drivers/sound/sound.c

/*
 * Copyright (C) 2012 Samsung Electronics
 * R. Chandrasekar <rcsekar@samsung.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 * MA 02111-1307 USA
 */

#include <common.h>
#include <sound.h>

void sound_create_square_wave(unsigned short *data, int size, uint32_t freq)
{
	const int sample = 48000;
	const unsigned short amplitude = 16000; /* between 1 and 32767 */
	const int period = freq ? sample / freq : 0;
	const int half = period / 2;

	assert(freq);

	/* Make sure we don't overflow our buffer */
	if (size % 2)
		size--;

	while (size) {
		int i;
		for (i = 0; size && i < half; i++) {
			size -= 2;
			*data++ = amplitude;
			*data++ = amplitude;
		}
		for (i = 0; size && i < period - half; i++) {
			size -= 2;
			*data++ = -amplitude;
			*data++ = -amplitude;
		}
	}
}