The main.c file that demonstrates the bug

main.c (text/plain), 1.01 KB, created by Christopher Head on 2012-04-17 04:47:59 UTC

#define F_CPU 16000000L
#include <inttypes.h>
#include <stdio.h>
#include <avr/io.h>
#include <avr/pgmspace.h>
#include <util/delay.h>

static int serial_putchar(char ch, FILE *stream __attribute__((__unused__))) {
	// Wait until there's space in the hardware buffer to send the byte.
	while (!(UCSR0A & _BV(UDRE0)));

	// Queue the byte.
	UDR0 = ch;

	return 0;
}

static FILE serial_fp = FDEV_SETUP_STREAM(&serial_putchar, 0, _FDEV_SETUP_WRITE);

static void serial_init(void) {
	// Set to 9600 baud.
	UBRR0 = 103;
	UCSR0A = 0;

	// Wait for two byte times (20 / 9600 = 0.002 s) to let the transmit line settle high.
	_delay_ms(2);

	// Enable the transmitter.
	UCSR0B = _BV(TXEN0);

	// Set up the stream.
	stdout = &serial_fp;
}

uint8_t get_msb(void);
uint8_t get_lsb(void);

void main(void) __attribute__((__noreturn__));
void main(void) {
	uint8_t msb, lsb;
	uint16_t value;
	serial_init();

	for (;;) {
		msb = get_msb();
		lsb = get_lsb();
		value = (msb << 8) | lsb;
		printf("%" PRIX16 "\r\n", value);
		_delay_ms(1000);
	}
}