.nolist
.include "m16def.inc"
.list
;Serial communication
;Send the byte read from switches out the serial port
;Display received bytes (serial) on LEDS

;communication parameters 

;(frame format)
;select bit (1) (required to write to this control register)
;asynchronous mode (0)
;parity odd (11)
;stop bits one (0)
;# data bits 8 (11)
ldi r16, (1<<URSEL)|(0<<UMSEL)	\
		|(0b11<<UPM0)|(0<<USBS)	\
		|(0b11<<UCSZ0)
;ldi r16, 0b10110110
out UCSRC, r16

;Baud rate 1 MHz clock, 2400 baud
.equ BRP = 25 ;0.2% error
ldi r16, high(BRP)
out UBRRH, r16
ldi r16, low(BRP)
out UBRRL, r16

;turn it on!
;in r17, UCSRB
ldi r16, (1<<RXEN)|(1<<TXEN)
;             4         3
;        00010000 | 00001000 = 00011000
;or r16, r17
out UCSRB, r16

;sbi UCSRB, RXEN
;sbi UCSRB, TXEN

ldi r16, 0
out DDRA, r16

ldi r16, $FF
out PORTB, r16
out DDRB, r16

lp:
	in r16, PINA
	cpi r16, $FF
	breq nonepressed
	com r16
	;transmit the switch pattern
	sbic UCSRA, UDRE
	out UDR, r16	;only if transmit Q empty
nonepressed:	
	;check receive Q
	sbis UCSRA, RXC
	rjmp lp ;nothing in Q
	;copy received byte to LEDs
	in r16, UDR
	com r16
	out PORTB, r16
	rjmp lp