mit welcher I2C Adresse?
manche I2C libs verwenden übrigens die 7-bit Adresse (u.a. Arduino), manche die 8-bit Adresse.

für Arduino:

Code:
    // --------------------------------------
    // i2c_scanner
    //    
    // This sketch tests the standard 7-bit addresses
    // Devices with higher bit address might not be seen properly.
    //
     
    #include <Wire.h>
    
    #define ESP_SDA 4 //GPIO4=D2 SDA ESP8266 default
    #define ESP_SCL 5 //GPIO5=D1 SCL ESP8266 default

    byte error, address;
    int nDevices;
 
    void setup()
    {            
      // Wire.begin(ESP_SDA,ESP_SCL);  // only for ESP8266 if not default
      
      Wire.begin();                    // AVR, ARM, ESP8266 default
 
      Serial.begin(115200);
      while (!Serial);                 // Leonardo: wait for serial monitor

      Serial.println("\nI2C Scanner");     
      Serial.println("\nScanning...");           
    }
     
     
    void loop()
    {
      nDevices = 0;
      for(address = 0; address < 128; address++ )
      {

        if (address%16 == 0)  {   
          Serial.println();  
          Serial.print( (address+1)/16);
          Serial.print("  ");
        }

        
        if(address==0 || address==127) {
           Serial.print("** ");
           continue;
        }
        
        Wire.beginTransmission(address);
        error = Wire.endTransmission();
     
        if (error == 0)
        {          
          if (address<16) Serial.print("0"); 
          Serial.print(address,HEX); Serial.print(" ");         
          nDevices++;
        }
        else if (error==4)
        {
          Serial.print("?? ");   
        }    
        else
        {      
           Serial.print("-- ");   
        }          
      }
      
      Serial.println();
      Serial.print("found: "); Serial.print(nDevices); Serial.print(" devices \n");
      delay(10000);      
    }