LCD example

.include "m2560def.inc"

.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

.org 0
	jmp RESET


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

	ser r16
	out DDRF, r16
	out DDRA, r16
	clr r16
	out PORTF, r16
	out PORTA, r16

	do_lcd_command 0b00111000 ; 2x5x7
	rcall sleep_5ms
	do_lcd_command 0b00111000 ; 2x5x7
	rcall sleep_1ms
	do_lcd_command 0b00111000 ; 2x5x7
	do_lcd_command 0b00111000 ; 2x5x7
	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

	do_lcd_data 'H'
	do_lcd_data 'e'
	do_lcd_data 'l'
	do_lcd_data 'l'
	do_lcd_data 'o'

halt:
	rjmp halt

.equ LCD_RS = 7
.equ LCD_E = 6
.equ LCD_RW = 5
.equ LCD_BE = 4

.macro lcd_set
	sbi PORTA, @0
.endmacro
.macro lcd_clr
	cbi PORTA, @0
.endmacro

;
; Send a command to the LCD (r16)
;

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

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

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