Custom data capture by PDM microphone

[denko 2]

Hi,
I want custom data capture referred by the example pcm_capture,
I set to record one frame using one PDM microphone, but there is a ''attention and error'' then ''end'',
Could you please help me to check this?
Q1: why this attention happens?

Q2: I add an 'unsleep(10)' to wait for the recording so that the function execute_aframe might just execute once, but it does not work.

The whole code is below:

#include <Audio.h>

AudioClass *theAudio;

static const int32_t recoding_frames = 1;
static const int32_t buffer_size = 1540; /768sample,4ch,16bit, 6144 = 768 42 bytes/
static char s_buffer[buffer_size];

bool ErrEnd = false;

/**

• @brief Audio attention callback
• When audio internal error occurs, this function will be called back.
  */

void audio_attention_cb(const ErrorAttentionParam *atprm) {
puts("Attention!");

if (atprm->error_code >= AS_ATTENTION_CODE_WARNING) {
ErrEnd = true;
}
}

void setup() {
theAudio = AudioClass::getInstance();

theAudio->begin(audio_attention_cb);

puts("initialization Audio Library");

theAudio->initRecorder(AS_CODECTYPE_PCM, "/mnt/sd0/BIN", AS_SAMPLINGRATE_48000,AS_BITLENGTH_16, AS_CHANNEL_MONO);
puts("Init Recorder!");

puts("Rec!");
theAudio->startRecorder();
usleep(10);
}

/**

• @brief Audio signal process for your application
  */

void signal_process(uint32_t size) {
/* The actual signal processing will be coding here.
For example, prints capture data. */

printf("Size %ld [%02x %02x %02x %02x %02x %02x %02x %02x ...]\n",
size,
s_buffer[0],
s_buffer[1],
s_buffer[2],
s_buffer[3],
s_buffer[4],
s_buffer[5],
s_buffer[6],
s_buffer[7]);
}

/**

• @brief Execute frames for FIFO empty
  */

void execute_frames() {
uint32_t read_size = 0;
do {
err_t err = execute_aframe(&read_size);
if ((err != AUDIOLIB_ECODE_OK)
&& (err != AUDIOLIB_ECODE_INSUFFICIENT_BUFFER_AREA)) {
break;
}
} while (read_size > 0);
}

/**

• @brief Execute one frame
  */

err_t execute_aframe(uint32_t *size) {
printf("before Size %ld \n", *size);
err_t err = theAudio->readFrames(s_buffer, buffer_size, size);
printf("after Size %ld \n", *size);
if (((err == AUDIOLIB_ECODE_OK) || (err == AUDIOLIB_ECODE_INSUFFICIENT_BUFFER_AREA)) && (*size > 0)) {
signal_process(*size);
}

return err;
}

/**

• @brief Capture frames of PCM data into buffer
  */
  void loop() {

static int32_t total_size = 0;
uint32_t read_size = 0;

/* Execute audio data */
err_t err = execute_aframe(&read_size);
if (err != AUDIOLIB_ECODE_OK && err != AUDIOLIB_ECODE_INSUFFICIENT_BUFFER_AREA) {
theAudio->stopRecorder();
goto exitRecording;
} else if (read_size > 0) {
total_size += read_size;
}

/* This sleep is adjusted by the time to write the audio stream file.

• Please adjust in according with the processing contents
• being processed at the same time by Application.
• The usleep() function suspends execution of the calling thread for usec
• microseconds. But the timer resolution depends on the OS system tick time
• which is 10 milliseconds (10,000 microseconds) by default. Therefore,
• it will sleep for a longer time than the time requested here.
  */

// usleep(10000);

/* Stop Recording */
if (total_size > (recoding_frames * buffer_size)) {
theAudio->stopRecorder();

/* Get ramaining data(flushing) */
sleep(1); /* For data pipline stop */
execute_frames();

goto exitRecording;

}

if (ErrEnd) {
printf("Error End\n");
theAudio->stopRecorder();
goto exitRecording;
}

return;

exitRecording:

theAudio->setReadyMode();
theAudio->end();

puts("End Recording");
exit(1);
}

\code end

Results in Serial monitor:

without writing for 'size':

[CamilaSouza]

Hi @denko-2

Thank you for using the forum for your technical questions.
I'll analyse your question and get back to you as soon as possible

[dshilov 1 1]

@denko-2
Line 84 of the audio_recorder_sink.cpp mentions the following word AS_ATTENTION_SUB_CODE_SIMPLE_FIFO_OVERFLOW which indicates your buffer (FIFO) size for storing audio data is too small. Try to increase your recording_frames to 5 and buffer_size to 3x what you have now.

[CamilaSouza]

Good catch, @dshilov-1-1

[denko 2]

@dshilov-1-1
Thanks very much for your reply.

Do you know how we can change the sample per frame in 'pcm capture' example? I find it fixed at 768.

[dshilov 1 1]

@denko-2 If I recall correctly, the samples per frame are used only when pulling data out of FIFO and for setting total FIFO size (number of frames * frame size), and should be adapted for optimum performance for your application.

Change the variable SIMPLE_FIFO_READ_SIZE.

[denko 2]

@dshilov-1-1 Thanks very much for your detailed answer.