Testing code for master/tractor/server to interact with slave/remote control/client using a TTGO board and LoRa communication. This code runs on the server which is meant to be the laptop on the tractor.

ttgo_adafruit_server.ino

/* 
 * Program: ttgo_adafruit_server.ino
 * a simple messaging server(sender)with the RH_RF95 class.
*/


#include <SPI.h>
#include <RH_RF95.h>

//#define RFM95_CS  2    // "E"
//#define RFM95_RST 16   // "D"
//#define RFM95_INT 15   // "B"

// LoRa pins for TTGO Semtech SX1276 ref: https://microcontrollerslab.com/ttgo-lora32-sx1276-oled-board-pinout-getting-started-with-arduino-ide/
#define RFM95_MISO 19
#define RFM95_MOSI 27
#define RFM95_SCK 5
#define RFM95_CS 18    // #define RFM95_CS  2 
#define RFM95_INT 26   // #define RFM95_INT 15
#define RFM95_RST 14   // #define RFM95_RST 16 

#define LORA_BAND 915E6  //433E6 Asia; 866E6 Europe; 915E6 North America
//#define LORA_TxPower 20 // defaults to 17; 20 is highest
#define LORA_TxPower 5 // defaults to 17; 20 is highest
#define LORA_SyncWord 0xF1  // changes the sync word to match the receiver; ranges from 0-0xFF, default 0x34

// Change to 434.0 or other frequency, must match RX's freq!
#define RF95_FREQ 915.0

// Singleton instance of the radio driver
RH_RF95 rf95(RFM95_CS, RFM95_INT);

// LoRaMessage = String(readingID) + "/" + String(TempF) + "&" + String(humidity) + "#" + String(pressure);
struct dataStruct{
  float pressure; 
  float humidity;
  float TempF;
  unsigned long counter;
  }myData;

byte tx_buf[sizeof(myData)] = {0};


#define LED 2     // On board LED to blink for feedback

void setup() 
{
  pinMode(RFM95_RST, OUTPUT);
  digitalWrite(RFM95_RST, HIGH);

  Serial.begin(115200);
  while (!Serial) {
    delay(1);
  }

  delay(100);

  Serial.println("Feather LoRa TX Test!");

  // manual reset
  digitalWrite(RFM95_RST, LOW);
  delay(10);
  digitalWrite(RFM95_RST, HIGH);
  delay(10);
  SPI.begin(RFM95_SCK, RFM95_MISO, RFM95_MOSI, RFM95_CS); //SPI LoRa pins 

  while (!rf95.init()) {
    Serial.println("LoRa radio init failed");
    Serial.println("Uncomment '#define SERIAL_DEBUG' in RH_RF95.cpp for detailed debug info");
    while (1);
  }
  Serial.println("LoRa radio init OK!");

  // Defaults after init are 434.0MHz, modulation GFSK_Rb250Fd250, +13dbM
  if (!rf95.setFrequency(RF95_FREQ)) {
    Serial.println("setFrequency failed");
    while (1);
  }
  Serial.print("Set Freq to: "); Serial.println(RF95_FREQ);
  
  // Defaults after init are 434.0MHz, 13dBm, Bw = 125 kHz, Cr = 4/5, Sf = 128chips/symbol, CRC on

  // The default transmitter power is 13dBm, using PA_BOOST.
  // If you are using RFM95/96/97/98 modules which uses the PA_BOOST transmitter pin, then 
  // you can set transmitter powers from 5 to 23 dBm:
  rf95.setTxPower(5, false);
}

int16_t packetnum = 0;  // packet counter, we increment per xmission

void loop()
{
  delay(1000); // Wait 1 second between transmits, could also 'sleep' here!
  Serial.println("Transmitting..."); // Send a message to rf95_server
  
  char radiopacket[20] = "from tractor       ";
  // itoa(-1567, str, 10) should return string "-1567"
  itoa(packetnum++, radiopacket+13, 10);
  Serial.print("Sending "); Serial.println(radiopacket);
  radiopacket[19] = 0;
  
  Serial.println("Sending...");
  delay(10);
  rf95.send((uint8_t *)radiopacket, 20);

  Serial.println("Waiting for packet to complete..."); 
  delay(10);
  rf95.waitPacketSent();
  // Now wait for a reply
  uint8_t buf[RH_RF95_MAX_MESSAGE_LEN];
  uint8_t len = sizeof(buf);

  Serial.println("Waiting for reply...");
  if (rf95.waitAvailableTimeout(1000))
  { 
    // Should be a reply message for us now   
    if (rf95.recv(buf, &len))
   {
      Serial.print("Got reply: ");
      Serial.println((char*)buf);
      Serial.print("RSSI: ");
      Serial.println(rf95.lastRssi(), DEC);    
    }
    else
    {
      Serial.println("Receive failed");
    }
  }
  else
  {
    Serial.println("No messages being received");
  }

}