大家好, 今天和大家來分享, Arduino #48集, 用一塊ESP32來學 IOT (#32 Learn IOT with MQTT + ESP32) 這個影片很適合初學者來觀看學習.
影片內容主要是告訴大家, 只要手上有一塊 ESP32 和一台電腦, 就可以開始學習 IOT 了 ! 看過這個影片, 你會了解學習 IOT 一點都不難喔! 甚至可以延伸作法, EMQX MQTT web client 透過雲端EMQX來做遠端的控制!
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| 使用 MQTT 來幫助你快速完成第一個 IoT專案 |
有幾位朋友寫信來告知, MQTTLens 這個 Chrome 流覽器插件(extension) 已經無法再使用了, 所以我把這個教學的流程, 整理一下, 改用了 EMQX 本身自有的 MQTT web client 來做這個教學.
這個是一個專門為初學者來開發的一個系列, 所以會講的比較詳細, 相信各位只要仔細收看內容並進行實作, 一定會收獲滿滿滿。好, 那我們就開始吧今天的練習吧~
如果時間不夠的朋友, 也可以從以下的時間軸挑選想看的部份即可!
影片時間軸：
00:00 開始
01:03 什麼是 MQTT，它是如何運作的？
02:29 打造你的第一個MQTT IOT專案！
03:34 MQTT 程式：pubsubclient
04:27 Arduino IDE: 設定Additional Boards Manager URL
04:55 Arduino IDE 其它設定
05:22 從我的部落格中下載程式並貼在Arduino IDE
05:51 在程式中更改必要的設定
08:55 使用 EMQX MQTT web client
09:34 EMQX 簡易設定
11:39 訂閱 ESP32上的主題
14:30 從EMQX MQTT client 訂閱主題
16:52 從EMQX MQTT client 發佈主題 Stonez56/esp32s
參考資料:
- EMQX MQTT Web Client
https://www.emqx.io/online-mqtt-client/ - Pubsubclient library: https://github.com/knolleary/pubsubclient/blob/master/examples/mqtt_esp8266/mqtt_esp8266.ino
- Additional Boards Manager URL: https://arduino.esp8266.com/stable/package_esp8266com_index.json,https://dl.espressif.com/dl/package_esp32_index.json
- Source code: https://stonez56.blogspot.com/
/*
Basic ESP8266 MQTT example
This sketch demonstrates the capabilities of the pubsub library in combination
with the ESP8266 board/library.
It connects to an MQTT server then:
- publishes "hello world" to the topic "outTopic" every two seconds
- subscribes to the topic "inTopic", printing out any messages
it receives. NB - it assumes the received payloads are strings not binary
- If the first character of the topic "inTopic" is an 1, switch ON the ESP Led,
else switch it off
It will reconnect to the server if the connection is lost using a blocking
reconnect function. See the 'mqtt_reconnect_nonblocking' example for how to
achieve the same result without blocking the main loop.
To install the ESP8266 board, (using Arduino 1.6.4+):
- Add the following 3rd party board manager under "File -&nbgt; Preferences -&nbgt; Additional Boards Manager URLs":
http://arduino.esp8266.com/stable/package_esp8266com_index.json
- Open the "Tools -&nbgt; Board -&nbgt; Board Manager" and click install for the ESP8266"
- Select your ESP8266 in "Tools -&nbgt; Board"
*/
#include &nblt;WiFi.h&nbgt;
#include &nblt;PubSubClient.h&nbgt;
#include &nblt;EasyButton.h&nbgt;
#define LED 2 //built-in LED on ESP32
// Update these with values suitable for your network.
const char *ssid = "Stonez24";
const char *password = "a0101010101a";
// Define your client ID on EMQX
String mqtt_ClientID = "stonez56_IOT_Station_";
// Define your topics to subscribe / publish
const char* sub_topic = "stonez56/esp32s";
const char* pub_led_topic = "stonez56/esp32s_led_state";
const char* pub_init_topic = "stonez56/esp32s_is_back";
// EMQX broker parameters
const char *mqtt_server = "broker.emqx.io";
const char *mqtt_userName = "emqx";
const char *mqtt_password = "public";
WiFiClient espClient;
PubSubClient client(espClient);
unsigned long lastMsg = 0;
#define MSG_BUFFER_SIZE (50)
char msg[MSG_BUFFER_SIZE];
int value = 0;
void setup_wifi()
{
delay(10);
// We start by connecting to a WiFi network
Serial.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)
{
Serial.print("Message arrived [");
Serial.print(topic);
Serial.print("] ");
for (int i = 0; i &nblt; length; i++)
{
Serial.print((char)payload[i]);
}
Serial.println();
payload[length] = '\0';
String message = (char *)payload;
if (strcmp(topic, sub_topic) == 0)
{
if (message == "off")
{
digitalWrite(LED, LOW); //Turn off
client.publish(pub_led_topic, "LED off");
}
if (message == "on")
{
digitalWrite(LED, HIGH); //Turn on
client.publish(pub_led_topic, "LED on");
}
if (message == "flash")
{
digitalWrite(LED, LOW); //LED flashing 2 times
delay(200);
digitalWrite(LED, HIGH);
delay(200);
digitalWrite(LED, LOW);
delay(200);
digitalWrite(LED, HIGH);
delay(200);
digitalWrite(LED, LOW);
client.publish(pub_led_topic, "LED flashed 2 times");
}
}
/* Switch on the LED if an 1 was received as first character
// if ((char)payload[0] == '1')
// {
// digitalWrite(BUILTIN_LED, LOW); // Turn the LED on (Note that LOW is the voltage level
// // but actually the LED is on; this is because
// // it is active low on the ESP-01)
// }
// else
// {
// digitalWrite(BUILTIN_LED, HIGH); // Turn the LED off by making the voltage HIGH
// } */
}
void reconnect()
{
// Loop until we're reconnected
while (!client.connected())
{
Serial.println("Attempting EMQX MQTT connection...");
// Create a random client ID
mqtt_ClientID += String(random(0xffff), HEX);
// Attempt to connect
if (client.connect((mqtt_ClientID, mqtt_userName, mqtt_password)))
{
Serial.print(" connected with Client ID: ");
Serial.println(mqtt_ClientID);
// Once connected, publish an announcement...
client.publish(pub_init_topic, "Hi, I'm online!");
// ... and resubscribe
client.subscribe(sub_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()
{
pinMode(LED, OUTPUT); // Initialize the _LED pin as an output
digitalWrite(LED, LOW); //default ESP32 LOW is turn off
Serial.begin(115200);
setup_wifi();
client.setServer(mqtt_server, 1883);
client.setCallback(callback);
}
void loop()
{
if (!client.connected())
{
reconnect();
}
client.loop();
/* unsigned long now = millis();
// if (now - lastMsg &nbgt; 2000)
// {
// lastMsg = now;
// ++value;
// snprintf(msg, MSG_BUFFER_SIZE, "hello world #%ld", value);
// Serial.print("Publish message: ");
// Serial.println(msg);
// client.publish("stonez56/esp32s_button_pushed", msg);
// } */
}
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