ESP32 LoRa Remote Sensor Node (Point-to-Point)

// ESP32 LoRa point-to-point DHT22 sender/receiver
// Select NODE_MODE_SENDER on one board and NODE_MODE_RECEIVER on the second board.
// Always connect the correct antenna before transmitting.
#include <SPI.h>
#include <LoRa.h>
#include <DHT.h>

#define NODE_MODE_SENDER 1

const long LORA_FREQUENCY_HZ = 915E6; // Change to a legal frequency for your region and module.
const int LORA_SCK = 18;
const int LORA_MISO = 19;
const int LORA_MOSI = 23;
const int LORA_CS = 5;
const int LORA_RST = 14;
const int LORA_DIO0 = 26;
const int DHT_PIN = 4;

DHT dht(DHT_PIN, DHT22);
uint32_t sequenceNumber = 0;
uint32_t badPackets = 0;

bool initLoRa() {
  SPI.begin(LORA_SCK, LORA_MISO, LORA_MOSI, LORA_CS);
  LoRa.setPins(LORA_CS, LORA_RST, LORA_DIO0);
  if (!LoRa.begin(LORA_FREQUENCY_HZ)) return false;
  LoRa.setTxPower(10); // Conservative starter value; obey local legal limits.
  return true;
}

bool parsePacket(String packet, int &node, float &tempC, float &humidity, uint32_t &seq) {
  packet.trim();
  int a = packet.indexOf(',');
  int b = packet.indexOf(',', a + 1);
  int c = packet.indexOf(',', b + 1);
  if (a < 0 || b < 0 || c < 0) return false;
  node = packet.substring(0, a).toInt();
  tempC = packet.substring(a + 1, b).toFloat();
  humidity = packet.substring(b + 1, c).toFloat();
  seq = (uint32_t) packet.substring(c + 1).toInt();
  if (node < 1 || node > 99) return false;
  if (tempC < -40.0 || tempC > 80.0) return false;
  if (humidity < 0.0 || humidity > 100.0) return false;
  return true;
}

void setup() {
  Serial.begin(115200);
  dht.begin();
  if (!initLoRa()) {
    Serial.println("LoRa init failed. Check SPI wiring, power, frequency, and antenna.");
    while (true) delay(10);
  }
  Serial.println(NODE_MODE_SENDER ? "LoRa sender ready." : "LoRa receiver ready.");
}

void loop() {
#if NODE_MODE_SENDER
  float tempC = dht.readTemperature();
  float humidity = dht.readHumidity();
  if (isnan(tempC) || isnan(humidity)) {
    Serial.println("DHT22 read failed; packet not sent.");
    delay(5000);
    return;
  }

  String packet = "1," + String(tempC, 1) + "," + String(humidity, 1) + "," + String(sequenceNumber++);
  LoRa.beginPacket();
  LoRa.print(packet);
  LoRa.endPacket();
  Serial.print("Sent: ");
  Serial.println(packet);
  delay(15000);
#else
  int size = LoRa.parsePacket();
  if (!size) return;
  String packet = LoRa.readString();
  int node = 0;
  float tempC = 0;
  float humidity = 0;
  uint32_t seq = 0;
  if (!parsePacket(packet, node, tempC, humidity, seq)) {
    badPackets++;
    Serial.print("Rejected malformed packet #");
    Serial.println(badPackets);
    return;
  }
  Serial.printf("Node %d seq %lu  temp %.1f C  humidity %.1f %%  RSSI %d dBm\n",
                node, (unsigned long)seq, tempC, humidity, LoRa.packetRssi());
#endif
}