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Thread: Going around in circles here... I2C working or not....

  1. #1
    Senior Member
    Join Date
    May 2015

    Going around in circles here... I2C working or not....

    Ok I can play the wave file in the tutorial also the one that just beeps works. Can anyone verify that means that the I2C bus MUST be working with the Teensy?

    I am not seeing the chip when I scan the buss but I don't understand how it could be playing a wave from a microSD without the I2C working.

    I only get to work on this for 1-2 hours a day whenever things are slow at work. Restarting like this I don't really make progress when I forget what I accomplished last week and haven't look at for over a week.

  2. #2
    Senior Member PaulStoffregen's Avatar
    Join Date
    Nov 2012
    Maybe you're using the audio shield?

    The SGTL5000 chip stays in a low power disabled state until it hears 8 clock pulses on MCLK. It won't reply to the Wire library Scanner example while in that low power state. It also can't reply unless a clock signal is present on that pin.

    If using Teensy 4.0 or 4.1 (also can't tell which Teensy model you have) MCLK is on pin 23. Here's a copy of the Scanner example with a couple lines added to send a 6 MHz PWM signal for MCLK.

    #include <Wire.h>
    void setup() {
      // uncomment these to use alternate pins
      while (!Serial);        // Leonardo: wait for serial monitor
      Serial.println(F("\nI2C Scanner"));
      analogWriteFrequency(23, 6000000);
      analogWrite(23, 128);   // simulate MCLK signal to SGTL5000
    void loop() {
      byte error, address;
      int nDevices;
      nDevices = 0;
      for (address = 1; address < 127; address++) {
        // The i2c_scanner uses the return value of
        // the Write.endTransmisstion to see if
        // a device did acknowledge to the address.
        error = Wire.endTransmission();
        if (error == 0) {
          Serial.print(F("Device found at address 0x"));
          if (address < 16) {
          Serial.print("  (");
        } else if (error==4) {
          Serial.print(F("Unknown error at address 0x"));
          if (address < 16) {
      if (nDevices == 0) {
        Serial.println(F("No I2C devices found\n"));
      } else {
      delay(5000);           // wait 5 seconds for next scan
    void printKnownChips(byte address)
      // Is this list missing part numbers for chips you use?
      // Please suggest additions here:
      switch (address) {
        case 0x00: Serial.print(F("AS3935")); break;
        case 0x01: Serial.print(F("AS3935")); break;
        case 0x02: Serial.print(F("AS3935")); break;
        case 0x03: Serial.print(F("AS3935")); break;
        case 0x04: Serial.print(F("ADAU1966")); break;
        case 0x0A: Serial.print(F("SGTL5000")); break; // MCLK required
        case 0x0B: Serial.print(F("SMBusBattery?")); break;
        case 0x0C: Serial.print(F("AK8963")); break;
        case 0x10: Serial.print(F("CS4272")); break;
        case 0x11: Serial.print(F("Si4713")); break;
        case 0x13: Serial.print(F("VCNL4000,AK4558")); break;
        case 0x18: Serial.print(F("LIS331DLH")); break;
        case 0x19: Serial.print(F("LSM303,LIS331DLH")); break;
        case 0x1A: Serial.print(F("WM8731")); break;
        case 0x1C: Serial.print(F("LIS3MDL")); break;
        case 0x1D: Serial.print(F("LSM303D,LSM9DS0,ADXL345,MMA7455L,LSM9DS1,LIS3DSH")); break;
        case 0x1E: Serial.print(F("LSM303D,HMC5883L,FXOS8700,LIS3DSH")); break;
        case 0x20: Serial.print(F("MCP23017,MCP23008,PCF8574,FXAS21002,SoilMoisture")); break;
        case 0x21: Serial.print(F("MCP23017,MCP23008,PCF8574")); break;
        case 0x22: Serial.print(F("MCP23017,MCP23008,PCF8574")); break;
        case 0x23: Serial.print(F("MCP23017,MCP23008,PCF8574")); break;
        case 0x24: Serial.print(F("MCP23017,MCP23008,PCF8574,ADAU1966,HM01B0")); break;
        case 0x25: Serial.print(F("MCP23017,MCP23008,PCF8574")); break;
        case 0x26: Serial.print(F("MCP23017,MCP23008,PCF8574")); break;
        case 0x27: Serial.print(F("MCP23017,MCP23008,PCF8574,LCD16x2,DigoleDisplay")); break;
        case 0x28: Serial.print(F("BNO055,EM7180,CAP1188")); break;
        case 0x29: Serial.print(F("TSL2561,VL6180,TSL2561,TSL2591,BNO055,CAP1188")); break;
        case 0x2A: Serial.print(F("SGTL5000,CAP1188")); break;
        case 0x2B: Serial.print(F("CAP1188")); break;
        case 0x2C: Serial.print(F("MCP44XX ePot")); break;
        case 0x2D: Serial.print(F("MCP44XX ePot")); break;
        case 0x2E: Serial.print(F("MCP44XX ePot")); break;
        case 0x2F: Serial.print(F("MCP44XX ePot")); break;
        case 0x30: Serial.print(F("Si7210")); break;
        case 0x31: Serial.print(F("Si7210")); break;
        case 0x32: Serial.print(F("Si7210")); break;
        case 0x33: Serial.print(F("MAX11614,MAX11615,Si7210")); break;
        case 0x34: Serial.print(F("MAX11612,MAX11613")); break;
        case 0x35: Serial.print(F("MAX11616,MAX11617")); break;
        case 0x38: Serial.print(F("RA8875,FT6206,MAX98390")); break;
        case 0x39: Serial.print(F("TSL2561, APDS9960")); break;
        case 0x3C: Serial.print(F("SSD1306,DigisparkOLED")); break;
        case 0x3D: Serial.print(F("SSD1306")); break;
        case 0x40: Serial.print(F("PCA9685,Si7021,MS8607")); break;
        case 0x41: Serial.print(F("STMPE610,PCA9685")); break;
        case 0x42: Serial.print(F("PCA9685")); break;
        case 0x43: Serial.print(F("PCA9685")); break;
        case 0x44: Serial.print(F("PCA9685, SHT3X, ADAU1966")); break;
        case 0x45: Serial.print(F("PCA9685, SHT3X")); break;
        case 0x46: Serial.print(F("PCA9685")); break;
        case 0x47: Serial.print(F("PCA9685")); break;
        case 0x48: Serial.print(F("ADS1115,PN532,TMP102,LM75,PCF8591,CS42448")); break;
        case 0x49: Serial.print(F("ADS1115,TSL2561,PCF8591,CS42448")); break;
        case 0x4A: Serial.print(F("ADS1115,Qwiic Keypad,CS42448")); break;
        case 0x4B: Serial.print(F("ADS1115,TMP102,BNO080,Qwiic Keypad,CS42448")); break;
        case 0x50: Serial.print(F("EEPROM,FRAM")); break;
        case 0x51: Serial.print(F("EEPROM")); break;
        case 0x52: Serial.print(F("Nunchuk,EEPROM")); break;
        case 0x53: Serial.print(F("ADXL345,EEPROM")); break;
        case 0x54: Serial.print(F("EEPROM")); break;
        case 0x55: Serial.print(F("EEPROM")); break;
        case 0x56: Serial.print(F("EEPROM")); break;
        case 0x57: Serial.print(F("EEPROM")); break;
        case 0x58: Serial.print(F("TPA2016,MAX21100")); break;
        case 0x5A: Serial.print(F("MPR121")); break;
        case 0x60: Serial.print(F("MPL3115,MCP4725,MCP4728,TEA5767,Si5351")); break;
        case 0x61: Serial.print(F("MCP4725,AtlasEzoDO")); break;
        case 0x62: Serial.print(F("LidarLite,MCP4725,AtlasEzoORP")); break;
        case 0x63: Serial.print(F("MCP4725,AtlasEzoPH")); break;
        case 0x64: Serial.print(F("AtlasEzoEC, ADAU1966")); break;
        case 0x66: Serial.print(F("AtlasEzoRTD")); break;
        case 0x68: Serial.print(F("DS1307,DS3231,MPU6050,MPU9050,MPU9250,ITG3200,ITG3701,LSM9DS0,L3G4200D")); break;
        case 0x69: Serial.print(F("MPU6050,MPU9050,MPU9250,ITG3701,L3G4200D")); break;
        case 0x6A: Serial.print(F("LSM9DS1")); break;
        case 0x6B: Serial.print(F("LSM9DS0")); break;
        case 0x6F: Serial.print(F("Qwiic Button")); break;
        case 0x70: Serial.print(F("HT16K33,TCA9548A")); break;
        case 0x71: Serial.print(F("SFE7SEG,HT16K33")); break;
        case 0x72: Serial.print(F("HT16K33")); break;
        case 0x73: Serial.print(F("HT16K33")); break;
        case 0x76: Serial.print(F("MS5607,MS5611,MS5637,BMP280")); break;
        case 0x77: Serial.print(F("BMP085,BMA180,BMP280,MS5611")); break;
        case 0x7C: Serial.print(F("FRAM_ID")); break;
        default: Serial.print(F("unknown chip"));

  3. #3
    Senior Member
    Join Date
    May 2015
    Awesome Paul Thank you thank you thank you. For the record I am using 3.2's and the proper shield.

    Nothing like shooting yourself in the foot over and over. You made my day. Somehow I had it show up using a scanner and then just stop later when I tried to run it again. I must have had moved in some of the Audio.h to a version that worked then moved back to the example. figured I blew up another audio sheild.

    I bet all 3 audio shields I have are actually good when I thought my custom board was blowing them up.

  4. #4
    Senior Member
    Join Date
    May 2015
    I see that MCLK is on 11 not 23 on the 3.2 so I will make that change tomorrow if things are slow enough so I get to work on it.

  5. #5
    Join Date
    Sep 2021
    You can also just add an audio I2S - this chooses the right pin automatically and provides the clock.

  6. #6
    Senior Member
    Join Date
    May 2015
    I thanks for the help guys

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