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ESP32是一款由乐鑫科技（Espressif Systems）推出的双核、低功耗、集成Wi-Fi和蓝牙的单芯片微控制器。它采用了Tensilica Xtensa LX6高性能处理器，具有大量的GPIO引脚、模数转换器、SPI、I2S、UART、PWM、I2C和SD卡接口等功能，可以满足各种物联网（IoT）应用的需求。由于其高度集成和低功耗特性，ESP32广泛应用于智能家居、智能城市、工业自动化、智能健康、车联网等领域。

1.1 准备

软件：Arduino IDE
硬件：esp32-dev-module

1.2 esp32_Arduino的MQTT库安装

esp32通过MQTT协议连接到物联网平台，我们需要一个mqtt client的库，帮助我们发布订阅相关的topic。我们还需要一个JSON库，帮我们解析JSON，用来序列化和反序列化物模型的JSON数据。
在工具>管理库中，查找PubSubclient、ArduinoJSON和EspMQTTclient，并安装。

1.3 MQTT连接腾讯云的相关配置

这里使用腾讯云平台，创建物联网公共实例。
(1)填写域名和端口
${productid}.iotcloud.tencentdevices.com:1883
(2)生成username和password
要注意的是username和password是在连接到云端mqtt broker的时候需要填入的，可以通过这个在线工具生成。Hmac签名算法选择【HMAC-SHA1】。
(3)填写订阅和发布的消息，可从云平台中获得。
发送的消息指令，具体数据格式可通过云端的调试功能发送一条消息进行测试。

1.4 编写代码

#include <Arduino.h>
#include <WiFi.h>
#include "PubSubClient.h"
#include <ArduinoJson.h>
DynamicJsonDocument doc(1024);const char *ssid = "climbot";
const char *pwd  = "climbot903B";
const char *mqtt_server = "E3TGIRQYNA.iotcloud.tencentdevices.com";
const char *mqtt_username = "E3TGIRQYNA01;12010126;CT9W4;1690882370";
const char *mqtt_userpwd  = "72b711c5d7f7e1c76cfca1a785fbddfd3f744163;hmacsha1";
const char *mqtt_clientid = "E3TGIRQYNA01";
const char *mqtt_pub_topic = "$thing/up/property/E3TGIRQYNA/01";
const char *mqtt_sub_topic = "$thing/down/property/E3TGIRQYNA/01";bool power_switch;
float longtitude; 
float latitude;   
int power_percent = 0;#define REPORT_DATA_TEMPLATE "{\"method\":\"report\",\"clientToken\":\"00000001\",\"params\":{\"power_switch\":%d,\"GPS_Info\":{\"longtitude\":%f,\"latitude\":%f},\"_mesh_generic_power_percent\":%d}}"WiFiClient espClient;
PubSubClient mqttclient(espClient);
long lastMsg = 0;
char report_buf[1024];void callback(char* topic, byte* payload, unsigned int length)
{Serial.print("--->Message arrived [");Serial.print(topic);Serial.print("] ");Serial.println();Serial.print("payload [");for (int i=0;i<length;i++) {Serial.print((char)payload[i]);}Serial.println();//处理上位机的控制指令DeserializationError error = deserializeJson(doc, payload);// Test if parsing succeeds.if (error) {Serial.print("deserializeJson() failed: ");Serial.println(error.f_str());return;}else{if (doc["clientToken"]!="00000001") {if (doc["params"]["power_switch"] == 1) {Serial.print("Power On ");power_switch=1;} else {Serial.print("Power Off ");power_switch=0;}}}}void setup_wifi()
{Serial.printf("Connect to %s ", ssid);WiFi.begin(ssid, pwd);while (WiFi.status() != WL_CONNECTED) {Serial.printf(".");delay(500);}Serial.println("Connected!");Serial.print("IP address: ");Serial.println(WiFi.localIP());
}void setup() {Serial.begin(115200);setup_wifi();mqttclient.setServer(mqtt_server, 1883);// connect mqtt servermqttclient.setCallback(callback);mqttclient.setKeepAlive(65535);while (!mqttclient.connect(mqtt_clientid, mqtt_username, mqtt_userpwd)) {Serial.println("mqtt connect fail, reconnect");delay(2000);}Serial.println("mqtt connected!");// sub topicboolean ret = mqttclient.subscribe(mqtt_sub_topic);if (ret != true) {Serial.printf("mqtt subscribe topic [%s] fail\n", mqtt_sub_topic);}Serial.printf("mqtt subscribe topic [%s] ok\n", mqtt_sub_topic);
}void loop() {// client loopmqttclient.loop();// pub topiclong now = millis();if (now - lastMsg > 10000) {lastMsg = now;memset(report_buf, 0, 1024);sprintf(report_buf, REPORT_DATA_TEMPLATE, power_switch,longtitude,latitude,power_percent);Serial.println(report_buf);if (++power_percent > 100) {//模拟传感器数据power_percent = 0;}if (++longtitude > 100) {longtitude = 0;}if (++latitude > 100) {latitude = 0;}if (mqttclient.publish(mqtt_pub_topic, report_buf)) {Serial.printf("mqtt publish topic [%s] ok\n", mqtt_pub_topic);} else {Serial.printf("mqtt publish topic [%s] fail\n", mqtt_pub_topic);}}
}

1.5 烧录和测试

点击下载按钮，待下载完成后，打开串口监视器可看到打印的数据。打开腾讯云平台可查看设备在线状态。