' serially, with PortA.4 acting as data-available pin.
' Dgood, [PortA.4] will remain high until key is released.
' Dgood will go low immediately after serial data is sent
' on Serpin [PortA.3]

define osc 4
include "bs2defs.bas"
cmcon 		= 	7 	  'Port A all I/O [dissable comparators].
dgood   	var   	porta.2	  'Data available pin. [high/low pulse on keypress]
serpin		var	porta.3	  'Serial output pin
baudin		var	porta.4	  'Baud rate selection pin. [can select on the fly]
nokey		con	%11111111 'No keys pressed
keyin		var	portb	  'Key input port on port B
keydata		var	byte
trisb 		= 	%11111111 'Port B = all inputs
trisa 		= 	%00010011 'A.0,A.1,A.4 inputs, rest are outputs
key1		var	portb.0
key2		var 	portb.1
key3		var	portb.2
key4		var	portb.3
key5		var	portb.4
key6		var	portb.5
key7		var	portb.6
key8		var	portb.7
key9		var	porta.0
key10		var	porta.1


'===========  Find the key pressed  ==========
findkey:
	if key1 = 0 then press1
	if key2 = 0 then press2
	if key3 = 0 then press3
	if key4 = 0 then press4
	if key5 = 0 then press5
	if key6 = 0 then press6
	if key7 = 0 then press7
	if key8 = 0 then press8
	if key9 = 0 then press9
	if key10 = 0 then press10
	goto findkey

'===========  Sort em out here  ==============

press1:
	keydata = 1
	goto dout
press2:
	keydata = 2
	goto dout
press3:
	keydata = 3
	goto dout
press4:
	keydata = 4
	goto dout
press5:
	keydata = 5
	goto dout
press6:
	keydata = 6
	goto dout
press7:
	keydata = 7
	goto dout
press8:
	keydata = 8
	goto dout
press9:
	keydata = 9
	goto dout
press10:
	keydata = 10
	goto dout
	
dout:
	low dgood		  'Pulse data good pin PortA.2.
	pause 100		  '100mS delay [software debounce].
wait1:
	if keyin <> nokey then wait1 'Wait for keys to be released.
wait2:
	if key9 = 0 then wait2
	if key10 = 0 then wait2

baudselect:
	if baudin = 1 then fast	   'If baudin=1 then N9600, else N2400
	serout serpin,N2400,[keydata] 'Send key value serially out PortA.3
	goto x2
fast:
	serout serpin,N9600,[keydata]
x2:
	high dgood
	keydata = %00000000	   'Clear data storage byte variable.
	goto findkey
end