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This commit adds some documentation about the audio tone driver, how to use it and links to it from the main audio component page. I also added some back links to other audio docs there for convenience. Signed-off-by: Matteo Golin <matteo.golin@gmail.com>
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====================
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Audio Device Drivers
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====================
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See ``include/nuttx/audio/audio.h`` for interface definitions.
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See also the audio subsystem at ``nuttx/audio/``.
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Audio Tone
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----------
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This driver has an interfaces which accepts a PWM lower-half and a oneshot timer
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lower-half. Its features are enabled by ``CONFIG_AUDIO_TONE=y`` You can register
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a tone driver as follows:
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.. code:: c
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#include <nuttx/audio/tone.h>
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#include <nuttx/timers/pwm.h>
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/* Somewhere later in the code */
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int err;
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struct pwm_lowerhalf_s *pwm; /* Assume initialized */
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struct oneshot_lowerhalf_s *oneshot; /* Assume initialized */
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/* Here, the argument '1' is the PWM channel to use */
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err = tone_register("/dev/tone0", pwm, 1, oneshot);
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if (err < 0)
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{
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syslog(LOG_ERR, "Couldn't register /dev/tone0: %d\n", err);
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}
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The PWM interface generates the tone output, and the one-shot driver is used to
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get the timing of musical notes correct.
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If you want to try playing sound after the device is registered, you can write
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`Music Macro Language (MML)
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<https://en.wikipedia.org/wiki/Music_Macro_Language>`_ to the character driver.
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For example, here is how you would play Ode to Joy:
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.. code:: console
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nsh> echo "L8eefggfedccdeL6eL16dL4d" > /dev/tone0
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