How connect arduino mega on Serial3 like USB

  • Hello
    I need some help. Can someone tell me how to make connection on Serial3 in arduino mega?
    i use something like this:

    // Enable debug prints to serial monitor
    //#define MY_DEBUG
    #define MY_GATEWAY_SERIAL Serial3
    #define MY_SERIALDEVICE Serial3
    // Enable RS485 transport layer
    #define MY_RS485
    // Define this to enables DE-pin management on defined pin
    #define MY_RS485_DE_PIN 2
    // Set RS485 baud rate to use
    #define MY_RS485_BAUD_RATE 115200
    // Enable this if RS485 is connected to a hardware serial port
    #define MY_RS485_HWSERIAL Serial3
    #include <SPI.h>
    #include <MySensors.h>  
    #include <DallasTemperature.h>
    #include <OneWire.h>
    #define COMPARE_TEMP 1 // Send temperature only if changed? 1 = Yes 0 = No
    #define ONE_WIRE_BUS 7 // Pin where dallase sensor is connected 
    #define MAX_ATTACHED_DS18B20 16
    unsigned long SLEEP_TIME = 30000; // Sleep time between reads (in milliseconds)
    OneWire oneWire(ONE_WIRE_BUS); // Setup a oneWire instance to communicate with any OneWire devices (not just Maxim/Dallas temperature ICs)
    DallasTemperature sensors(&oneWire); // Pass the oneWire reference to Dallas Temperature. 
    float lastTemperature[MAX_ATTACHED_DS18B20];
    int numSensors=0;
    bool receivedConfig = false;
    bool metric = true;
    // Initialize temperature message
    MyMessage msg(0,V_TEMP);
    void before()
      // Startup up the OneWire library
    void setup()  
      // requestTemperatures() will not block current thread
    void presentation() {
      // Send the sketch version information to the gateway and Controller
      sendSketchInfo("Temperature Sensor", "1.1");
      // Fetch the number of attached temperature sensors  
      numSensors = sensors.getDeviceCount();
      // Present all sensors to controller
      for (int i=0; i<numSensors && i<MAX_ATTACHED_DS18B20; i++) {   
         present(i, S_TEMP);
    void loop()     
      // Fetch temperatures from Dallas sensors
      // query conversion time and sleep until conversion completed
      int16_t conversionTime = sensors.millisToWaitForConversion(sensors.getResolution());
      // sleep() call can be replaced by wait() call if node need to process incoming messages (or if node is repeater)
      // Read temperatures and send them to controller 
      for (int i=0; i<numSensors && i<MAX_ATTACHED_DS18B20; i++) {
        // Fetch and round temperature to one decimal
        float temperature = static_cast<float>(static_cast<int>((getControllerConfig().isMetric?sensors.getTempCByIndex(i):sensors.getTempFByIndex(i)) * 10.)) / 10.;
        // Only send data if temperature has changed and no error
        #if COMPARE_TEMP == 1
        if (lastTemperature[i] != temperature && temperature != -127.00 && temperature != 85.00) {
        if (temperature != -127.00 && temperature != 85.00) {
          // Send in the new temperature
          // Save new temperatures for next compare

    But on serial i get this:

    055;;01;aea tru opee02550;0;182.2.0;5;;;1;emeraue Snsr025530;1;.1

    Not good 😞