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Thread: Using the post processor functions for the audio output USB

  1. #1
    Junior Member
    Join Date
    Apr 2022
    Posts
    1

    Using the post processor functions for the audio output USB

    I am using the Teensy 3.2 and the audio adaptor board. I wanted to know if the Post Processor functions of the SGTL500 affect the USB audio output because I record the data in my computer from the USB and from the headphone output and the filters didn't seem to do something to the usb output. That's why I wanted to know if I need to add something else to my code or what can I do to get the filtlers work via the USB output. Also I wanted to know if there are functions like muteHeadphone() for the USB.

    My code of implementation is the following:
    Code:
    #include <Audio.h>
    #include <Wire.h>
    #include <SPI.h>
    #include <SD.h>
    #include <SerialFlash.h>
    
    AudioInputI2S            audioInput;           //xy=200,69
    AudioOutputI2S           audioOutput;           //xy=365,94
    AudioOutputUSB           usb1;
    //Connection to headphone output
    AudioConnection          patchCord1(audioInput, 0, audioOutput, 0);
    AudioConnection          patchCord2(audioInput, 0, audioOutput, 1);
    //Connection to usb output
    AudioConnection          patchCord3(audioInput, 0, usb1, 0);
    AudioConnection          patchCord4(audioInput, 0, usb1, 1);
    //Controller definition
    AudioControlSGTL5000     sgtl5000_1;     //xy=302,184
    
    const uint32_t Q_UNIT = 524288;
    const int F_S = 44100;
    const int myInput = AUDIO_INPUT_LINEIN;
    float vol = 0.5;
    int filterParams[5];
    
    void setup() {
      // Audio connections require memory to work.  For more
      // detailed information, see the MemoryAndCpuUsage example
      AudioMemory(12);
      Serial.begin(115200);
      // Enable the audio shield, select input, and enable output
      sgtl5000_1.enable();
      sgtl5000_1.inputSelect(myInput);
      sgtl5000_1.eqSelect(1);
      sgtl5000_1.audioPostProcessorEnable();
      sgtl5000_1.eqFilterCount(7);
      //sgtl5000_1.autoVolumeControl(2, 1, 0, -5, 0.5, 0.5);
    }
    
    void flat() {
      sgtl5000_1.enhanceBassDisable();
    }
    
    void setFilter(int f_number, int type, float f_c, float dbGain, float Q) {
      calcBiquad(type, f_c, dbGain, Q, Q_UNIT, F_S, filterParams);
      sgtl5000_1.eqFilter(f_number, filterParams);
    }
    
    void loop() {
      sgtl5000_1.volume(vol);
      
      if (Serial.available() > 0) {
        String data = Serial.readStringUntil('\n');
    
        if (data == "filt1") {
          Serial.println("FILTER 1");
          myInput = AUDIO_INPUT_LINEIN;
          //Select Filter Number: (0 - 6)
          int filter_num = 0;
          int filter1 = filter_num;
          //filter type: (0 -- Low Pass, 1 -- High Pass, 2--Bandpass, 3 -- Notch, 4 -- Parametric, 5--Low Shelf, 6 -- High Shelf);
          int type = 2;
          //filter variables
          float freq = 110;
          float dbGain = 5;
          float Q = 0.351;
          setFilter(filter1, type, freq, dbGain, Q);
        }
        else if (data == "filt2") {
          Serial.println("FILTER 2");
          //Select Filter Number: (0 - 6)
          int filter_num = 0;
          int filter1 = filter_num;
          //filter type: (0 -- Low Pass, 1 -- High Pass, 2--Bandpass, 3 -- Notch, 4 -- Parametric, 5--Low Shelf, 6 -- High Shelf);
          int type = 2;
          //filter variables
          float freq = 300;
          float dbGain = 5;
          float Q = 0.559;
          setFilter(filter1, type, freq, dbGain, Q);
        }
        else if (data == 'P') {
          vol = 0.5;
          
          Serial.println("Select from presets(0 -- Rock, 1 -- Classical)");
          while (!Serial.available()) {}
          char choice = Serial.read();
          int var = (int)choice - 48;
          switch (var) {
            case 0:
              Serial.println("Rock Equalizer");
              setFilter(0, FILTER_HIPASS, 90, 2.0, 1.0);
              setFilter(1, FILTER_PARAEQ, 155, 2.5, 2.0);
              setFilter(2, FILTER_PARAEQ, 600, 5.0, 0.2);
              setFilter(3, FILTER_PARAEQ, 1000, 4.0, 0.5);
              setFilter(4, FILTER_PARAEQ, 4000, 4.6, 0.8);
              setFilter(5, FILTER_NOTCH, 7000, 4.5, 0.4);
              setFilter(6, FILTER_HISHELF, 10000, 4.0, 16.0);
              sgtl5000_1.eqFilterCount(7);
              break;
            case 1:
              Serial.println("Classical Equalizer");
              setFilter(0, FILTER_HIPASS, 80, 4.0, 1.0);
              setFilter(1, FILTER_PARAEQ, 120, 2.0, 1.0);
              setFilter(2, FILTER_NOTCH, 3600, 2.5, 0.2);
              setFilter(3, FILTER_PARAEQ, 3000, 7.4, 0.2);
              setFilter(4, FILTER_PARAEQ, 80, 0, 1.0);
              setFilter(5, FILTER_PARAEQ, 500, 0, 1.0);
              setFilter(6, FILTER_PARAEQ, 9000, 2.2, 9.0);
              sgtl5000_1.eqFilterCount(7);
    
              break;
            default:
              Serial.println("Invalid Selection");
              break;
          }
        }
        else {
          Serial.println("Comando inválido");
        }
      }
    }
    Thank you for your help

  2. #2
    Senior Member
    Join Date
    Apr 2020
    Location
    Tucson
    Posts
    160
    The filters in the SGTL5000 are only going to affect the audio coming from the chip. I suggest adding a filter in your audio chain and using that instead. One filter gives you up to four passband functions.

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