int main() // main function
{
square_wave(26, 0, 10); // P26, ch0, 10 Hz.
pause(1000); // Pause 1 second
int cycles = count(26, 1000); // Count for 1 second
print("cycles = %d\n", cycles); // Report on/off cycles
// Negative pin clears signal and lets go of I/O pin.
square_wave(-26, 0, 0);
}
static void snd_callback(void *userdata, Uint8 * stream, int len)
{
static int lasttime;
static float lastfreq;
int i;
swsndupdate();
// lasttime stores the time offset from the last call
// we save the time so that the multiple time slices
// all fit together smoothly
// if we have changed frequency since last time, we need
// to adjust lasttime to the new frequency
lasttime *= (int)(lastfreq / current_freq);
for (i = 0; i < len; ++i) {
if (speaker_on) {
stream[i] =
127 * (int)square_wave(current_freq *
(i + lasttime));
} else {
stream[i] = 0;
}
}
lasttime += len;
lastfreq = current_freq;
}
/** This function gets the next audio sample **/
short SOUND_get_next_sample()
{
static short buffer;
//Do we have something to play?
if( current_note == SILENCE || current_note == EOT )
{
return wave_mode == TRIANGLE ? buffer : 0;
}
if( wave_mode == TRIANGLE ) buffer = triangle_wave();
if( wave_mode == SQUARE ) buffer = square_wave();
if( wave_mode == SAWTOOTH ) buffer = sawtooth_wave();
//No sound
return buffer;
}
