Arduino wave shield - speed up - slow down demo from adafruit industries on Vimeo.

One of the reasons I made the Wave Shield kit is that I wanted to be able to play with audio clips and make strange effects. When every sample passes thru the Arduino, it becomes quite easy. For example, the Arduino has an interrupt that goes off 22,050 times a second (for 22kHz audio)…by simply changing the interrupt timing now you’ve changed the playback rate!

Here is the new code for the procedure that plays back the audio. Basically, it checks the analog pin and uses that value to generate a new sample rate scaled off of the original. Then it sets the new sample rate. There’s a little hysteresis code in there to make sure it only updates it when the pot is turned. As collin mentions, you can use any sort of analog sensor, such as a photo cell, bend sensor, etc!

int16_t lastpotval = 0;
#define HYSTERESIS 3

void playcomplete(char *name) {
  int16_t potval;
  uint32_t newsamplerate;

  playfile(name);
  while (wave.isplaying) {
     potval = analogRead(0);
     if ( ((potval - lastpotval) > HYSTERESIS) || ((lastpotval - potval) > HYSTERESIS)) {
        newsamplerate = wave.dwSamplesPerSec;  // get the original sample rate
        newsamplerate *= potval;                       // scale it by the analog value
        newsamplerate /= 512;   // we want to 'split' between 2x sped up and slowed down.
        wave.setSampleRate(newsamplerate);  // set it immediately!
        Serial.println(newsamplerate, DEC);  // for debugging
        lastpotval = potval;
     }
     delay(100);
   }
  card.close_file(f);
}

This entry was posted on Wednesday, May 21st, 2008 at 11:41 am and is filed under random. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.