使用安全 MQTT 发布和订阅 ThingSpeak 通道

此示例演示如何使用 ESP8266 板通过安全 MQTT 在 ThingSpeak™ 中记录 RSSI 数据。您可以按照注释中的指示修改代码，以使其适用于其他板或非安全 MQTT。

设置

1）创建ThingSpeak通道，如Collect Data in a New Channel所示。

2) 点击“设备”创建 MQTT 设备>ThingSpeak 页面顶部的“MQTT”，然后是“添加设备”。设置设备并将新通道添加到其授权列表时，点击“下载凭据”> “ 纯文本 ” 。详情请参见创建 ThingSpeak MQTT 设备。使用下面代码部分中保存的凭据。

3）添加ESP8266板包：

a.在“文件”下>“预设项”，在“其他板卡管理器 URL”中输入 https://arduino.esp8266.com/stable/package_esp8266com_index.json。

b.选择“工具”> 板 > 板卡管理器 。在搜索栏中输入 ESP8266 并安装该软件包。

4) 将库 WiFi.h 和 WiFiClientSecure.h 下载到 Arduino IDE。

代码

1) 定义无线网络、用于连接主板的 ThingSpeak MQTT 凭据、连接安全性，并包含适当的库。根据您的特定凭据和设置编辑此代码。

// Ensure correct credentials to connect to your WiFi Network.
char ssid[] = "ENTER_YOUR_WIFI_SSID";
char pass[] = "ENTER_YOUR_WIFI_PASSWORD";
// Ensure that the credentials here allow you to publish and subscribe to the ThingSpeak channel.
#define channelID ENTER_YOUR_THINGSPEAK_CHANNEL_NUMBER
const char mqttUserName[] = "ENTER_YOUR_MQTT_USERNAME"; 
const char clientID[] = "ENTER_YOUR_MQTT_CLIENT_ID";
const char mqttPass[] = "ENTER_YOUR_MQTT_PASSWORD";
// It is strongly recommended to use secure connections. However, certain hardware does not work with the WiFiClientSecure library.
// Comment out the following #define to use non-secure MQTT connections to ThingSpeak server. 
#define USESECUREMQTT
// Comment the following line if not using an ESP8266.
#define ESP8266BOARD

#include <PubSubClient.h>
#ifdef ESP8266BOARD
  #include <ESP8266WiFi.h>
  const char* PROGMEM thingspeak_cert_thumbprint = "9780c25078532fc0fd03dae01bfd8c923fff9878";
#else
  #include <WiFi.h>
  const char * PROGMEM thingspeak_ca_cert = \
  "-----BEGIN CERTIFICATE-----\n" \
  "MIIDxTCCAq2gAwIBAgIQAqxcJmoLQJuPC3nyrkYldzANBgkqhkiG9w0BAQUFADBs\n" \
  "MQswCQYDVQQGEwJVUzEVMBMGA1UEChMMRGlnaUNlcnQgSW5jMRkwFwYDVQQLExB3\n" \
  "d3cuZGlnaWNlcnQuY29tMSswKQYDVQQDEyJEaWdpQ2VydCBIaWdoIEFzc3VyYW5j\n" \
  "ZSBFViBSb290IENBMB4XDTA2MTExMDAwMDAwMFoXDTMxMTExMDAwMDAwMFowbDEL\n" \
  "MAkGA1UEBhMCVVMxFTATBgNVBAoTDERpZ2lDZXJ0IEluYzEZMBcGA1UECxMQd3d3\n" \
  "LmRpZ2ljZXJ0LmNvbTErMCkGA1UEAxMiRGlnaUNlcnQgSGlnaCBBc3N1cmFuY2Ug\n" \
  "RVYgUm9vdCBDQTCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAMbM5XPm\n" \
  "+9S75S0tMqbf5YE/yc0lSbZxKsPVlDRnogocsF9ppkCxxLeyj9CYpKlBWTrT3JTW\n" \
  "PNt0OKRKzE0lgvdKpVMSOO7zSW1xkX5jtqumX8OkhPhPYlG++MXs2ziS4wblCJEM\n" \
  "xChBVfvLWokVfnHoNb9Ncgk9vjo4UFt3MRuNs8ckRZqnrG0AFFoEt7oT61EKmEFB\n" \
  "Ik5lYYeBQVCmeVyJ3hlKV9Uu5l0cUyx+mM0aBhakaHPQNAQTXKFx01p8VdteZOE3\n" \
  "hzBWBOURtCmAEvF5OYiiAhF8J2a3iLd48soKqDirCmTCv2ZdlYTBoSUeh10aUAsg\n" \
  "EsxBu24LUTi4S8sCAwEAAaNjMGEwDgYDVR0PAQH/BAQDAgGGMA8GA1UdEwEB/wQF\n" \
  "MAMBAf8wHQYDVR0OBBYEFLE+w2kD+L9HAdSYJhoIAu9jZCvDMB8GA1UdIwQYMBaA\n" \
  "FLE+w2kD+L9HAdSYJhoIAu9jZCvDMA0GCSqGSIb3DQEBBQUAA4IBAQAcGgaX3Nec\n" \
  "nzyIZgYIVyHbIUf4KmeqvxgydkAQV8GK83rZEWWONfqe/EW1ntlMMUu4kehDLI6z\n" \
  "eM7b41N5cdblIZQB2lWHmiRk9opmzN6cN82oNLFpmyPInngiK3BD41VHMWEZ71jF\n" \
  "hS9OMPagMRYjyOfiZRYzy78aG6A9+MpeizGLYAiJLQwGXFK3xPkKmNEVX58Svnw2\n" \
  "Yzi9RKR/5CYrCsSXaQ3pjOLAEFe4yHYSkVXySGnYvCoCWw9E1CAx2/S6cCZdkGCe\n" \
  "vEsXCS+0yx5DaMkHJ8HSXPfqIbloEpw8nL+e/IBcm2PN7EeqJSdnoDfzAIJ9VNep\n" \
  "+OkuE6N36B9K\n" \
  "-----END CERTIFICATE-----\n";
#endif

#ifdef USESECUREMQTT
  #include <WiFiClientSecure.h>
  #define mqttPort 8883
  WiFiClientSecure client; 
#else
  #define mqttPort 1883
  WiFiClient client;
#endif

2) 定义连接参数并初始化PubSubClient实例。

const char* server = "mqtt3.thingspeak.com";
int status = WL_IDLE_STATUS; 
long lastPublishMillis = 0;
int connectionDelay = 1;
int updateInterval = 15;
PubSubClient mqttClient( client );

3）处理传入的订阅消息，订阅接收更新，并发布消息。

// Function to handle messages from MQTT subscription.
void mqttSubscriptionCallback( char* topic, byte* payload, unsigned int length ) {
  // Print the details of the message that was received to the serial monitor.
  Serial.print("Message arrived [");
  Serial.print(topic);
  Serial.print("] ");
  for (int i = 0; i < length; i++) {
    Serial.print((char)payload[i]);
  }
  Serial.println();
}

// Subscribe to ThingSpeak channel for updates.
void mqttSubscribe( long subChannelID ){
  String myTopic = "channels/"+String( subChannelID )+"/subscribe";
  mqttClient.subscribe(myTopic.c_str());
}

// Publish messages to a ThingSpeak channel.
void mqttPublish(long pubChannelID, String message) {
  String topicString ="channels/" + String( pubChannelID ) + "/publish";
  mqttClient.publish( topicString.c_str(), message.c_str() );
}

4) 连接WiFi和MQTT服务器。

// Connect to WiFi.
void connectWifi()
{
  Serial.print( "Connecting to Wi-Fi..." );
  // Loop until WiFi connection is successful
  #ifdef ESP8266BOARD
    while ( WiFi.waitForConnectResult() != WL_CONNECTED ) {
  #else
    while ( WiFi.status() != WL_CONNECTED ) {
  #endif
    WiFi.begin( ssid, pass );
    delay( connectionDelay*1000 );
    Serial.print( WiFi.status() ); 
  }
  Serial.println( "Connected to Wi-Fi." );
}

// Connect to MQTT server.
void mqttConnect() {
  // Loop until connected.
  while ( !mqttClient.connected() )
  {
    // Connect to the MQTT broker.
    if ( mqttClient.connect( clientID, mqttUserName, mqttPass ) ) {
      Serial.print( "MQTT to " );
      Serial.print( server );
      Serial.print (" at port ");
      Serial.print( mqttPort );
      Serial.println( " successful." );
    } else {
      Serial.print( "MQTT connection failed, rc = " );
      // See https://pubsubclient.knolleary.net/api.html#state for the failure code explanation.
      Serial.print( mqttClient.state() );
      Serial.println( " Will try again in a few seconds" );
      delay( connectionDelay*1000 );
    }
  }
}

5) 初始化串行数据传输，并在 setup 方法中设置 MQTT 代理详细信息。

void setup() {
  Serial.begin( 115200 );
  // Delay to allow serial monitor to come up.
  delay(3000);
  // Connect to Wi-Fi network.
  connectWifi();
  // Configure the MQTT client
  mqttClient.setServer( server, mqttPort ); 
  // Set the MQTT message handler function.
  mqttClient.setCallback( mqttSubscriptionCallback );
  // Set the buffer to handle the returned JSON. NOTE: A buffer overflow of the message buffer will result in your callback not being invoked.
  mqttClient.setBufferSize( 2048 );
  // Use secure MQTT connections if defined.
  #ifdef USESECUREMQTT
    // Handle functionality differences of WiFiClientSecure library for different boards.
    #ifdef ESP8266BOARD
      client.setFingerprint(thingspeak_cert_thumbprint);
    #else
      client.setCACert(thingspeak_ca_cert);
    #endif
  #endif
}

6）维护MQTT连接，并通过loop方法，定期向通道发布数据。

void loop() {
  // Reconnect to WiFi if it gets disconnected.
  if (WiFi.status() != WL_CONNECTED) {
      connectWifi();
  }
  
  // Connect if MQTT client is not connected and resubscribe to channel updates.
  if (!mqttClient.connected()) {
     mqttConnect(); 
     mqttSubscribe( channelID );
  }
  
  // Call the loop to maintain connection to the server.
  mqttClient.loop(); 
  
  // Update ThingSpeak channel periodically. The update results in the message to the subscriber.
  if ( abs(long(millis()) - lastPublishMillis) > updateInterval*1000) {
    mqttPublish( channelID, (String("field1=")+String(WiFi.RSSI())) );
    lastPublishMillis = millis();
  }
}

另请参阅

Publish to a Channel Field Feed | Publish to a Channel Feed

使用安全 MQTT 发布和订阅 ThingSpeak 通道

设置

代码

另请参阅

相关示例

详细信息

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