Teensy 4.1 with Audio Adaptor only noise when recoding but playback is working


Im want to record some audio with the teensy 4.1. But I am unable. I only get noise, regardless of what I am trying. But playback is no problem. But I have to use ti SD Card on the teensy otherwise there is extreme noise.
I have just adjusted the example code to use the other SD Card.
I have tried using “Lin In” and “Mic In” in the software aswell as different gains. I plug in the microphone via the 3,5mm audio jack. I have tried normal headphones with a mic (Bose SoundSport Wired) aswell as a lavalier mic.
This is my code (recoder axample with some adjustments (pins)):
// Record sound as raw data to a SD card, and play it back.
// Requires the audio shield:
//   http://www.pjrc.com/store/teensy3_audio.html
// Three pushbuttons need to be connected:
//   Record Button: pin 33 to GND
//   Stop Button:   pin 34 to GND
//   Play Button:   pin 35 to GND
// This example code is in the public domain.

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

// GUItool: begin automatically generated code
AudioInputI2S            i2s2;           //xy=105,63
AudioAnalyzePeak         peak1;          //xy=278,108
AudioRecordQueue         queue1;         //xy=281,63
AudioPlaySdRaw           playRaw1;       //xy=302,157
AudioOutputI2S           i2s1;           //xy=470,120
AudioConnection          patchCord1(i2s2, 0, queue1, 0);
AudioConnection          patchCord2(i2s2, 0, peak1, 0);
AudioConnection          patchCord3(playRaw1, 0, i2s1, 0);
AudioConnection          patchCord4(playRaw1, 0, i2s1, 1);
AudioControlSGTL5000     sgtl5000_1;     //xy=265,212
// GUItool: end automatically generated code

// For a stereo recording version, see this forum thread:
// https://forum.pjrc.com/threads/46150?p=158388&viewfull=1#post158388

// A much more advanced sound recording and data logging project:
// https://github.com/WMXZ-EU/microSoundRecorder
// https://github.com/WMXZ-EU/microSoundRecorder/wiki/Hardware-setup
// https://forum.pjrc.com/threads/52175?p=185386&viewfull=1#post185386

// Bounce objects to easily and reliably read the buttons
Bounce buttonRecord = Bounce(33, 8);
Bounce buttonStop =   Bounce(34, 8);  // 8 = 8 ms debounce time
Bounce buttonPlay =   Bounce(35, 8);

// which input on the audio shield will be used?
const int myInput = AUDIO_INPUT_LINEIN;
//const int myInput = AUDIO_INPUT_MIC;

// Use these with the Teensy Audio Shield
//#define SDCARD_CS_PIN    10
#define SDCARD_MOSI_PIN  11   // Teensy 4 ignores this, uses pin 11
#define SDCARD_SCK_PIN   13  // Teensy 4 ignores this, uses pin 13

// Use these with the Teensy 3.5 & 3.6 & 4.1 SD card
//#define SDCARD_MOSI_PIN  11  // not actually used
//#define SDCARD_SCK_PIN   13  // not actually used

// Use these for the SD+Wiz820 or other adaptors
//#define SDCARD_CS_PIN    4
//#define SDCARD_MOSI_PIN  11
//#define SDCARD_SCK_PIN   13

// Remember which mode we're doing
int mode = 0;  // 0=stopped, 1=recording, 2=playing

// The file where data is recorded
File frec;

void setup() {
  // Configure the pushbutton pins
  pinMode(33, INPUT_PULLUP);
  pinMode(34, INPUT_PULLUP);
  pinMode(35, INPUT_PULLUP);

  // Audio connections require memory, and the record queue
  // uses this memory to buffer incoming audio.

  // Enable the audio shield, select input, and enable output

  // Initialize the SD card
  if (!(SD.begin(SDCARD_CS_PIN))) {
    // stop here if no SD card, but print a message
    while (1) {
      Serial.println("Unable to access the SD card");

void loop() {
  // First, read the buttons

  // Respond to button presses
  if (buttonRecord.fallingEdge()) {
    Serial.println("Record Button Press");
    if (mode == 2) stopPlaying();
    if (mode == 0) startRecording();
  if (buttonStop.fallingEdge()) {
    Serial.println("Stop Button Press");
    if (mode == 1) stopRecording();
    if (mode == 2) stopPlaying();
  if (buttonPlay.fallingEdge()) {
    Serial.println("Play Button Press");
    if (mode == 1) stopRecording();
    if (mode == 0) startPlaying();

  // If we're playing or recording, carry on...
  if (mode == 1) {
  if (mode == 2) {

  // when using a microphone, continuously adjust gain
  if (myInput == AUDIO_INPUT_MIC) adjustMicLevel();

void startRecording() {
  if (SD.exists("RECORD.RAW")) {
    // The SD library writes new data to the end of the
    // file, so to start a new recording, the old file
    // must be deleted before new data is written.
  frec = SD.open("RECORD.RAW", FILE_WRITE);
  if (frec) {
    mode = 1;

void continueRecording() {
  if (queue1.available() >= 2) {
    byte buffer[512];
    // Fetch 2 blocks from the audio library and copy
    // into a 512 byte buffer.  The Arduino SD library
    // is most efficient when full 512 byte sector size
    // writes are used.
    memcpy(buffer, queue1.readBuffer(), 256);
    memcpy(buffer+256, queue1.readBuffer(), 256);
    // write all 512 bytes to the SD card
    //elapsedMicros usec = 0;
    frec.write(buffer, 512);
    // Uncomment these lines to see how long SD writes
    // are taking.  A pair of audio blocks arrives every
    // 5802 microseconds, so hopefully most of the writes
    // take well under 5802 us.  Some will take more, as
    // the SD library also must write to the FAT tables
    // and the SD card controller manages media erase and
    // wear leveling.  The queue1 object can buffer
    // approximately 301700 us of audio, to allow time
    // for occasional high SD card latency, as long as
    // the average write time is under 5802 us.
    //Serial.print("SD write, us=");

void stopRecording() {
  if (mode == 1) {
    while (queue1.available() > 0) {
      frec.write((byte*)queue1.readBuffer(), 256);
  mode = 0;

void startPlaying() {
  mode = 2;

void continuePlaying() {
  if (!playRaw1.isPlaying()) {
    mode = 0;

void stopPlaying() {
  if (mode == 2) playRaw1.stop();
  mode = 0;

void adjustMicLevel() {
  // TODO: read the peak1 object and adjust sgtl5000_1.micGain()
  // if anyone gets this working, please submit a github pull request :-)

Has anyone an idea?


I think I have found a solution. I think it is not possible to record audio via the 3.5mm jack. I have tried it now via the MIX and GND Pins on the board and with that it works fine. Is there a way to record audio via the 3.5mm jack?

Its a TRS connector, not TRRS, so there's physically no connection to a mic - the schematic is available on the page about the audio adaptor.