Send struct with string by LoRa (Arduino)

I'm trying to send some data with LoRa but I only receive single chars (line by line) or float, int, byte...

I want to send "msg" like a string.

I have:

struct DATA {
  char msg = "";
  int valor;
};
DATA MyData;
.
.
.
void loop() {
  if (Serial.available() > 0) {
    MyData.msg = Serial.read();
    MyData.valor = 10;
    Transceiver.SendStruct((uint8_t*) &MyData, (uint8_t) sizeof(MyData));
    Serial.print("Sending: "); Serial.println(MyData.msg); Serial.println(MyData.valor);
  }
}

it works but if I send: "hello world", I will receive:

h
10
e
10
l
10
.
.
.

So I tried to make an aux variable:

if (Serial.available() > 0) {
  char aux = Serial.read();
  MyData.msg += aux;
  MyData.valor = 10;
  Transceiver.SendStruct((uint8_t*) &MyData, (uint8_t) sizeof(MyData));
  Serial.print("Sending: "); Serial.println(MyData.msg); Serial.println(MyData.valor);
}

But I receive only unrecognized chars.

PS1: If I change struct char with a String, I receive only unrecognized chars.

PS2: I tried to make a "for" with the sizeof on receive to join the chars to make a string, but it doesn't work either.

Thanks in advance.

Solution

Your MyData.msg is defined as a char which is a single character instead of an array[]. You need to define your struct as:

#define MAX_STR_LENGTH 20

typedef struct {
  char msg[MAX_STR_LENGTH] = '\0';  // an array of char
  int valor = 0;
} Data_t;

Data_t Mydata;

You are sending the struct data each time a char is received instead of of waiting for the whole string is received. Assuming the string you received from Serial is terminated with \n. You can read in the whole string by checking with the received char is an \n and only send the struct then.

void loop() {
   static int i = 0;
   while (Serial.available() > 0) {
    char c = Serial.read();
    if (c != '\n') {
      MyData.msg[i] = c;
      i++;
    }
    else {
      // terminate the array with NULL terminator and send the struct
      MyData.msg[i] = '\0';
      MyData.valor = 10;
      Transceiver.SendStruct((uint8_t*) &MyData, (uint8_t) sizeof(MyData));
      Serial.print("Sending: "); 
      Serial.println(MyData.msg);
      Serial.println(MyData.valor);
      i = 0;
    }
  }
}