/*
 * lab1.asm
 *
 * This is a driver for the 12-digit keyboard used in "Laboration 1".
 * The purpose of this program is:
 *	-	To read what button is pressed on the keyboard.
 *	-	To display a corresponding binary value for that key on
 *		a simple LED-display.
 *
 * Authors:	Dennis Wildmark, Kalle Kellokoski Adamsson
 *
 * Date:	2014-11-11
 */

;==============================================================================
; Definitions of registers, etc. ("constants")
;==============================================================================
	.EQU RESET		= 0x0000 ; initializes constants and pointers
	.EQU PM_START	= 0x0056
	.DEF TEMP		= R16
	.DEF RVAL		= R24
	.EQU NO_KEY		= 0x0F
;==============================================================================
; Start of program
;==============================================================================
	.CSEG		;code segment starts here
	.ORG RESET
	RJMP init

	.ORG PM_START
	.INCLUDE "delay.inc"
	.INCLUDE "lcd.inc"
;==============================================================================
; Basic initializations of stack pointer, I/O pins, etc.
;==============================================================================
init:
	; Set stack pointer to point at the end of RAM.
	LDI TEMP, LOW(RAMEND)
	OUT SPL, TEMP
	LDI TEMP, HIGH(RAMEND)
	OUT SPH, TEMP
	; Initialize pins
	CALL init_pins
	CALL lcd_init
	; Initialize position for pressed key digit
	LDI RVAL, 0xC0
	RCALL lcd_write_instr
	; Jump to main part of program
	RJMP main

;==============================================================================
; Initialize I/O pins
;==============================================================================
init_pins:
	LDI TEMP, 0xF0	;initializes outputs PF4-7 and PB4-7
	OUT DDRF, TEMP
	OUT DDRB, TEMP
	LDI TEMP, 0xBF
	OUT DDRE, TEMP	;initializes input PE6
	LDI TEMP, 0xC0
	OUT DDRD, TEMP	;initializes outputs PD
	RET
;==============================================================================
; Read the keyboard and stuff
;==============================================================================
read_keyboard:
	LDI RVAL, 150
	RCALL delay_micros
	LDI R18, 0		; reset counter
scan_key:
	MOV R19, R18
	LSL R19			; moves bits in R19 4 steps to the left.
	LSL R19
	LSL R19
	LSL R19
	OUT PORTB, R19		; set column and row
	NOP			; a minimum of 20 NOP's is necessary to prevent propagation delay in multiplexer to interfere.
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	SBIC PINE, 6	; skips next instruction if PE6 is 0 (=not that key)
	RJMP return_key_val
	INC R18			; increments R18
	CPI R18, 12		; compares R18 to 12
	BRNE scan_key	; if R18 was not equal to 12, call scan_key again, else
	LDI R18, NO_KEY		; no key was pressed!
return_key_val:
	MOV RVAL, R18	; data in R18 is copied to RVAL
	RET
;==============================================================================
; Subroutines for the exeptions
;==============================================================================
char_a:
	LDI RVAL, 65
	RET
char_b:
	LDI RVAL, 66
	RET
;==============================================================================
; Convert keyboard output to ASCII-value
;==============================================================================
convert:
	LDI R18, 48
	ADD RVAL, R18	;ˆka RVAL med 48, vilket motsvarar v‰rdet i ASCII-tabellen
	CPI RVAL, 58	;om v‰rdet ‰r 58 (som ska vara
	BREQ char_a
	CPI RVAL, 59
	BREQ char_b
	RET
;==============================================================================
; Main part of program
;==============================================================================

main:
	LDI R24, 0xC0
	RCALL lcd_write_instr	;s‰tter markˆren i nedre v‰nstra hˆrnet

loop:
	RCALL read_keyboard		;l‰ser av keyboardet
	CPI RVAL, NO_KEY		;om ingen knapp trycks,
	BREQ loop				;hoppa tillbaka till loop
	MOV TEMP, RVAL			;kopiera RVAL till TEMP fˆr att j‰mfˆras senare
	RCALL convert			;talet konverteras
	RCALL lcd_write_chr		;det motsvarande ASCII-talet skrivs till displayen
	RCALL delay_keypressed	;stannar h‰r om samma knapp ‰r intryckt
	RJMP loop

delay_keypressed:
	RCALL read_keyboard		;tar reda p vilken knapp som ‰r intryckt
	CP TEMP, RVAL			;j‰mfˆr med fˆrra knappen som var intryckt
	BREQ delay_keypressed	;‰r det samma knapp, loopa
	RET