; keytest.asm
;
; 6-19-2001 Doug Ricket
; Microcontroller Project Lab
; Project 2, Part 1
;
; This program reads from a keypad on port 1 and 
; prints any keys pressed to the serial port.
;


main:
	acall serialinit
mainloop:
	acall 	get_char
	acall	sndchr
	sjmp 	mainloop

; KEYPAY PIN DEFINITIONS
keyport	equ	p1
col1	equ	p1.7
col2	equ	p1.6
col3	equ	p1.5
col4	equ	p1.4
row1	equ	p1.3
row2	equ	p1.2
row3	equ	p1.1
row4	equ	p1.0


; *************************
; Function: check_key 
;
; Checks for a key from a 4x4 matrix keypad
; Turns off each row, tests to see if any columns go off
; If so, a key is found, and the key number 1-16 is stored in A
; Otherwise, 0 is stored in A
; *************************

check_key:
	mov	keyport, #0FFh	; ready for input

	clr	row1		; Row 1
	mov	a, #01h
	jnb	col1, keyfound	; If col1 went low, then it connects to row1
	mov	a, #02h
	jnb	col2, keyfound
	mov	a, #03h
	jnb	col3, keyfound
	mov	a, #04h
	jnb	col4, keyfound
	setb	row1

	clr	row2		; Row 2
	mov	a, #05h
	jnb	col1, keyfound
	mov	a, #06h
	jnb	col2, keyfound
	mov	a, #07h
	jnb	col3, keyfound
	mov	a, #08h
	jnb	col4, keyfound
	setb	row2

	clr	row3		; Row 3
	mov	a, #09h
	jnb	col1, keyfound
	mov	a, #0Ah
	jnb	col2, keyfound
	mov	a, #0Bh
	jnb	col3, keyfound
	mov	a, #0Ch
	jnb	col4, keyfound
	setb	row3

	clr	row4		; Row 4
	mov	a, #0Dh
	jnb	col1, keyfound
	mov	a, #0Eh
	jnb	col2, keyfound
	mov	a, #0Fh
	jnb	col3, keyfound
	mov	a, #10h
	jnb	col4, keyfound
	setb	row4


	keynotfound:
	mov	a, #00h		; zero = no key pressed
	ret
	
	keyfound:		; a holds 1-16
	ret


; ************************
; Function: key_to_ascii
;
; Takes a key index 1-16 in A
; Returns the ascii code corresponding to that key in A
; ************************
key_to_ascii:			; Convert key code to ascii char
	movc a, @a+pc		; Lookup from the following table
	ret
	db	'1', '2', '3', 'A'
	db	'4', '5', '6', 'B'
	db	'7', '8', '9', 'C'
	db	'*', '0', '#', 'D'

; *************************
; wait_for_key_done
;
; Loops until no key is pressed
; *************************
wait_for_key_done:
	push	acc		; don't disturb the value in A
	wait_for_key_done_loop:
		acall	check_key		
		jnz	wait_for_key_done_loop
	pop	acc
	ret

; ********************
; get_key
; 
; Waits for a key to be pressed,
; Gets the key into A,
; Waits for the key to be released
; ********************
get_key:
	acall	check_key
	jz	get_key		; key == 0 means no key, so try again
	acall	wait_for_key_done
	ret


; **************
; get_char
;
; Waits for key press and release
; Returns ascii character for key
; **************
get_char:
	acall	get_key
	acall 	key_to_ascii
	ret
	
	


;=================================================================
; subroutine init
; this routine initializes the hardware
;=================================================================
serialinit:
; set up serial port with a 11.0592 MHz crystal,
; use timer 1 for 9600 baud serial communications (19200 for RD2)
   mov   tmod, #20h       ; set timer 1 for auto reload - mode 2
   mov   tcon, #41h       ; run counter 1 and set edge trig ints
   mov   th1,  #0fdh      ; set 9600 baud with xtal=11.059mhz
   mov   scon, #50h       ; set serial control reg for 8 bit data
                          ; and mode 1
   ret

;===============================================================
; subroutine sndchr
; this routine takes the chr in the acc and sends it out the
; serial port.
;===============================================================
sndchr:
   clr  scon.1            ; clear the tx  buffer full flag.
   mov  sbuf,a            ; put chr in sbuf
txloop:
   jnb  scon.1, txloop    ; wait till chr is sent
   ret