#define print_char(byte) {while((UCSR1A & 0b00100000) == 0) ; UDR1 = (byte); }

main()
{
ADMUX = 0b11010000;  // 2.56V reference, differential ADC0-ADC1  1x.
ADCSRB = 0b00000000; // free running mode
ADCSRA = 0b11101110; // prescaler = 64: 125 kHz. auto trigger.
DIDR0 = 0b00000011; // digi-inputtien disablointi ADC-kanavista

UBRR1 = 8; // 8 MHz 115200 bps, remember to use 2x
UCSR1A = 0b00000010; // 2x mode.
// 8 data bits, 1 stop bit, no parity bit
UCSR1C = 0b00000110;
// Enable RX and TX, but no interrupts.
UCSR1B = 0b00011000;
sei();
while(1);
}

ISR(ADC_vect)
{
	char buf[10];
	int16_t val = ADC;
	itoa(val, buf, 10);
	while(buf[0] != 0)
		print_char(buf[0]++);
	print_char(','); // erotinmerkiksi PC:lle
}