/*
 * Q3.asm
 *
 *  Created: 12/10/2017 4:34:06 PM
 *   Author: Michael
 */


.include "m2560def.inc"

; Delay Constants
.equ F_CPU = 16000000
.equ DELAY_1MS = F_CPU / 4 / 1000 - 4 		; 4 cycles per iteration - setup/call-return overhead

; LCD Instructions
.equ LCD_RS = 7
.equ LCD_E = 6
.equ LCD_RW = 5
.equ LCD_BE = 4

.macro do_lcd_command
	ldi r16, @0
	rcall lcd_command
	rcall lcd_wait
.endmacro

.macro do_lcd_data
	ldi r16, @0
	rcall lcd_data
	rcall lcd_wait
.endmacro

.macro do_lcd_data_register
	mov r16, @0
	rcall lcd_data
	rcall lcd_wait
.endmacro

.macro lcd_set
	sbi PORTA, @0
.endmacro

.macro lcd_clr
	cbi PORTA, @0
.endmacro

.def row = r17						; current row number
.def col = r18						; current column number
.def rmask = r19					; mask for current row during scan
.def cmask = r20					; mask for current column during scan
.def temp1 = r21					; general use temp register
.def temp2 = r22					; general use temp register
.def temp3 = r23

.equ PORTLDIR = 0xF0				; PL7-4: output, PL3-0, input
.equ INITCOLMASK = 0xEF				; scan from the rightmost column,
.equ INITROWMASK = 0x01				; scan from the top row
.equ ROWMASK  = 0x0F				; for obtaining input from Port L

; Calculator
.def current = r0
.def sum = r2


.cseg
.org 0x0000
	jmp RESET
	jmp DEFAULT			; No handling for IRQ0
	jmp DEFAULT			; No handling for IRQ1

DEFAULT:
	reti

RESET:
	ldi r16, low(RAMEND)
	out SPL, r16
	ldi r16, high(RAMEND)
	out SPH, r16

	ser r16 						; set PORTF and PORTA to output
	out DDRF, r16
	out DDRA, r16
	clr r16
	out PORTF, r16
	out PORTA, r16

	ldi temp1, PORTLDIR				; columns are outputs, rows are inputs
	sts DDRL, temp1					; cannot use out

	do_lcd_command 0b00111000		; 2 lines of 5x7
	rcall sleep_5ms
	do_lcd_command 0b00111000		; 2 lines of 5x7
	rcall sleep_1ms
	do_lcd_command 0b00111000		; 2 lines of 5x7
	do_lcd_command 0b00111000		; 2 lines of 5x7
	do_lcd_command 0b00001000		; display off?
	do_lcd_command 0b00000001		; clear display
	do_lcd_command 0b00000110		; increment, no display shift
	do_lcd_command 0b00001110		; Cursor on, bar, no blink

	clr sum
	clr current

	rjmp main

main:
	ldi cmask, INITCOLMASK			; initial column mask
	clr col 						; initial column
	rjmp colloop

colloop:
	cpi col, 4 										; compare current column # to total # columns
	breq main										; if all keys are scanned, repeat
	sts PORTL, cmask								; otherwise, scan a column

	ldi temp1, 0xFF									; slow down the scan operation to debounce button press
	delay:
	rcall sleep_1ms
	dec temp1
	brne delay

	lds temp1, PINL									; read PORTL
	andi temp1, ROWMASK								; get the keypad output value
	cpi temp1, 0xF0 								; check if any row is low (0)
	breq colloop									; if yes, find which row is low
	ldi rmask, INITROWMASK							; initialize rmask with 0000 0001 for row check
	clr row

rowloop:
	cpi row, 4 										; compare current value of row with total number of rows (4)
	breq nextcol									; if theyre equal, the row scan is over.
	mov temp2, temp1 								; temp1 is 0xF
	and temp2, rmask 								; check un-masked bit
	breq convert 									; if bit is clear, the key is pressed
	inc row 										; else move to the next row
	lsl rmask 										; shift row mask left by one
	jmp rowloop

nextcol:											; if row scan is over
	lsl cmask 										; shift column mask left by one
	inc col 										; increase column value
	jmp colloop										; go to the next column

convert:
	cpi col, 3										; if the pressed key is in col.3
	breq letters									; we have a letter
	cpi row, 3										; if the key is not in col 3 and is in row3,
	breq symbols									; we have a symbol or 0
	mov temp1, row 									; otherwise we have a number in 1-9
	lsl temp1 										; multiply temp1 by 2
	add temp1, row 									; add row again to temp1 -> temp1 = row * 3
	add temp1, col 									; temp1 = col*3 + row
	inc temp1

number:
	ldi temp2, 10
	mul current, temp2
	add current, temp1
	subi temp1, -'0'
	do_lcd_data_register temp1
	jmp main

letters:
	cpi row, 2
	breq equals
	cpi row, 1
	breq subtraction
	cpi row, 0
	breq addition
	jmp main

symbols:
	cpi col, 1
	breq zero
	jmp main

equals:
	do_lcd_data '='
	jmp printResult
	jmp stop

stop:
	rjmp stop

addition:
	add sum, current
	clr current
	mov temp1, sum
	do_lcd_data '+'
	jmp main

subtraction:
	sub sum, current
	clr current
	mov temp1, sum
	do_lcd_data '-'
	jmp main

zero:
	ldi temp1, 0
	jmp number

lcd_command:
	out PORTF, r16
	rcall sleep_1ms
	lcd_set LCD_E
	rcall sleep_1ms
	lcd_clr LCD_E
	rcall sleep_1ms
	ret

lcd_data:
	out PORTF, r16
	lcd_set LCD_RS
	rcall sleep_1ms
	lcd_set LCD_E
	rcall sleep_1ms
	lcd_clr LCD_E
	rcall sleep_1ms
	lcd_clr LCD_RS
	ret

lcd_wait:
	push r16
	clr r16
	out DDRF, r16
	out PORTF, r16
	lcd_set LCD_RW
lcd_wait_loop:
	rcall sleep_1ms
	lcd_set LCD_E
	rcall sleep_1ms
	in r16, PINF
	lcd_clr LCD_E
	sbrc r16, 7
	rjmp lcd_wait_loop
	lcd_clr LCD_RW
	ser r16
	out DDRF, r16
	pop r16
	ret

sleep_1ms:
	push r24
	push r25
	ldi r25, high(DELAY_1MS)
	ldi r24, low(DELAY_1MS)
delayloop_1ms:
	sbiw r25:r24, 1
	brne delayloop_1ms
	pop r25
	pop r24
	ret

sleep_5ms:
	rcall sleep_1ms
	rcall sleep_1ms
	rcall sleep_1ms
	rcall sleep_1ms
	rcall sleep_1ms
	ret

sleep_25ms:
	rcall sleep_5ms
	rcall sleep_5ms
	rcall sleep_5ms
	rcall sleep_5ms
	rcall sleep_5ms
	ret


printResult:
	push temp2

    hundreds:
        clr temp2
        clr temp3

        hundredsCount:
			ldi temp1, 100
            cp sum, temp1
            brlo printHundreds

            ldi temp2, 100
            sub sum, temp2
            inc temp3
            jmp hundredsCount

        printHundreds:
            cpi temp3, 0
            breq tens

            subi temp3, -'0'
            do_lcd_data_register temp3

    tens:
        clr temp2
		clr temp3

        tensCount:
			ldi temp1, 10
            cp sum, temp1
            brlo printTens

            ldi temp2, 10
            sub sum, temp2
			inc temp3
            jmp tensCount

        printTens:
            subi temp3, -'0'
            do_lcd_data_register temp3

    ones:
		mov temp1, sum
        subi temp1, -'0'
	    do_lcd_data_register temp1

	epilogue:
	pop temp2
	rcall sleep_25ms
	ret