Microphone#
Sound level driver for PDM and I2S microphones.
Microphone example code#
Basic example for looping measurement of sound level:
#include "sl_mic.h"
#define MIC_SAMPLE_RATE 44100
#define MIC_SAMPLE_BUFFER_SIZE 1024
#define MIC_N_CHANNELS 2
static int16_t buffer[MIC_SAMPLE_BUFFER_SIZE * MIC_N_CHANNELS];
int main( void )
{
...
float sound_level_0;
float sound_level_1;
uint32_t n_samples = 1024;
// Initialize microphone with sample rate and number of channels
sl_mic_init(MIC_SAMPLE_RATE, MIC_N_CHANNELS);
while(true){
// Read samples from the microphone
sl_mic_get_n_samples(buffer, n_samples);
while (!sl_mic_sample_buffer_ready()) {
// Wait until sample buffer ready
}
// Calculate sound level
sl_mic_calculate_sound_level(&sound_level_0, buffer, n_samples, 0);
sl_mic_calculate_sound_level(&sound_level_1, buffer, n_samples, 1);
}
...
} Typedefs#
Callback function indicating that the sample buffer is ready.
Functions#
Initialize the microphone.
De-initialize the microphone.
Read samples from the microphone into a sample buffer.
Read samples from the microphone into a sample buffer continuously.
Start the microphone.
Stop the microphone.
Check whether the sample buffer is ready.
Calculate the dBSPL value for a channel from a sample buffer.
Typedef Documentation#
sl_mic_buffer_ready_callback_t#
typedef void(* sl_mic_buffer_ready_callback_t) (const void *buffer, uint32_t n_frames) )(const void *buffer, uint32_t n_frames)
Callback function indicating that the sample buffer is ready.
| [in] | buffer | Pointer to the sample buffer. |
| [in] | n_frames | Number of audio frames in the sample buffer. |
Returns
None.
103 of file hardware/driver/mic/inc/sl_mic.hFunction Documentation#
sl_mic_init#
sl_status_t sl_mic_init (uint32_t sample_rate, uint8_t channels)
Initialize the microphone.
| [in] | sample_rate | The desired sample rate in Hz |
| [in] | channels | Number of audio channels (1 or 2) |
Returns
Returns SL_STATUS_OK on success, non-zero otherwise
118 of file hardware/driver/mic/inc/sl_mic.hsl_mic_deinit#
sl_status_t sl_mic_deinit (void )
De-initialize the microphone.
| N/A |
126 of file hardware/driver/mic/inc/sl_mic.hsl_mic_get_n_samples#
sl_status_t sl_mic_get_n_samples (void * buffer, uint32_t n_frames)
Read samples from the microphone into a sample buffer.
| [in] | buffer | Pointer to the sample buffer to store the data. 16-bit channel data is stored consecutively, starting with ch0 |
| [in] | n_frames | The number of the audio frames to get |
This function starts the microphone sampling and stops the sampling after reading the desired number of samples. Call sl_mic_sample_buffer_ready to check when the samples are ready in the buffer.
148 of file hardware/driver/mic/inc/sl_mic.hsl_mic_start_streaming#
sl_status_t sl_mic_start_streaming (void * buffer, uint32_t n_frames, sl_mic_buffer_ready_callback_t callback)
Read samples from the microphone into a sample buffer continuously.
| [in] | buffer | Pointer to the sample buffer to store the data. 16-bit channel data is stored consecutively, starting with ch0. This buffer shall be big enough to hold twice the n_frames because of the ping-pong operation. |
| [in] | n_frames | The number of audio frames to receive before the callback is called. Maximum value limited by DMADRV_MAX_XFER_COUNT. |
| [in] | callback | Callback is called when n_frames in the sample buffer is ready. |
This function starts the microphone sampling and stops only upon calling sl_mic_stop or sl_mic_deinit. The buffer is used in a "ping-pong" manner meaning that one half of the buffer is used for sampling while the other half is being processed.
178 of file hardware/driver/mic/inc/sl_mic.hsl_mic_start#
sl_status_t sl_mic_start (void )
Start the microphone.
| N/A |
188 of file hardware/driver/mic/inc/sl_mic.hsl_mic_stop#
sl_status_t sl_mic_stop (void )
Stop the microphone.
| N/A |
197 of file hardware/driver/mic/inc/sl_mic.hsl_mic_sample_buffer_ready#
bool sl_mic_sample_buffer_ready (void )
Check whether the sample buffer is ready.
| N/A |
206 of file hardware/driver/mic/inc/sl_mic.hsl_mic_calculate_sound_level#
sl_status_t sl_mic_calculate_sound_level (float * sound_level, const int16_t * buffer, uint32_t n_frames, uint8_t channel)
Calculate the dBSPL value for a channel from a sample buffer.
| [out] | sound_level | The calculated sound level |
| [in] | buffer | Buffer to calculate sound level from. Must contain 16-bit samples, starting with channel 0 |
| [in] | n_frames | Number of audio frames to use when calculating sound level |
| [in] | channel | The channel to get the sound level for |
228 of file hardware/driver/mic/inc/sl_mic.h