Audio Device Drivers

See include/nuttx/audio/audio.h for interface definitions. See also the audio subsystem at nuttx/audio/.

Audio Tone

This driver has an interfaces which accepts a PWM lower-half and a oneshot timer lower-half. Its features are enabled by CONFIG_AUDIO_TONE=y You can register a tone driver as follows:

#include <nuttx/audio/tone.h>
#include <nuttx/timers/pwm.h>

/* Somewhere later in the code */

int err;
struct pwm_lowerhalf_s *pwm;         /* Assume initialized */
struct oneshot_lowerhalf_s *oneshot; /* Assume initialized */

/* Here, the argument '1' is the PWM channel to use */

err = tone_register("/dev/tone0", pwm, 1, oneshot);
if (err < 0)
  {
    syslog(LOG_ERR, "Couldn't register /dev/tone0: %d\n", err);
  }

The PWM interface generates the tone output, and the one-shot driver is used to get the timing of musical notes correct.

If you want to try playing sound after the device is registered, you can write Music Macro Language (MML) to the character driver. For example, here is how you would play Ode to Joy:

nsh> echo "L8eefggfedccdeL6eL16dL4d" > /dev/tone0