This was used to confirm the size of the structure and test using the memcpy function to copy from a structure to a buffer and then back again. This helped me clarify this concept would work in anticipation of including it in a LoRa radio master/slave setup.

structure_memcpy_test.ino

/*
 * This was used to confirm the size of the structure and test using the memcpy function to copy from a structure to a buffer and then back again.
 * This helped me clarify this concept would work in anticipation of including it in a lora radio master/slave setup.
 */
struct RadioControlStruct{
  int steering_val;
  int throttle_val;
  float press_norm ; 
  float press_hg;
  float temp;
  unsigned long counter;
  }RadioControlData;

struct RadioControlStruct2{
  int steering_val;
  int throttle_val;
  float press_norm ; 
  float press_hg;
  float temp;
  unsigned long counter;
  }RadioControlData2;

uint8_t RadioControlData_message_len = sizeof(RadioControlData);
uint8_t tx_RadioControlData_buf[sizeof(RadioControlData)] = {0};


struct TractorDataStruct{
  float heading_val;
  int speed_val;
  unsigned long counter;
  }TractorData;
byte tx_TractorData_buf[sizeof(TractorData)] = {0};
void setup() {
  // put your setup code here, to run once:
  startSerial();
  Serial.println("sizeof(RadioControlData): "); Serial.println(sizeof(RadioControlData));
  Serial.println("sizeof(TractorData): "); Serial.println(sizeof(TractorData));
  RadioControlData.steering_val = 255;
  RadioControlData.throttle_val = 4096;
  RadioControlData.press_norm=1000.11; 
  RadioControlData.press_hg=0.59; 
  RadioControlData.temp=22.394;
  RadioControlData.counter=65000;
  Serial.println("sizeof(RadioControlData): "); Serial.println(sizeof(RadioControlData));
  Serial.println("sizeof(TractorData): "); Serial.println(sizeof(TractorData));
  memcpy(tx_RadioControlData_buf, &RadioControlData, RadioControlData_message_len);
  // at this point you would transmit tx_RadioControlData_buf via lora radio
  
  tx_RadioControlData_buf[sizeof(RadioControlData)] = {0};  // to demonstrate the array is cleared out

  // then you would receive the transmission in a buffer and have to load the structure
  memcpy(&RadioControlData2, tx_RadioControlData_buf, RadioControlData_message_len);
  Serial.print("RadioControlData2.steering_val: "); Serial.println(RadioControlData2.steering_val);
  Serial.print("RadioControlData2.throttle_val: "); Serial.println(RadioControlData2.throttle_val);
  Serial.print("RadioControlData2.press_norm: "); Serial.println(RadioControlData2.press_norm);
  Serial.print("RadioControlData2.press_hg: "); Serial.println(RadioControlData2.press_hg);
  Serial.print("RadioControlData2.temp: "); Serial.println(RadioControlData2.temp);
  Serial.print("RadioControlData2.counter: "); Serial.println(RadioControlData2.counter);
}

void loop() {
  // put your main code here, to run repeatedly:

}
void startSerial(){
  Serial.begin(115200);
  while (!Serial) {
      delay(1000);   // loop forever and don't continue
  }
  Serial.println("starting: structure_size");
}