<alp/audio.h> — PDM In + I²S Out

Microphone capture, speaker playback, and the ALP-default DSP chain.

Header

#include <alp/audio.h>

Capture (PDM microphone)

alp_audio_in_t *mic = alp_audio_in_open(&(alp_audio_in_config_t){
    .source       = ALP_AUDIO_SRC_PDM,
    .sample_rate_hz = 16000,
    .channels       = 1,
    .bit_depth      = 16,
});

int16_t samples[1024];
size_t got;
alp_audio_in_read(mic, samples, sizeof(samples)/sizeof(samples[0]), &got);

alp_audio_in_close(mic);

Playback (I²S speaker)

alp_audio_out_t *spkr = alp_audio_out_open(&(alp_audio_out_config_t){
    .sink         = ALP_AUDIO_SINK_I2S,
    .sample_rate_hz = 44100,
    .channels       = 2,
    .bit_depth      = 16,
});

alp_audio_out_set_volume(spkr, 80);   // 0..100 (software linear scale on Yocto)
alp_audio_out_write(spkr, pcm_buffer, n_frames);

Backends

Backend	Implementation
Zephyr	I²S subsystem + PDM controller driver.
Yocto	ALSA (snd_pcm_*). peripheral_id == 0 → "default"; peripheral_id == N → "hw:N-1,0".
Bare-metal	Vendor HAL.

The application API is identical across backends.

ALP default DSP chain

alp_audio_in_open installs an ALP-default chain (high-pass + AGC + noise gate) when no custom chain is provided. Pass your own <alp/dsp.h> chain to override.

See also

• <alp/dsp.h> — FIR/IIR/FFT chains
• <alp/i2s.h> — raw I²S