ESP8266智能家居（3）——单片机数据发送到mqtt服务器

1.主要思想

前期已学习如何用ESP8266连接WIFI，并发送数据到服务器。现在只需要在单片机与nodeMCU之间建立起串口通信，这样单片机就可以将传感器测到的数据：光照，温度，湿度等等传递给8266了，然后8266再对数据进行打包，发送到服务器。

51单片机和nodeMCU的连线方式如下

它们串口的两根线交叉连接，二者的USB供电端一起接在电脑的USB口上。如果它们不是用的同一套供电系统，就需要注意共地的问题！

2.代码设计

51单片机的主体代码大致如下;

主要就是测量一些数据，然后通过串口发送到nodeMCU

nodeMCU的代码如下：

#include <ESP8266WiFi.h>
#include <PubSubClient.h>
#include <ArduinoJson.h>
const char* ssid = "iPhone";          //WIFI名称   自己补上你的WIFI
const char* password = "12345678";      //WIFI密码    自己补上你的密码
const char* mqtt_server = "broker-cn.emqx.io";      //mqtt服务器地址 （IP/域名）  不改
const char *pubTopic="my_pubtopic";
const char *subTopic="my_subtopic";WiFiClient espClient;
PubSubClient client(espClient);char information[80]="";
int value = 0;void setup_wifi() {delay(10);// We start by connecting to a WiFi networkSerial.println();Serial.print("Connecting to ");Serial.println(ssid);WiFi.mode(WIFI_STA);WiFi.begin(ssid, password);while (WiFi.status() != WL_CONNECTED) {delay(500);Serial.print(".");}randomSeed(micros());Serial.println("");Serial.println("WiFi connected");Serial.println("IP address: ");Serial.println(WiFi.localIP());
}void callback(char* topic, byte* payload, unsigned int length) {String cmd="";for (int i = 0; i < length; i++) {cmd+=(char)payload[i];}const size_t capacity = JSON_OBJECT_SIZE(1) + 10;   //计算buffer的大小   ...SIZE（1）表明buffer中只有一个对象DynamicJsonBuffer jsonBuffer(capacity);           //创建动态的jsonbufferJsonObject& root = jsonBuffer.parseObject(cmd);     //解析Json对象字符串Serial.println("get");if(root.containsKey("led"))      //判断是否包含某个键{int led = root["led"]; if(led==1){Serial.println("1");}elseSerial.println("2");}if(root.containsKey("beep"))      //判断是否包含某个键{int beep = root["beep"]; if(beep==1){Serial.println("3");}elseSerial.println("4");}
}void reconnect() {// Loop until we're reconnectedwhile (!client.connected()) {Serial.print("Attempting MQTT connection...");// Create a random client IDString clientId = "ESP8266Client-";clientId += String(random(0xffff), HEX);// Attempt to connectif (client.connect(clientId.c_str())) {Serial.println("connected");// Once connected, publish an announcement...client.publish(pubTopic, "hello world");// ... and resubscribeclient.subscribe(subTopic);} else {Serial.print("failed, rc=");Serial.print(client.state());Serial.println(" try again in 5 seconds");// Wait 5 seconds before retryingdelay(5000);}}
}void setup() {Serial.begin(9600);setup_wifi();client.setServer(mqtt_server, 1883);client.setCallback(callback);
}void loop() {if (!client.connected()) {reconnect();}client.loop();value=0;while(!Serial.available());    //等待数据传送过来，若没有数据，一直等待，即执行到本行不向下执行while(Serial.available()){    information[value]=(char)Serial.read();  value++;  delay(3);}client.publish(pubTopic, information); Serial.print(information);// }
}