Samplerates of multiple audio inputs of the Audio Expander

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:

giuliomoro

ok thanks, now concentrate on j10 and j11. Connect pin 7 on j11 to pin 0 on j10, then you should be able to plug sound into input 7 and it should show up on input 0. Does that come in at full amplitude?

Bethanychm

giuliomoro I don't know if I understand you correctly. I plug the mic to pin7 of the caplet (J11-pin0 and J10-pin7 are suspended), and use ananlog(context, n/gAudioFramesPerAnalogFrame,0) to read the sound.

the render() code is:

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);  
	  }
    	scope.log(input);

  }
  
}

There is no change:

Is there something wrong with my understanding?

giuliomoro

ok that's interesting, can you remove the capelet and show on the scope:

what you get when plugging 3.3V into analog inputs 0, 1 and 2
what you get when plugging the signal from the microphone into analog input 0, 1 and 2

Make sure you only look at the analog input channel that you are plugging a signal into and not the unconnected ones

Bethanychm

giuliomoro

I plug 3.3V into analog inputs 0, 1 and 2:

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

  for(unsigned int n = 0; n < context->audioFrames; ++n)
  {
	  if((n%gAudioFramesPerAnalogFrame) == 0){
	    	input = analogRead(context, n/gAudioFramesPerAnalogFrame, 0);  % analog input channel from IN 0-2
	  }
    	scope.log(input);

  }
  
}

I plug the signal from the microphone into analog input 0, 1 and 2:

Is there something wrong with my understanding?

giuliomoro

That looks good: the bela cape is working as expected.

Now can you put the capelet back on, remove all the jumpers from it and do the same thing you just did, just plugging the microphones straight into the J10 pins?

Bethanychm

giuliomoro I do the same thing of step2:

Should I try the 3.3V?

giuliomoro

yes

Bethanychm

giuliomoro It looks so wired, so as IN2. Is this the contact issue of caplete and cape?