#include <avr/io.h>

.section .data

.section .bss
	lcdline:   .space 32    
	lcdptr:	   .space 1
	lcdcmd:    .space 1
	lcdoffset: .space 1
.section .text
.org 	0x00
.include "ivt.S"

LCDline: .ascii "EE308 Board v3.0"
	 .ascii "Keyboard ---->  "
LookUp:  .ascii "0123456789ABCDEF"

; LCD RS : PORTC<6>
; LCD EN : PORTC<4>
; LCD DATA : PORTA
; KBD DATA : PORTB<3:0>
; KBD DA : PORTB<4>

VOID:
	RETI

RESET:
	CALL	INIT_DISPLAY

LOOP: 

WAIT0:	
	LDS	R16, PINB
	SBRC	R16, 4
	RJMP	WAIT0
WAIT1:	
	LDS	R16, PINB
	SBRS	R16, 4
	RJMP	WAIT1
		
	LDI	ZL, lo8 (LookUp)
	LDI     ZH, hi8 (LookUp)
	LDS	R16, PINB
	LDI	R17, 0x0F
	AND	R16, R17
	LDI	R17, 0x00
	ADD	ZL, R16
	ADC	ZH, R17
	LPM	R16, Z
	
	LDI	R17, 0x1F
	LDI	R18, 0x00
	LDI	XL, lo8 (lcdline)	
	LDI     XH, hi8 (lcdline)	
	ADD	XL, R17
	ADC	XH, R18
	ST	X, R16
NO_KBD:	
        RJMP	LOOP



INIT_DISPLAY:
	LDI	ZL, lo8 (LCDline)
	LDI     ZH, hi8 (LCDline)
	LDI	XL, lo8 (lcdline)
	LDI     XH, hi8 (lcdline)	
	LDI	R17, 32
COPYLOOP:
	LPM	R16, Z+
	ST	X+, R16
	DEC	R17
	BRNE	COPYLOOP
			
	LDI	R16, 0x81
	OUT	_SFR_IO_ADDR (PORTB), R16
	OUT	_SFR_IO_ADDR (PORTC), R16
	LDI	R16, 0xFF
	OUT	_SFR_IO_ADDR (DDRA), R16
	OUT	_SFR_IO_ADDR (DDRC), R16
	LDI	R20, 250
	RCALL	DELAY_MS
	LDI	R20, 250
	RCALL	DELAY_MS
	
	LDI	R16, 0x38
	RCALL	WRITE_CMD
	LDI	R16, 0x0C
	RCALL	WRITE_CMD	
	LDI	R16, 0x01
	RCALL	WRITE_CMD
	LDI	R20, 2
	RCALL	DELAY_MS

	LDI	XL, lo8 (lcdline)
	LDI	XH, hi8 (lcdline)

	LDI	R16, 0x00
	STS	lcdptr, R16
	STS	lcdoffset, R16
	LDI	R16, 0xC0
	STS	lcdcmd, R16

	LDI	R16, (1<<CS02)|(1<<CS00)	; prescaler 1024
	STS	TCCR0B, R16	
	LDI	R18, (1<<TOIE0)			; enable timer overflow interrupt T0
	STS	TIMSK0, R18
	SEI					; enable interrupts	
	
	RET	; INIT_DISPLAY

TIMER0_OVF:
	PUSH	R16
	PUSH	R17
	PUSH	R18
	PUSH 	XL
	PUSH	XH
	IN	R18, _SFR_IO_ADDR (SREG)
	
	LDS	R16, lcdptr
	SBRC	R16, 4
	RJMP	SEND_LCD_CMD

	INC	R16
	STS	lcdptr, R16
	DEC	R16	
	SBI	_SFR_IO_ADDR (PORTC), 6
	LDS	R17, lcdoffset
	ADD	R16, R17
	LDI	R17, 0x00
	LDI	XL, lo8 (lcdline)	
	LDI     XH, hi8 (lcdline)	
	ADD	XL, R16
	ADC	XH, R17
	LD	R16, X
	STS	PORTA, R16
	RJMP	DONE_SEND_LCD_DATA
SEND_LCD_CMD:
	LDS	R16, 0x00
	STS	lcdptr, R16
	CBI	_SFR_IO_ADDR (PORTC), 6
	LDS	R16, lcdcmd
	STS	PORTA, R16
	LDI	R17, 0x40
	EOR	R16, R17
	STS	lcdcmd, R16
	LDS	R16, lcdoffset
	LDI	R17, 0x10
	EOR	R16, R17
	STS	lcdoffset, R16
DONE_SEND_LCD_DATA:
	SBI	_SFR_IO_ADDR (PORTC), 4
	NOP
	NOP
	NOP
	NOP
	CBI	_SFR_IO_ADDR (PORTC), 4
	
	OUT	_SFR_IO_ADDR (SREG), R18
	POP	XH
	POP	XL
	POP	R18
	POP	R17
	POP	R16	
	RETI



WRITE_CMD:
	CBI	_SFR_IO_ADDR (PORTC), 6
	RCALL	LCD_WRITE
	RET
WRITE_DATA:
	SBI	_SFR_IO_ADDR (PORTC), 6
	RCALL	LCD_WRITE
	RET
LCD_WRITE:	
	OUT	_SFR_IO_ADDR (PORTA), R16
	NOP
	SBI	_SFR_IO_ADDR (PORTC), 4
	LDI	R20, 1
	RCALL	DELAY_MS
	CBI	_SFR_IO_ADDR (PORTC), 4
	;LDI	R20, 2
	;RCALL	DELAY_MS		
	RET

DELAY_MS:
DELAY1:	LDI	R21, 16
DELAY2:	LDI	R22, 250
DELAY3:	DEC	R22
	NOP
        BRNE	DELAY3
        DEC	R21
        BRNE	DELAY2
        DEC	R20
        BRNE	DELAY1
        RET