void do_i2c_scanning() {
  if (i2c_scanning) {
    i2c_scanning = false;
    String tmp = i2c_scan();
    if (tmp == "error") {
      tmp = i2c_scan();
      Serial.println(tmp);
      jsonWriteStr(configLiveJson, "i2c", tmp);
    } else {
      Serial.println(tmp);
      jsonWriteStr(configLiveJson, "i2c", tmp);
    }
  }
}

String i2c_scan() {
  String out;
  byte count = 0;
  Wire.begin();
  for (byte i = 8; i < 120; i++) {
    Wire.beginTransmission(i);
    if (Wire.endTransmission() == 0) {
      count++;
      out += String(count) + ". 0x" + String(i, HEX) + "; ";
      delay(1);
    }
  }
  if (count == 0) {
    return "error";
  } else {
    return out;
  }
}