drivers/sound/sound.c

   1 /*
   2  * Copyright (C) 2012 Samsung Electronics
   3  * R. Chandrasekar <rcsekar@samsung.com>
   4  *
   5  * SPDX-License-Identifier:     GPL-2.0+
   6  */
   7
   8 #include <common.h>
   9 #include <sound.h>
  10
  11 void sound_create_square_wave(unsigned short *data, int size, uint32_t freq)
  12 {
  13         const int sample = 48000;
  14         const unsigned short amplitude = 16000; /* between 1 and 32767 */
  15         const int period = freq ? sample / freq : 0;
  16         const int half = period / 2;
  17
  18         assert(freq);
  19
  20         /* Make sure we don't overflow our buffer */
  21         if (size % 2)
  22                 size--;
  23
  24         while (size) {
  25                 int i;
  26                 for (i = 0; size && i < half; i++) {
  27                         size -= 2;
  28                         *data++ = amplitude;
  29                         *data++ = amplitude;
  30                 }
  31                 for (i = 0; size && i < period - half; i++) {
  32                         size -= 2;
  33                         *data++ = -amplitude;
  34                         *data++ = -amplitude;
  35                 }
  36         }
  37 }