ESP-32与LoRa RA-02模块收发循环异常问题求助

问题描述 #

我拥有两套ESP-32与Ra-02 LoRa模块，希望实现节点间消息发送并获取回复确认。目前Node1发送的消息可到达Node2，但Node2向Node1的回复无法被接收，请问我遗漏了什么配置？

Node1 原始代码 #

#include <SPI.h>
#include <LoRa.h>

#define SCK 18
#define MISO 19
#define MOSI 23
#define NSS 5
#define RESET 14
#define DIO0 26

void setup() {
  Serial.begin(115200);
  while (!Serial);

  LoRa.setPins(NSS, RESET, DIO0);
  if (!LoRa.begin(433E6)) {
    Serial.println("Starting LoRa failed!");
    while (1);
  }

  Serial.println("LoRa Transmitter");
}

void loop() {
  String message = "Hello";
  Serial.print("Sending: ");
  Serial.println(message);
  
  LoRa.beginPacket();
  LoRa.print(message);
  LoRa.endPacket();

  delay(100);

  // Wait for acknowledgment
  unsigned long startMillis = millis();
  unsigned long timeout = 2000; // 2 seconds timeout
  String response = "";

  LoRa.idle(); // Ensure the module is in idle state before entering the loop
  while (millis() - startMillis < timeout) {
    int packetSize = LoRa.parsePacket();
    if (packetSize) {
      while (LoRa.available()) {
        response += (char)LoRa.read();
      }
      break; // Exit the loop once a packet is received
    }
  }

  if (response != "") {
    Serial.print("Received response: ");
    Serial.println(response);
  } else {
    Serial.println("No response received");
  }

  delay(5000);
}

Node2 原始代码 #

#include <SPI.h>
#include <LoRa.h>

#define SCK 18
#define MISO 19
#define MOSI 23
#define NSS 5
#define RESET 14
#define DIO0 26

void setup() {
  Serial.begin(115200);
  while (!Serial);

  LoRa.setPins(NSS, RESET, DIO0);
  if (!LoRa.begin(433E6)) {
    Serial.println("Starting LoRa failed!");
    while (1);
  }

  Serial.println("LoRa Receiver");
}

void loop() {
  int packetSize = LoRa.parsePacket();
  if (packetSize) {
    String incoming = "";
    while (LoRa.available()) {
      incoming += (char)LoRa.read();
    }

    Serial.print("Received: ");
    Serial.println(incoming);

    // Send acknowledgment
    String response = incoming + ":ack";
    Serial.print("Sending: ");
    Serial.println(response);
    
    LoRa.beginPacket();
    LoRa.print(response);
    LoRa.endPacket();
  }
}

问题原因与解决方案 #

1. 未统一LoRa核心通信参数 #

LoRa模块的双向通信必须保证所有参数完全一致，仅设置频率不足以确保兼容。不同版本的LoRa库默认参数可能存在差异，导致Node2的回复无法被Node1解调。

修复：在两个节点的setup()中添加统一参数配置

在LoRa.begin(433E6)之后添加以下代码（两个节点必须完全相同）：

// 统一LoRa通信参数，确保节点间兼容
LoRa.setSpreadingFactor(7);    // 扩频因子：6-12，数值越高距离越远、速率越低
LoRa.setSignalBandwidth(125E3); // 带宽：可选125E3/250E3/500E3
LoRa.setCodingRate4(5);        // 编码率：5-8
LoRa.setTxPower(17);           // RA-02最大支持20dBm，根据实际场景调整

2. Node1的接收逻辑冗余且干扰模式切换 #

Node1发送完数据包后调用LoRa.idle()是冗余操作，LoRa.parsePacket()会自动将模块切换到接收模式，额外的idle()可能导致模块无法及时进入接收状态。

修复：简化Node1的接收逻辑

修改Node1中等待回复的代码段：

// Wait for acknowledgment
unsigned long startMillis = millis();
unsigned long timeout = 2000; // 2 seconds timeout
String response = "";

// 移除LoRa.idle()，parsePacket会自动切换到接收模式
while (millis() - startMillis < timeout) {
  int packetSize = LoRa.parsePacket();
  if (packetSize > 0) {
    response = ""; // 清空缓冲区，避免残留旧数据
    while (LoRa.available()) {
      response += (char)LoRa.read();
    }
    Serial.print("Received response: ");
    Serial.println(response);
    break;
  }
}

if (response == "") {
  Serial.println("No response received");
}

3. 可选：优化Node2发送后的状态 #

Node2发送回复后，可以强制模块回到接收模式，避免影响后续数据包接收：
在Node2的LoRa.endPacket()之后添加：

LoRa.receive(); // 强制切换回接收模式

4. 硬件检查 #

• 确认两个RA-02模块都正确连接了外接天线，无天线会导致信号衰减严重，无法完成双向通信。
• 核对ESP32与RA-02的SPI引脚接线是否与代码中定义的一致（SCK、MISO、MOSI、NSS、RESET、DIO0）。

修改后的完整代码示例 #

Node1 修改后代码 #

#include <SPI.h>
#include <LoRa.h>

#define SCK 18
#define MISO 19
#define MOSI 23
#define NSS 5
#define RESET 14
#define DIO0 26

void setup() {
  Serial.begin(115200);
  while (!Serial);

  LoRa.setPins(NSS, RESET, DIO0);
  if (!LoRa.begin(433E6)) {
    Serial.println("Starting LoRa failed!");
    while (1);
  }

  // 统一LoRa通信参数
  LoRa.setSpreadingFactor(7);
  LoRa.setSignalBandwidth(125E3);
  LoRa.setCodingRate4(5);
  LoRa.setTxPower(17);

  Serial.println("LoRa Transmitter");
}

void loop() {
  String message = "Hello";
  Serial.print("Sending: ");
  Serial.println(message);
  
  LoRa.beginPacket();
  LoRa.print(message);
  LoRa.endPacket();

  delay(100);

  // Wait for acknowledgment
  unsigned long startMillis = millis();
  unsigned long timeout = 2000;
  String response = "";

  while (millis() - startMillis < timeout) {
    int packetSize = LoRa.parsePacket();
    if (packetSize > 0) {
      response = "";
      while (LoRa.available()) {
        response += (char)LoRa.read();
      }
      Serial.print("Received response: ");
      Serial.println(response);
      break;
    }
  }

  if (response == "") {
    Serial.println("No response received");
  }

  delay(5000);
}

Node2 修改后代码 #

#include <SPI.h>
#include <LoRa.h>

#define SCK 18
#define MISO 19
#define MOSI 23
#define NSS 5
#define RESET 14
#define DIO0 26

void setup() {
  Serial.begin(115200);
  while (!Serial);

  LoRa.setPins(NSS, RESET, DIO0);
  if (!LoRa.begin(433E6)) {
    Serial.println("Starting LoRa failed!");
    while (1);
  }

  // 统一LoRa通信参数，与Node1完全一致
  LoRa.setSpreadingFactor(7);
  LoRa.setSignalBandwidth(125E3);
  LoRa.setCodingRate4(5);
  LoRa.setTxPower(17);

  Serial.println("LoRa Receiver");
}

void loop() {
  int packetSize = LoRa.parsePacket();
  if (packetSize) {
    String incoming = "";
    while (LoRa.available()) {
      incoming += (char)LoRa.read();
    }

    Serial.print("Received: ");
    Serial.println(incoming);

    // Send acknowledgment
    String response = incoming + ":ack";
    Serial.print("Sending: ");
    Serial.println(response);
    
    LoRa.beginPacket();
    LoRa.print(response);
    LoRa.endPacket();
    LoRa.receive(); // 强制回到接收模式
  }
}

内容的提问来源于stack exchange，提问作者Logu