.nolist
.include "m168def.inc"      ; Same family as 328P
.list


;; Interrupt Vector
.org 0x00
        rjmp        init

;; Syntax
.include "macros.inc"

;; SPI
.include "spi.inc"

;; Utils
.include "delay.inc"

;; Initialize output buffers
Main_Init:
    ; Setup ENable port
        sbi         PORTB, PORTB1 	    	; high -> disabled
        sbi         DDRB, PORTB1    		; out
 
	; all low
		ldi			r16, 0

		sts			spi_outbuf + 0, r16
		sts			spi_outbuf + 1, r16

	; write out
		rcall		SPI_SendRecv

	; enable
		cbi			PORTB, PORTB1			; low -> enabled

	; done
		ret

;; Scan through each pixel
Main_Scan:
	; init
		ldi			r18, 1
		ldi			r19, 1

scan_loop:
	; write out to SPI
		sts			spi_outbuf + 0, r18		; rows
		sts			spi_outbuf + 1, r19		; columns

		rcall		SPI_SendRecv

	; delay
		ldi			r20, 5					; ~4M cycles
		rcall		VarDelay

	; rows
		rol			r18						; next row
		brcc		scan_loop				; refresh if we didn't overflow
		
		rol			r18						; shift back from C into r20.0

	; cols
		rol			r19						; next col
		brcc		scan_loop				; refresh if we didn't overflow
		
		rol			r19						; shift back from C into r21.0

	; one scan completed
		ret

Main:
init:
    ; Stack
        ldi         r16, high(RAMEND)
        ldi         r17, low(RAMEND)
        out         SPH, r16
        out         SPL, r17

    ; Enable interrupts
        sei

    ; SPI
        rcall       SPI_Init
	

    ; Run
		rcall		Main_Init

loop:
		rcall		Main_Scan
		rjmp		loop

end:
        rjmp        end