📡 ESP32 LoRa 无线通信：SX1278 远距离数据传输实战

// ========== 发送端 (Sender) ==========
#include <SPI.h>
#include <LoRa.h>

#define SS      14
#define RST     2
#define DIO0    26
#define FREQ    433E6   // 433 MHz

int packetCounter = 0;

void setup() {
  Serial.begin(115200);
  delay(1000);
  Serial.println("🚀 LoRa Sender 启动中...");

  LoRa.setPins(SS, RST, DIO0);
  if (!LoRa.begin(FREQ)) {
    Serial.println("❌ LoRa 初始化失败！检查接线");
    while (1);
  }
  LoRa.setSpreadingFactor(7);   // SF7 = 最快
  LoRa.setSignalBandwidth(125E3); // 125 kHz
  LoRa.setCodingRate4(5);         // 4/5
  Serial.println("✅ LoRa 初始化成功！");
}

void loop() {
  char msg[64];
  sprintf(msg, "Hello #%d | RSSI将在接收端显示", packetCounter);

  LoRa.beginPacket();
  LoRa.print(msg);
  LoRa.endPacket();

  Serial.printf("📤 发送 #%d: %s\n", packetCounter, msg);
  packetCounter++;
  delay(3000);
}

// ========== 接收端 (Receiver) ==========
#include <SPI.h>
#include <LoRa.h>

#define SS      14
#define RST     2
#define DIO0    26
#define FREQ    433E6
#define LED     2  // 板载 LED

void setup() {
  Serial.begin(115200);
  pinMode(LED, OUTPUT);
  digitalWrite(LED, LOW);
  delay(1000);
  Serial.println("📡 LoRa Receiver 启动中...");

  LoRa.setPins(SS, RST, DIO0);
  if (!LoRa.begin(FREQ)) {
    Serial.println("❌ LoRa 初始化失败！");
    while (1);
  }
  LoRa.setSpreadingFactor(7);
  LoRa.setSignalBandwidth(125E3);
  LoRa.setCodingRate4(5);
  Serial.println("✅ 等待数据...");
}

void loop() {
  int packetSize = LoRa.parsePacket();
  if (packetSize == 0) return;

  // 读取数据
  char buf[128] = {0};
  int i = 0;
  while (LoRa.available() && i < 127) {
    buf[i++] = (char)LoRa.read();
  }
  buf[i] = '\0';

  // 获取信号质量
  int rssi = LoRa.packetRssi();
  float snr = LoRa.packetSnr();

  Serial.printf("📥 收到: %s | RSSI:%d dBm | SNR:%.1f dB\n",
                  buf, rssi, snr);

  // LED 闪烁确认
  digitalWrite(LED, HIGH); delay(100);
  digitalWrite(LED, LOW);
}

// 发送后等待确认
LoRa.beginPacket();
LoRa.print("DATA:26.5,65.2");
LoRa.endPacket(true);  // true = 发送完后立即进入接收模式

// 等待 500ms 内的 ACK
unsigned long start = millis();
while (millis() - start < 500) {
  if (LoRa.parsePacket()) {
    String ack = LoRa.readString();
    if (ack == "ACK") {
      Serial.println("✅ 收到确认");
      break;
    }
  }
}

// 节点端 — 带 ID 发送
#define NODE_ID 3
char msg[64];
sprintf(msg, "NODE:%d|T:%.1f|H:%.1f", NODE_ID, temp, hum);
LoRa.beginPacket();
LoRa.print(msg);
LoRa.endPacket();

// 网关端 — 解析来源
String payload = LoRa.readString();
int nodeId;
float temp, hum;
sscanf(payload.c_str(), "NODE:%d|T:%f|H:%f", &nodeId, &temp, &hum);
Serial.printf("节点%d → 温度%.1f°C 湿度%.1f%%\n", nodeId, temp, hum);