.include "m16def.inc"

.equ UBBRvalue = 25 ;1MHz 2400 baud
ldi r16, low(UBBRvalue)
ldi r17, high(UBBRvalue)
out UBRRH, r17
out UBRRL, r16
;async, odd parity, 1 stop bit, 8 data bits
ldi r16, 1<<URSEL | 3<<UPM0 | 0<<USBS | 3<<UCSZ0
out UCSRC, r16

ldi r16, 1<<RXEN | 1<<TXEN
out UCSRB, r16

;USART is active
;switches connected on PORTA
clr r16
out DDRA, r16

;LED's on PORTB
ldi r16, $FF
out PORTB, r16
out DDRB, r16

lp:
	in r16, PINA
	cpi r16, $FF
	breq nonepressed

	;a switch is pressed
	;output if room in Q, skip UDRE=0
	sbic UCSRA, UDRE
	out UDR, r16

nonepressed:
	in r16, UCSRA
	andi r16, 1<<RXC
	breq lp

	;a byte is waiting...
	in r16, UDR
	out PORTB, r16
	rjmp lp