Code 10 sending data to TTN

// sending data to TTN

/*
 * HC-SR04 ultrasonic
 * +
 * DS18B20 temp sensor
 * +
 * Median
 * +
 * TTN (LoRaWAN)
*/
// librairies declaration
#include <OneWire.h> // to communicate with the temperature sensor
#include <DallasTemperature.h> // to command the temperature sensor
#include <RunningMedian.h> // to calculate mediants, from https://github.com/RobTillaart/Arduino/tree/master/libraries/RunningMedian
#include <MKRWAN_v2.h> // to control the LoRaWAN Modem (execute first the MKRWANFWUpdate_standalone)

LoRaModem modem; // declare the LoRaWAN modem

// variables declaration
String codeversion="1.10";
double ustime; //variable used to measure the US time [µs]
float usdist; // variable used to measure the distance [m]
float temp; // variable used to measure the temperature [°C]
unsigned int nsamples=20; // number of samples [-]
String appEui="0000000000000001";                 // from the TTN application (end device) - unique id of the end device
String appKey="CAE50CD13C2D33D16E97873F5C74FD7B"; // from the TTN application (end device) - application key for encryption
int counter=0; // counter to check that we are not missing messages

// Pins wiring (hardware)
const int TrigPin = 3; // pin to trigger a measure from the ultrasonic sensor
const int EchoPin = 4; // pin to measure the duration of the sound wave
#define ONE_WIRE_BUS 6 // Data wire is conntec to the Arduino digital pin 6
OneWire oneWire(ONE_WIRE_BUS); // Setup a oneWire instance to communicate with any OneWire devices
DallasTemperature DS18B20(&oneWire); // Pass our oneWire reference to Dallas Temperature sensor 

///////////////////////////////////////////////////
void setup() //SETUP - EXECUTE ONLY ONCE AT THE START
{   
  Serial.begin(9600); // initial serial connection
  pinMode(TrigPin, OUTPUT); // Set up the pin to start a new ultrasonic measure
  pinMode(EchoPin, INPUT);  // Set up pin to input mode to detect the ultrasonic wave 
  DS18B20.begin(); // Start up the temperature sensor library
  delay(2000); // sometimes it's good to wait a little
  Serial.println("version: "+codeversion); // write the version in the serial
  if (!modem.begin(EU868)) { // starts the LoRaWAN modem
    Serial.println("Failed to start module"); // if the modem doesn't start, stop the program
    while (1) {}
  };
  Serial.print("Your module version is: "); // some information regarding the LoRaWAN modem
  Serial.println(modem.version());
  Serial.print("Your device EUI is: ");
  Serial.println(modem.deviceEUI());

  int connected;
  appKey.trim(); // remove any unwanted space
  appEui.trim(); // remove any unwanted space
  connected = modem.joinOTAA(appEui, appKey); // OTAA connection (join) - Over-the-Air Activation = most secured communication
  if (!connected) { // check that the modem is connected to the network
    Serial.println("Something went wrong; are you indoor? Move near a window and retry");
    while (1) {}
  }
} 

//////////////////////////////////////////
void loop() // MAIN PROGRAM LOOP - FOREVER
{ 
  // Measurements
  temp=single_measure_TEMP(); //DS18B20 measure
  ustime = advanced_measure(); //ultrasonic measure - duration of signal in µs
  usdist = time_to_dist(ustime, temp); // convert duration into distance (with / without taking in account the air temperature)

  // Display values
  Serial.print("Ultrasonic time = ");
  Serial.print(ustime,0); // duration without decimals
  Serial.print(" µs and distance = ");
  Serial.print(usdist,3); // distance in m with 3 decimals (up to the millimeter)
  Serial.print(" m and temperature = ");
  Serial.print(temp, 2); // temperature in °C with 2 decimals
  Serial.println("°C");

  senddata(); // send the data using the LoRaWAN network (TTN = The Things Network)
  delay(30000); // wait 30 seconds for the next measurement
}

///////////////////////////////////////////////////////////////////////////
double single_measure_US() { // SUBROUTINE TO DO ONE ULTRASONIC MEASUREMENT
  double dtime; // variable use to store the duration of the pulse (for the measure of the distance)
  digitalWrite(TrigPin, LOW); 
  delayMicroseconds(10); // To be sure that the pin is low (0 V)
  digitalWrite(TrigPin, HIGH); 
  delayMicroseconds(10); // Generate a 10us high wave to trigger TrigPin (3.3 V)
  digitalWrite(TrigPin, LOW); 
  dtime = pulseIn(EchoPin, HIGH); // measure the duration in microseconds, https://www.arduino.cc/reference/en/language/functions/advanced-io/pulsein/
  delay(50); //pause (50ms) to make sure there is no interferences with the next measure
  return dtime; // send back the value from the subroutine to the main program (loop), time is in µs
}

/////////////////////////////////////////////////////////////////////////////////////////////
double advanced_measure() { // SUBROUTINE TO CONVERT SEVERAL RAW MEASUREMENT INTO ONE MEASURE
  double value;
  RunningMedian samples = RunningMedian(nsamples);
  Serial.print("  " + String(nsamples) + " samples: ");
  for(int i= 0; i<nsamples; i++){
    value = single_measure_US();   //US sensor measure
    if (value !=0) { //add only value different from zero
      Serial.print(value,0);
      Serial.print(", ");
      samples.add(value);
    }
  }
  double finalvalue=samples.getMedian(); //Return the median value
  Serial.print(" --> ");
  Serial.println(finalvalue, 0);
  return finalvalue; // send back the value from the subroutine to the main program (loop), consolided measure
}

//////////////////////////////////////////////////
float time_to_dist(double dtime, float temperat) {
  float distance =0; // distance in meters
  if (temperat = 0) {
    distance = dtime/2*343/1E6;
  } else {
    int RH = 50; // median relative humidity
    distance = dtime/2*(331.4+0.6*temperat+0.0124*RH)/1E6; //simplify formula
  }
  return distance;
}

/////////////////////////////
float single_measure_TEMP() {
  float tempDS18B20; // variable use to store the temperature
  DS18B20.requestTemperatures(); // Call sensors.requestTemperatures() to issue a global temperature and Requests to all devices on the bus
  tempDS18B20=DS18B20.getTempCByIndex(0);  // Why "byIndex"? You can have more than one IC on the same bus. 0 refers to the first IC on the wire (address)
  return tempDS18B20; // temperature in °C
}

/////////////////
void senddata() {
  // Data conversion (int)
  int temperat = temp*1000;
  int distance=usdist*1000;
  unsigned int duration = ustime;
  
   //  Prepare the data to be sent
  int err;
  byte payload[8];
  payload[0] = counter; // counter
  payload[1] = temperat/256; // multiple by 1000 to have a two-digit precision
  payload[2] = temperat%256; // multiple by 1000 to have a two-digit precision
  payload[3] = distance/256; // value already in mm
  payload[4] = distance%256; // value already in mm
  payload[5] = duration/(256*256);
  payload[6] = duration/256;
  payload[7] = duration%256;
  
  // Send the data
  modem.setPort(3);
  modem.beginPacket();
  modem.write(payload, sizeof(payload));   
  modem.endPacket(false);

  Serial.println("Message #"+String(counter)+ " sent with temp="+String(temp)+", duration="+String(ustime)+", distance="+String(usdist,3)+".");

  if (counter<255) {counter++;}
  else {counter=0;}
}

/*¨PAYLOAD FORMATER
 *
function decodeUplink(input) {
  var cou=input.bytes[0];
  var temp=(input.bytes[1]*256 + input.bytes[2])/1000;
  var dist=input.bytes[3]*256 + input.bytes[4];
  var dur=input.bytes[5]*256*256 + input.bytes[6]*256 + input.bytes[7];
  return {
    data: {
        counter: cou, termperature: temp, duration: dur, distance: dist, version:1 
    }
  };
}
 */