ESP32 — MQTT 基本範例 (MQTT Box)
介紹
本課程將展示WOKWI ESP32 模擬的基本MQTT協定使用。
- 每兩秒向主題“alex9ufo/outTopic”發布“hello world”。
- 訂閱主題“alex9ufo/inTopic”，列印收到的所有訊息。
- 它假設接收到的有效負載是字串而不是二進位。
- 如果訂閱的訊息為“ON”，則點亮板載LED。
- 如果訂閱的訊息為“OFF”，則熄滅板載LED。
準備：
- https://wokwi.com/projects/new/esp32 。 wokwi 註冊
- MQTTbox 下載 安裝
- sketch.ion程式。
#include <WiFi.h>
#include "PubSubClient.h"
// WiFi
char ssid[]="Wokwi-GUEST";
char pass[]="";
// MQTT Broker
const char *mqtt_broker = "broker.mqtt-dashboard.com";//"broker.emqx.io";//Public Broker
const char *mqtt_username = "hivemqtt";
const char *mqtt_password = "public";
const int mqtt_port = 1883;
// App Protcol ---> Port
const char *topic_publish = "alex9ufo/outTopic";//Topic ESP32 Pusblish
const char *topic_subsrcibe = "alex9ufo/inTopic";//Topic ESp32 Subscribe
WiFiClient hamada;//WIFI Opject
PubSubClient client(hamada);//OOP
void callback(char *topic, byte *payload, unsigned int length);
#define LED 2
bool ledState=false;
unsigned long lastMsg = 0;
#define MSG_BUFFER_SIZE (50)
char msg[MSG_BUFFER_SIZE];
int value = 0;
void reconnect() {
// Loop until we're reconnected
while (!client.connected()) {
Serial.print("Attempting MQTT connection...");
// Create a random client ID
String clientId = "ESP32Client-";
clientId += String(random(0xffff), HEX);
// Attempt to connect
if (client.connect(clientId.c_str())) {
Serial.println("connected");
// Once connected, publish an announcement...
client.publish(topic_publish, "Hello world.....");
client.subscribe(topic_subsrcibe);
} 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(){
// Setting LED pin as output
pinMode(LED, OUTPUT);
digitalWrite(LED, LOW); // Turn off the LED initially
//Open a serial connection to display program results and establish a connection to the Wi-Fi network.
// Set software serial baud to 115200;
Serial.begin(115200);
// Connecting to a Wi-Fi network
WiFi.begin(ssid, pass);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.println("Connecting to WiFi..");
}
Serial.println("Connected to the Wi-Fi network");
// Utilize PubSubClient to establish a connection with the MQTT broker.
//connecting to a mqtt broker
Serial.println("Before Connect MQTT");
//Broker Configuration
client.setServer(mqtt_broker, mqtt_port);
while (!client.connected()) {
String client_id = "esp32-client-";
client_id =client_id+ String(WiFi.macAddress());
//consloe.log("x"+"y");//xy
//ESP32-ID -----> esp32-client-macaddress
//variable.c_str()--->char [] , String
Serial.printf("The client %s connects to the public MQTT broker\n", client_id.c_str());
if (client.connect(client_id.c_str(), mqtt_username, mqtt_password)) {
Serial.println("Public MQTT broker connected");
} else {
Serial.print("failed with state ");
Serial.print(client.state());//1 , 2 , 5
delay(2000);
}
}
Serial.println("After Connect MQTT");
client.publish(topic_publish, "Hello world.....");
client.subscribe(topic_subsrcibe);
client.setCallback(callback);
}
void loop() {
if (!client.connected()) {
reconnect();
}
client.loop();
unsigned long now = millis();
if (now - lastMsg > 10000) {
lastMsg = now;
++value;
snprintf (msg, MSG_BUFFER_SIZE, "hello world #%ld", value);
Serial.print("Publish message: ");
Serial.println(msg);
client.publish(topic_publish, msg);
}
}
void callback(char* topic, byte* message, unsigned int length) {
printPayload(topic, message, length);
}
void printPayload(char* topic, byte* message, unsigned int length) {
// Printing Received Message
Serial.print("Message received on topic: ");
Serial.println(topic);
String messageTemp;
for(int i=0; i<length; i+=1) {
messageTemp += (char)message[i];
}
if(String(topic) == "alex9ufo/inTopic"){
Serial.println("alex9ufo/inTopic");
if(messageTemp=="ON"){
Serial.println("Led ON");
digitalWrite(LED,HIGH);
}
if(messageTemp=="OFF"){
Serial.println("Led OFF");
digitalWrite(LED,LOW);
}
}
Serial.println(messageTemp);
}
- diagram.json程式 (電路圖)。
{
"version": 1,
"author": "Anonymous maker",
"editor": "wokwi",
"parts": [
{ "type": "wokwi-esp32-devkit-v1", "id": "esp", "top": -321.7, "left": -168.2, "attrs": {} },
{
"type": "wokwi-resistor",
"id": "r1",
"top": -225.6,
"left": 37.85,
"rotate": 90,
"attrs": { "value": "1000" }
},
{
"type": "wokwi-led",
"id": "led1",
"top": -310.8,
"left": 32.6,
"attrs": { "color": "red" }
}
],
"connections": [
[ "esp:TX0", "$serialMonitor:RX", "", [] ],
[ "esp:RX0", "$serialMonitor:TX", "", [] ],
[ "led1:C", "esp:GND.1", "black", [ "v0" ] ],
[ "r1:1", "led1:A", "red", [ "h0" ] ],
[ "esp:D2", "r1:2", "red", [ "h0" ] ]
],
"dependencies": {}
}
- Library manager --> Project Libaries --> Installed Libraries 。
MQTTBox設定：
broker.mqtt-dashboard.com:1883/ws
mqtt / tcp
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