/*
 * qaweep1.c - Quantron beeper-weeper demo V0.0.1
 *
 * Written by Roland Mainz <r.mainz@eckelmann.de>
 */

/*
 * Compile with
 * $ /opt/OSELAS.Toolchain-2012.12.0/arm-v5te-linux-gnueabi/gcc-4.7.2-glibc-2.16.0-binutils-2.22-kernel-3.6-sanitized/bin/arm-v5te-linux-gnueabi-gcc -std=gnu99 -g -Wall -fno-use-linker-plugin qaweep1.c
 */
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

#define NUM_ELEMENTS_IN_ARRAY(ar) (sizeof(ar) / sizeof (ar[0]))
const double freqs[] = {
	440.0000,
	466.1638,
	493.8833,
	523.2511,
	554.3653,
	587.3295,
	622.2540,
	659.2551,
	698.4565,
	739.9888,
	783.9909,
	830.6094,
	880.0000,
	932.3275,
	987.7666,
	1046.502,
	1108.731,
	1174.659,
	1244.508
};

#define MICROSECONDS_PER_SEC (1000000L)

static
int cycle_loop(int fd, long cycles, long low_delay, long high_delay)
{
	int retval = 0;
	int i;

	for (i = 0; i < cycles; i++) {
		if (write(fd, "1", 1) != 1) {
			goto exit_ioerr;
		}

		(void)usleep(low_delay);

		if (write(fd, "0", 1) != 1) {
			goto exit_ioerr;
		}

		(void)usleep(high_delay);
	}

	retval = 1;
exit_ioerr:

	return retval;
}

int main(int ac, char *av[])
{
	int	retval = EXIT_FAILURE;
	int	fd,
		gpiodirfd = -1;

	fd = open("/sys/class/gpio/export", O_WRONLY);
	if (fd == -1) {
		perror("Unable to open /sys/class/gpio/export");
		goto exit_ioerr;
	}

	if (write(fd, "11", 2) != 2) {
		perror("Error writing to /sys/class/gpio/export");
		goto exit_ioerr;
	}

	(void)close(fd);
    
	gpiodirfd = open("/sys/class/gpio/gpio11/", O_DIRECTORY);
	if (gpiodirfd == -1) {
		perror("Unable to open /sys/class/gpio/gpio11/");
		goto exit_ioerr;
	}

	fd = openat(gpiodirfd, "direction", O_WRONLY);
	if (fd == -1) {
		perror("Unable to open direction");
		goto exit_ioerr;
	}

	if (write(fd, "out", 3) != 3) {
		perror("Error writing to /sys/class/gpio/gpio11/direction");
		goto exit_ioerr;
	}

	(void)close(fd);

	fd = openat(gpiodirfd, "value", O_WRONLY);
	if (fd == -1) {
		perror("Unable to open value");
		goto exit_ioerr;
	}

	int j;
	for (j=0 ; j < NUM_ELEMENTS_IN_ARRAY(freqs) ; j++)
	{
		double f = freqs[j];
		long delay = ((double)(MICROSECONDS_PER_SEC))/f;
		long cycles = (100. * f) / 440.;
		
		(void)printf("freq=%4.4f\tdelay=%ld\tcycles=%ld\n",
			f,
			delay,
			cycles);
		
		if (!cycle_loop(fd, cycles, delay/2, delay/2))
		{
			perror("Error writing 0 to value");
			goto exit_ioerr;
		}

		/* Wait 1/4 second */
		(void)usleep(MICROSECONDS_PER_SEC/4);
	}

	(void)close(fd);

	fd = open("/sys/class/gpio/unexport", O_WRONLY);
	if (fd == -1) {
		perror("Unable to open /sys/class/gpio/unexport");
		goto exit_ioerr;
	}

	if (write(fd, "11", 2) != 2) {
		perror("Error writing to /sys/class/gpio/unexport");
		goto exit_ioerr;
	}
    
	retval = EXIT_SUCCESS;
exit_ioerr:
	if (fd >=0)
		(void)close(fd);
	if (gpiodirfd >=0)
		(void)close(gpiodirfd);

	return retval;
}