;
; hello7.lcd.asm
; Neil Gershenfeld CBA MIT 11/12/05
;

.include "tn13def.inc"
.def temp = R17			; temporary storage 
.def temp1 = R18		; temporary storage 
.def temp2 = R19		; temporary storage 
.def temp3 = R20		; temporary storage 

.equ E = PA3			; mapping the LCD pins to the AVR pins
.equ RS = PA1
.equ DB7 = PA7
.equ DB6 = PA6
.equ DB5 = PA5
.equ DB4 = PA4

		
.cseg
.org 0
rjmp reset

.equ delay_time = 100
delay:
	ldi temp3, delay_time
_delay1:
	ldi temp2, delay_time
_delay2:
	ldi temp1, delay_time
_delay3:
	dec temp1
	brne _delay3
	dec temp2
	brne _delay2
	dec temp3
	brne _delay1
	ret

lcd_tx:
	out PORTA, temp
	sbi PORTA, E
	nop
	nop
	nop
	nop
	nop
	nop
	nop
	cbi PORTA, E
	rcall delay
	ret
	
init_lcd:
	rcall delay		; hold off for a bit
	
	;; send the initialization sequence
	ldi temp, ( 1 << DB5 ) + ( 1 << DB4 )
	rcall lcd_tx
	rcall lcd_tx
	rcall lcd_tx

	;; function set command - 4-bit interface
	ldi temp, ( 1 << DB5 )
	rcall lcd_tx

	;; function set - two lines and 5x7 font
	ldi temp, ( 1 << DB5 )
	rcall lcd_tx
	ldi temp, ( 1 << DB7 )
	rcall lcd_tx

	;; display on/off
	clr temp
	rcall lcd_tx
	ldi temp, ( 1 << DB7 ) + ( 1 << DB6 ) + ( 1 << DB5 )
	rcall lcd_tx

	;; entry mode set
	clr temp
	rcall lcd_tx
	ldi temp, ( 1 << DB6 ) + ( 1 << DB5 )
	rcall lcd_tx

	ret
	
reset:
	ldi temp, 0xFF 		; maximum RC clock
	out OSCCAL, temp
	ldi temp, 0xDF
	out SP, temp 		; set the stack pointer to top of SRAM

	ldi temp, 0xFF		; make all of PORTA be outputs (for the LCD)
	out DDRA, temp
	
	rcall init_lcd		; initialise the LCD

	;; go to the zero position
	ldi temp, ( 1 << DB7 )
	rcall lcd_tx
	clr temp
	rcall lcd_tx

	;; transmit a character (H)
	ldi temp, ( 1 << DB6 ) + ( 1 << RS )
	rcall lcd_tx
	ldi temp, ( 1 << DB7 ) + ( 1 << RS )
	rcall lcd_tx

	;; transmit a character (E)
	ldi temp, ( 1 << DB6 ) + ( 1 << RS )
	rcall lcd_tx
	ldi temp, ( 1 << DB6 ) + ( 1 << DB4 ) + ( 1 << RS )
	rcall lcd_tx

	;; transmit a character (L)
	ldi temp, ( 1 << DB6 ) + ( 1 << RS )
	rcall lcd_tx
	ldi temp, ( 1 << DB7 ) + ( 1 << DB6 ) + ( 1 << RS )
	rcall lcd_tx

	;; transmit a character (L)
	ldi temp, ( 1 << DB6 ) + ( 1 << RS )
	rcall lcd_tx
	ldi temp, ( 1 << DB7 ) + ( 1 << DB6 ) + ( 1 << RS )
	rcall lcd_tx

	;; transmit a character (O)
	ldi temp, ( 1 << DB6 ) + ( 1 << RS )
	rcall lcd_tx
	ldi temp, ( 1 << DB7 ) + ( 1 << DB6 ) + ( 1 << DB5 ) + ( 1 << DB4 ) + ( 1 << RS )
	rcall lcd_tx

	;; move to the second line
	ldi temp, ( 1 << DB7 ) + ( 1 << DB6 )
	rcall lcd_tx
	clr temp
	rcall lcd_tx

	;; transmit a character (W)
	ldi temp, ( 1 << DB6 ) + ( 1 << DB4 ) + ( 1 << RS )
	rcall lcd_tx
	ldi temp, ( 1 << DB6 ) + ( 1 << DB5 ) + ( 1 << DB4 ) + ( 1 << RS )
	rcall lcd_tx
	
	;; transmit a character (O)
	ldi temp, ( 1 << DB6 ) + ( 1 << RS )
	rcall lcd_tx
	ldi temp, ( 1 << DB7 ) + ( 1 << DB6 ) + ( 1 << DB5 ) + ( 1 << DB4 ) + ( 1 << RS )
	rcall lcd_tx

	;; transmit a character (R)
	ldi temp, ( 1 << DB6 ) + ( 1 << DB4 ) + ( 1 << RS )
	rcall lcd_tx
	ldi temp, ( 1 << DB5 ) + ( 1 << RS )
	rcall lcd_tx

	;; transmit a character (L)
	ldi temp, ( 1 << DB6 ) + ( 1 << RS )
	rcall lcd_tx
	ldi temp, ( 1 << DB7 ) + ( 1 << DB6 ) + ( 1 << RS )
	rcall lcd_tx

	;; transmit a character (D)
	ldi temp, ( 1 << DB6 ) + ( 1 << RS )
	rcall lcd_tx
	ldi temp, ( 1 << DB6 ) + ( 1 << RS )
	rcall lcd_tx

main:
	rjmp main