Arduino网络编程实战-WiFi篇-MQTT客户端

MQTT客户端

ESP-01/ESP-01 WiFi模块是由安信可科技开发，该模块核心处理器为ESP8266，在较小尺寸封装中集成了业界领先的Tensilica L06超低功耗32位微处理器（MCU）,带有16位精简模式，主频支持80MHz和160MHz，支持RTOS，集成WiFi MAC/BB/RF/PA/LNA，板载天线。参考

该模块支持标准的IEEE802.11 b/g/n 协议，完整的TCP/IP协议栈。用户可以使用该模块为现有的设备添加联网功能，也可以构建独立的网络控制器。参考

ESP8266是高性能无线SOC，以最低成本提供最大实用性，为WiFi功能嵌入其他系统提供无限可能。参考

1、硬件准备

Arduino Mega2560 开发板一块
ESP-01/ESP-01s模块一块
ESP-01/ESP-01s转接板一块（请在某宝上搜索购买）
ESP-01/ESP-01s固件烧录器一个（请在某宝上搜索购买）
杜邦线若干
Arduino开发板数据线一条
USB串口数据线一条

1）通过ESP-01/ESP-01s固件烧写器将ESP-AT的固件烧写到ESP-01/ESP-01s模块中

2）ESP-01/ESP-01s模块插入ESP-01/ESP-01s转接板

3）ESP-01/ESP-01s WiFi转接板与Arduino Mega2560硬件接线如下：

Arduino Mega2560 RX3<–-> ESP-01/ESP-01s TX
Arduino Mega2560 TX3<–-> ESP-01/ESP-01s RX
Arduino Mega2560 GND<–-> ESP-01/ESP-01s GND
Arduino Mega2560 5V<–-> ESP-01/ESP-01s VCC

2、软件准备

Arduino IDE
ESP-AT指令支持库：ESP8266_AT_WebServer
ESP-AT指令支持库：ESP_AT_Lib
串口调试软件
网络调试软件（推荐使用通信猫)
MQTT服务器及客户端软件：Mosquitto

3、代码实现

// 定义与ESP-01模块通信串口
#define EspSerial Serial3
// 在AVR环境中使用ESP AT指令
#define ESP\_AT\_USE\_AVR true
// 开发板类型
#define BOARD\_TYPE "AVR Mega2560"
// 开发板名称
#define BOARD\_NAME BOARD\_TYPE
// 调试串口
#define DEBUG\_ESP8266\_AT\_WEBSERVER\_PORT Serial
// 扩展板类型
#define SHIELD\_TYPE "ESP8266-AT & ESP8266\_AT\_WebServer Library" 

// 调试输出日志级别 0 至 4
#define \_ESP\_AT\_LOGLEVEL\_ 0

#include <ESP8266\_AT\_WebServer.h>

char ssid[] = "\*\*\*\*";      
char pass[] = "\*\*\*\*";        
// 无线状态
int status = WL_IDLE_STATUS;    
int reqCount = 0;

#include <PubSubClient.h>

const char \*ID        = "MQTTClient\_SSL-Client";  // Name of our device, must be unique
const char \*TOPIC     = "MQTT\_Pub";               // Topic to subcribe to
const char \*subTopic  = "MQTT\_Sub";               // Topic to subcribe to

IPAddress mqttServer(192, 168, 0, 131);


void callback(char\* topic, byte\* payload, unsigned int length) 
{
  Serial.print("Message arrived [");
  Serial.print(topic);
  Serial.print("] ");
  
  for (unsigned int i = 0; i < length; i++) 
  {
    Serial.print((char)payload[i]);
  }
  
  Serial.println();
}

ESP8266_AT_Client  espClient;
PubSubClient    client(mqttServer, 1883, callback, espClient);

void reconnect()
{
  static String data = "Hello from MQTTClient\_Basic on " + String(BOARD_NAME);
  
  // Loop until we're reconnected
  while (!client.connected())
  {
    Serial.print("Attempting MQTT connection to ");
    Serial.print(mqttServer);

    // Attempt to connect
    if (client.connect(ID, "try", "try"))
    {
      Serial.println("...connected");
      
      // Once connected, publish an announcement...
      client.publish(TOPIC, data.c\_str());
      
      client.subscribe(subTopic);
      // for loopback testing
      client.subscribe(TOPIC);
    }
    else
    {
      Serial.print("...failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");

      // Wait 5 seconds before retrying
      delay(5000);
    }
  }
}

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

  Serial.print(F("\nStarting ConnectWPA on "));
  Serial.print(BOARD_NAME);
  Serial.print(F(" with "));
  Serial.println(SHIELD_TYPE); 
  Serial.println(ESP8266_AT_WEBSERVER_VERSION);

  // 初始化ESP模块
  EspSerial.begin(115200);
  WiFi.init(&EspSerial);

  Serial.println(F("WiFi shield init done"));

  // 检查ESP-01与开发板连接状态
  if (WiFi.status() == WL_NO_SHIELD)
  {
    Serial.println(F("WiFi shield not present"));
    while (true);
  }

  // 连接网络
  while ( status != WL_CONNECTED)
  {
    Serial.print(F("Connecting to WPA SSID: "));
    Serial.println(ssid);
    
    // 连接WiFi热点
    status = WiFi.begin(ssid, pass);
  }

  Serial.print(F("You're connected to the network, IP = "));
  Serial.println(WiFi.localIP());
  client.setServer(mqttServer, 1883);
  client.setCallback(callback);
}

#define MQTT\_PUBLISH\_INTERVAL\_MS 5000L

String data         = "Hello from MQTTClient\_Basic on " + String(BOARD_NAME) + " with " + String(SHIELD_TYPE);
const char \*pubData = data.c\_str();

unsigned long lastMsg = 0;

void loop()
{
  static unsigned long now;
  
  if (!client.connected()) 
  {
    reconnect();
  }

  // Sending Data
  now = millis();
  
  if (now - lastMsg > MQTT_PUBLISH_INTERVAL_MS)
  {
    lastMsg = now;

    if (!client.publish(TOPIC, pubData))
    {
      Serial.println("Message failed to send.");
    }

    Serial.print("Message Send : ");
    Serial.print(TOPIC);
    Serial.print(" => ");
    Serial.println(data);
  }
  
  client.loop();
}