Are pin A16 and A17 suitable ADC with fft

StephanP · Jul 3, 2019

Hi,

At the moment I am trying to get an analog mic to connect to a Teensy 3.5. I'd like to use pin A16 or A17 because these are free on the PCB where the teensy is plugged in to.
For the mic I use a MAX9812 amp in between which so most of the sound will be on a voltage level between 0 and 1.2v.

The code I am using is working an a Teensy 3.2 on pin A3 but also not in pin A17.

So the main question is, is it possible to attach a mic to A16 or A17 to perform fft?

This is the code I'm using:

Code:

#include <Audio.h>
#include <Wire.h>
#include <SPI.h>
#include <SD.h>
#include <SerialFlash.h>


#define MIC_ANALOG A17

#define MIC_GAIN  10  // multiplier for the specific mic
// GUItool: begin automatically generated code

// Actions
AudioAnalyzePeak         peak1;          //xy=495,162
AudioAnalyzeFFT256       fft256_1;       //xy=496,230
AudioAnalyzeRMS          rms1;           //xy=505,109

// Analog mic
AudioInputAnalog         adc1(MIC_ANALOG);       //default for adc1 is A2       3.3v
AudioConnection          patchCord1(adc1, fft256_1);
AudioConnection          patchCord2(adc1, rms1);
AudioConnection          patchCord3(adc1, peak1);

// An array to hold the 16 frequency bands
long output_interval = 2000;
float fft_level[16];
int loopcounter =0;
float rms =0;
float peak = 0;
long mill_counter;

// frequency bin spreading
int fft_bin[17] = {2,3,4,6,8,10,13,16,20,24,29,34,40,47,54,62,70};

const String sensDivider = ", ";





//*********************************************************************************** SETUP
void setup()
{

  // Audio connections require memory to work.
  AudioMemory(12);

  // Configure the window algorithm to use
  fft256_1.windowFunction(AudioWindowHanning256);
  fft256_1.averageTogether(255);
}

//*********************************************************************************** FFT256

void read_fft256()
{
  if (fft256_1.available())
  {
    // each time new FFT data is available, fft_bin it into 16 channels
    // Note- response doesn't seem flat so each is normalized <experimenting!
    // Note- these calculations go very fast!!

    // Band are 172Hz wide

    fft_level[0] +=  fft256_1.read(fft_bin[0],fft_bin[1]-1) * 1 * MIC_GAIN;
    fft_level[1] +=  fft256_1.read(fft_bin[1],fft_bin[2]-1) * 1 * MIC_GAIN;
    fft_level[2] +=  fft256_1.read(fft_bin[2],fft_bin[3]-1) * 1 * MIC_GAIN;
    fft_level[3] +=  fft256_1.read(fft_bin[3],fft_bin[4]-1) * 1 * MIC_GAIN;
    fft_level[4] +=  fft256_1.read(fft_bin[4],fft_bin[5]-1) * 1 * MIC_GAIN;
    fft_level[5] +=  fft256_1.read(fft_bin[5],fft_bin[6]-1) * 1 * MIC_GAIN;
    fft_level[6] +=  fft256_1.read(fft_bin[6],fft_bin[7]-1) * 1 * MIC_GAIN;
    fft_level[7] +=  fft256_1.read(fft_bin[7],fft_bin[8]-1) * 1 * MIC_GAIN;
    fft_level[8] +=  fft256_1.read(fft_bin[8],fft_bin[9]-1) * 1 * MIC_GAIN;
    fft_level[9] +=  fft256_1.read(fft_bin[9],fft_bin[10]-1) * 1 * MIC_GAIN;
    fft_level[10] += fft256_1.read(fft_bin[10],fft_bin[11]-1) * 1 * MIC_GAIN;
    fft_level[11] += fft256_1.read(fft_bin[11],fft_bin[12]-1) * 1 * MIC_GAIN;
    fft_level[12] += fft256_1.read(fft_bin[12],fft_bin[13]-1) * 1 * MIC_GAIN;
    fft_level[13] += fft256_1.read(fft_bin[13],fft_bin[14]-1) * 1 * MIC_GAIN;
    fft_level[14] += fft256_1.read(fft_bin[14],fft_bin[15]-1) * 1 * MIC_GAIN;
    fft_level[15] += fft256_1.read(fft_bin[15],fft_bin[16]-1) * 1 * MIC_GAIN;
    loopcounter += 1;
  }
  // else
  // {
  //   Serial.println("FFT not available");
  // }
}

//*********************************************************************************** Counter

bool output_audio()
{
  if (millis() > mill_counter + output_interval)
  {
    Serial.print("fft_0=");  Serial.print(fft_level[0]/loopcounter);     Serial.print(sensDivider);
    Serial.print("fft_1=");     Serial.print(fft_level[1]/loopcounter);     Serial.print(sensDivider);
    Serial.print("fft_2=");     Serial.print(fft_level[2]/loopcounter);     Serial.print(sensDivider);
    Serial.print("fft_3=");     Serial.print(fft_level[3]/loopcounter);     Serial.print(sensDivider);
    Serial.print("fft_4=");     Serial.print(fft_level[4]/loopcounter);     Serial.print(sensDivider);
    Serial.print("fft_5=");     Serial.print(fft_level[5]/loopcounter);     Serial.print(sensDivider);
    Serial.print("fft_6=");     Serial.print(fft_level[6]/loopcounter);     Serial.print(sensDivider);
    Serial.print("fft_7=");     Serial.print(fft_level[7]/loopcounter);     Serial.print(sensDivider);
    Serial.print("fft_8=");     Serial.print(fft_level[8]/loopcounter);     Serial.print(sensDivider);
    Serial.print("fft_9=");     Serial.print(fft_level[9]/loopcounter);     Serial.print(sensDivider);
    Serial.print("fft_10=");    Serial.print(fft_level[10]/loopcounter);    Serial.print(sensDivider);
    Serial.print("fft_11=");    Serial.print(fft_level[11]/loopcounter);    Serial.print(sensDivider);
    Serial.print("fft_12=");    Serial.print(fft_level[12]/loopcounter);    Serial.print(sensDivider);
    Serial.print("fft_13=");    Serial.print(fft_level[13]/loopcounter);    Serial.print(sensDivider);
    Serial.print("fft_14=");    Serial.print(fft_level[14]/loopcounter);    Serial.print(sensDivider);
    Serial.print("fft_15=");    Serial.print(fft_level[15]/loopcounter);    Serial.print(sensDivider);
    Serial.print("RMS=");       Serial.print(rms/loopcounter);  Serial.print(sensDivider);
    Serial.print("Peak=");      Serial.print (peak1.readPeakToPeak()); Serial.print(sensDivider);
    Serial.print("Loopcounter=");Serial.println(loopcounter);

    for (size_t i = 0; i < 16; i++)
      {
          fft_level[i]=0;
      }

    mill_counter=millis();
    loopcounter=0;
    rms =0;
    return true;
  }
}

//*********************************************************************************** RMS

void read_rms()
{
  if (rms1.available())
  {
    rms += rms1.read();
  }
}

//*********************************************************************************** LOOP
void loop()
{
read_fft256();
read_rms();
output_audio();
}

Who can help me figuring out if this is possible or what I am doing wrong

manitou · Jul 3, 2019

A little above my pay grade, but audio lib wants to have an ADC pin on ADC0 and the other on ADC1 (A2 and A3 can satisfy that, but i don't think A16 and A17 are on distinct ADC controllers) See https://forum.pjrc.com/threads/25532-ADC-library-update-now-with-support-for-Teensy-3-1 for ADC pin mappings to ADC controller, also i assume T3.5 reference manual also shows ADC pin mappings.

https://github.com/PaulStoffregen/Audio/blob/master/input_adcs.cpp

StephanP · Jul 8, 2019

Thanks for the explanation!
When I read the tread you talk about (https://forum.pjrc.com/threads/25532-ADC-library-update-now-with-support-for-Teensy-3-1) I read the I I can use any Analog pin with ADC. On the pin I'd like to use A17 I can only use ADC1 which I use in the code.

Is there something I do miss?

manitou · Jul 8, 2019

My first reply was faulty, I thought you were trying to use AudioInputAnalogStereo() with two pins -- which required one pin on ADC0 and the other on ADC1. Your question was about just one pin AudioInputAnalog(). If you look at the lib's input_adc.cpp, you will see that it is hardwired to use only ADC0, so neither A16 nor A17 will work. From the T3.5 images at https://forum.pjrc.com/threads/25532-ADC-library-update-now-with-support-for-Teensy-3-1, you can see that ADC0 pins include A0-A11, A14, A15, and A21.

View attachment 11814

StephanP · Jul 11, 2019

Ah thats the cause! So only ADC1 can do AudioInputAnalog.
Thanks for the quick and clear explenation!

Are pin A16 and A17 suitable ADC with fft

StephanP

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manitou

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StephanP

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manitou

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StephanP

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