Samplerates of multiple audio inputs of the Audio Expander

Bethanychm

I have enabled 4 analog inputs of the audio expander as audio inputs. I want to use 4 microphones (Type: Breakout Board for ADMP401 MEMS Microphone) to record the background noise at 44.1KHz sampling rate. The results were strange: when I set the Analog Sample Rate at 44100Hz, there are only 2 mics collects the noise while the others fail, but when I set the Analog Sample Rate at 22050Hz, all 4 mics can record the noise. I will upload the IDE seetings and the code. Please help to point out what my problem is?

Sample Rate = 22050Hz:

int mics = 4;
float input1,input2,input3,input4;
int gAudionperAnalog;
Scope scope;

bool setup(BelaContext* context, void* userData)
{
  printf("Audio Sample Rate: %f\n", context->audioSampleRate);
  printf("Audio Frames: %d\n", context->audioFrames);
  printf("Audio Output Channels: %d\n", context->audioOutChannels);
  printf("Audio Input Channels: %d\n", context->audioInChannels);
  
  printf("Analog Sample Rate: %f\n", context->analogSampleRate);
  printf("Analog Frames: %d\n", context->analogFrames);
  printf("Analog Output Channels: %d\n", context->analogOutChannels);
  printf("Analog Input Channels: %d\n", context->analogInChannels);
  
  gAudionperAnalog = context->audioFrames/context->analogFrames;
  printf("Audio/Analog Frames: %d\n", gAudionperAnalog);
  
  scope.setup(mics,context->audioSampleRate);
  return true;
}

void render(BelaContext* context, void* userData)
{

  for(unsigned int n = 0; n < context->audioFrames; ++n)
  {
	    
	    if((n%2) == 0){
	    	    input1 = analogRead(context, n/gAudionperAnalog, 3);
		    input2 = analogRead(context, n/gAudionperAnalog, 5);
		    input3 = analogRead(context, n/gAudionperAnalog, 6);
		    input4 = analogRead(context, n/gAudionperAnalog, 7);
	    }
	    
	    scope.log(input1,input2,input3,input4);

  }
  
}

void cleanup(BelaContext *context, void *userData) {
	
}

Sample Rate = 44100Hz:

bool setup(BelaContext* context, void* userData)
{
  # same as the 22050Hz
}

void render(BelaContext* context, void* userData)
{

  for(unsigned int n = 0; n < context->audioFrames; ++n)
  {
	   input1 = analogRead(context, n/gAudionperAnalog, 3);
           input2 = analogRead(context, n/gAudionperAnalog, 5);
	   input3 = analogRead(context, n/gAudionperAnalog, 6);
           input4 = analogRead(context, n/gAudionperAnalog, 7);
	    
	   scope.log(input1,input2,input3,input4);

  }
  
}

void cleanup(BelaContext *context, void *userData) {
	
}

giuliomoro

When the sampling rate of the analogs is set to 44100 reading from channels >=4 is illegal. You have connected your signals to channels 3, 5, 6, 7. You should use 0, 1, 2, 3 instead.

Bethanychm

giuliomoro Thank you very much! 😄 I solved it with using channels 0-3 at the sampling rate to 44100Hz.

Bethanychm

Hi, giuliomoro! I have one more query. I connect the speaker (general-purpose EARISE AL-202 speaker, "Audio Out" on cape) and 4 microphones to the Bela platform and leverage the FMCW acoustic signals to measure the AoA between the target and the pair of the speaker and microphones. How should I arrange the sequence of audio out and analog in? And how about the recording of signals both for output and input?
For example, I have two types of code forms：

First, audio output and analog inputs are within one frame

#include <Bela.h>
#include <libraries/AudioFile/AudioFile.h>
#include <libraries/Scope/Scope.h>
#include <vector>
#include <libraries/WriteFile/WriteFile.h>

WriteFile trans_sw;
WriteFile rece_sw;

// FMCW
int Fc = 16000; // start frequency
int B = 4000;  	// bandwith
float T = 0.1;	// sweep time
float t_mod = 0.0;
float gInverseSampleRate;

bool setup(BelaContext *context, void *userData)
{
	gInverseSampleRate = 1.0 / context->audioSampleRate;

        // Check that we have the same samplerates of audio and analog.
	if(context->audioFrames != context->analogFrames )
        {
	printf("Error: for this project, you need the same samplerates of audio and analog frames.\n");
        }

        trans_sw.setup("trans_f.bin"); //set the file name to write to
	trans_sw.setFileType(kBinary);
	trans_sw.setFormat("binary: %.4f\n");

	rece_sw.setup("rece_f.bin");
	rece_sw.setFileType(kBinary);
	rece_sw.setFormat("binary: %.4f %.4f %.4f %.4f\n");

        return true;
}

void render(BelaContext *context, void *userData)
{
	for(unsigned int n = 0; n < context->audioFrames; n++) {
    	        if(t_mod >= T)
			t_mod = 0.0;
			
		float gPhase = Fc*t_mod + B*pow(t_mod,2)/(2*T);
		float out = 10.0f * cos(2.0f * (float)M_PI * gPhase);
		t_mod += gInverseSampleRate;

		for(unsigned int ch = 0; ch < context->audioOutChannels; ch++) {
			audioWrite(context, n, ch, out);
		}
                
                trans_sw.log(out);

               for(unsigned int ch = 0; ch < context->analogInChannels; ch++) {
                    float val =  analogRead(context, n, ch);
                    rece_sw.log(val);
               }
	}
}

void cleanup(BelaContext *context, void *userData)
{
}

Second, audio output and analog inputs are within differnt frames

void render(BelaContext *context, void *userData)
{
	for(unsigned int n = 0; n < context->audioFrames; n++) {
    	        if(t_mod >= T)
			t_mod = 0.0;
			
		float gPhase = Fc*t_mod + B*pow(t_mod,2)/(2*T);
		float out = 10.0f * cos(2.0f * (float)M_PI * gPhase);
		t_mod += gInverseSampleRate;

		for(unsigned int ch = 0; ch < context->audioOutChannels; ch++) {
			audioWrite(context, n, ch, out);
		}
                
                trans_sw.log(out);

	}

        for(unsigned int n = 0; n < context->analogFrames; n++){
               for(unsigned int ch = 0; ch < context->analogInChannels; ch++) {
                     float val =  analogRead(context, n, ch);
                     rece_sw.log(val);
               }
         }

}

Can you give me some advice or point out some mistakes in my code? Thanks!

giuliomoro

Bethanychm for(unsigned int n = 0; n < context->analogFrames; n++){
for(unsigned int ch = 0; ch < context->analogInChannels; ch++ {
float val = analogRead(context, n, ch);
rece_sw.log(val);
}
}

this loop should not be contained in the outer loop for(unsigned int n = 0; n < context->audioFrames; n++) { as it currently is

Bethanychm

giuliomoro Sorry for my mistake! I have edited the second piece of code. So the correct way is the second one that the audio should be sent out block by block rather than frame by frame? Or the two types of code forms are both ok?

giuliomoro

the code above logs the out variable context->audioFrames times and then it logs the analog input value from each analog channel for each analog frame.

Bethanychm

giuliomoro
Hi! I haven't used Bela for 2 years, and I am still a noob for using Bela. Recently, I want to use 4 mics to measure AoA for the reflected acoustic signals, as descirbed in this discussion before. When I start using the "Analog Input 0-3" of the Audio Expander Capelet as audio input, it seems that only channels 2-3 can receive signals normally, while channels 0-1 cannot work properly. Is there something wrong with pin 0-1?

Here is the testing code for the "Analog Input 0-3" of the audio expansion module:

#include <Bela.h>
#include <libraries/Scope/Scope.h>

float gFrequency = 2000;
float gAmplitude = 1.0;		// Amplitude of the sine wave (1.0 is maximum)
unsigned int gTotalSamples = 0;
float gPhase; 
float gInverseSampleRate;

int mics = 4;
float input1,input2,input3,input4;
int gAudioFramesPerAnalogFrame;
Scope scope;

bool setup(BelaContext* context, void* userData)
{
  printf("Audio Sample Rate: %f\n", context->audioSampleRate);
  printf("Audio Frames: %d\n", context->audioFrames);
  printf("Audio Output Channels: %d\n", context->audioOutChannels);
  printf("Audio Input Channels: %d\n", context->audioInChannels);
  
  printf("Analog Sample Rate: %f\n", context->analogSampleRate);
  printf("Analog Frames: %d\n", context->analogFrames);
  printf("Analog Output Channels: %d\n", context->analogOutChannels);
  printf("Analog Input Channels: %d\n", context->analogInChannels);
  
  gAudioFramesPerAnalogFrame = context->audioFrames/context->analogFrames;
  printf("Audio/Analog Frames: %d\n", gAudioFramesPerAnalogFrame);
  
  gInverseSampleRate = 1.0 / context->audioSampleRate;
  
  scope.setup(mics,context->audioSampleRate);
  return true;
}

void render(BelaContext* context, void* userData)
{

  for(unsigned int n = 0; n < context->audioFrames; ++n)
  {
  	gPhase += 2.0 * M_PI * gFrequency * gInverseSampleRate;
	if (gPhase >= 2.0 * M_PI)
		gPhase -= 2.0 * M_PI;
  		
  	float out = gAmplitude * sin(gPhase);
  		
       for (unsigned int ch = 0; ch < context->audioOutChannels; ch++){
	    	audioWrite(context, n, ch, out);
        }

        input1 = analogRead(context, n/gAudioFramesPerAnalogFrame, 0);
        input2 = analogRead(context, n/gAudioFramesPerAnalogFrame, 1);
        input3 = analogRead(context, n/gAudioFramesPerAnalogFrame, 2);
        input4 = analogRead(context, n/gAudioFramesPerAnalogFrame, 3);

        scope.log(input1,input2,input3,input4);

  }
  
}

void cleanup(BelaContext *context, void *userData) {
	
}

The Oscilloscope window shows as:

The system setting is:

giuliomoro

On the audio expander capelet you need a jumper wire on each channel you want to enable, see https://learn.bela.io/products/accessories/audio-expander/#using-jumper-wires-to-change-the-expanders-function

Do you have those jumpers in place?

Bethanychm

giuliomoro Yes, I have put the jumpers in place of J10、J11 and J12 for all 8 channels.

Bethanychm

giuliomoro Could you please tell me how to troubleshoot the problem with pin0-1?

giuliomoro

I can't see much of the wiring there, can you try showing a closeup of the input sockets? I can't see where the yellow and orange wires go . Also, it's always a good idea to try a different wire , try getting that signal from a different place (e.g.: swap orange/yellow with green/gray: what happens?) etc

Bethanychm

giuliomoro Sure! I tried to change different wires, but it seems that there is no change. Below are the figures:

Please help check!

giuliomoro

Do IN-2 and IN-3 in the scope screenshot respond to changes in the input sound ? What about IN-0 and IN-1, do they respond but are quieter, or do they not respond at all?

I would try swapping on the breadboad yellow with brown and blue with green: what happens to the scope then?

Bethanychm

giuliomoro Yes, IN-2 and IN-3 in the scope screenshot respond to changes in the input sound ,and IN-0 and IN-1 respond but are quieter, the scope shows as blow:

Following your suggestion, I try to swap on the breadboad yellow with brown and blue with green, the results are blow:

IN-0 and IN-1 always respond quieter.

giuliomoro

Can you:

make sure the expander board is firmly pressed against the Bela cape
replace the gain-setting jumper wires on J12 for channels 0 and 1
replace the enabling jumper wires on J10 and J11 for channels 0 and 1

and see if anything improves?

Bethanychm

giuliomoro I checked your 3 points, but there was no improvement.

giuliomoro

Can you set the number of analog inputs to 8 and look at all 8 inputs by moving a the same signal through each of them, one at a time?

Bethanychm

giuliomoro Do you mean that I should check the inputs of analog0-7 one by one?
For example, the code in render() changes to:

int gAudioperAnalog = context->audioFrames/context->analogFrames;
void render(BelaContext* context, void* userData)
{

  for(unsigned int n = 0; n < context->audioFrames; ++n)
  {
  		gPhase += 2.0 * M_PI * gFrequency * gInverseSampleRate;
		if (gPhase >= 2.0 * M_PI)
			gPhase -= 2.0 * M_PI;
  		
  		float out = gAmplitude * sin(gPhase);
  		
	    for (unsigned int ch = 0; ch < context->audioOutChannels; ch++){
	    	audioWrite(context, n, ch, out);
	    }
	    
	  if((n%2) == 0){
	    	input = analogRead(context, n/gAudioFramesPerAnalogFrame, 0);  % analog input channel test from IN 0-7
	  }
    	scope.log(input);

  }
  
}

Is my understanding correct?

Bethanychm

giuliomoro Following my understanding, when I output the same volume of sound, the scope results of each input channel are as follows: