Tut11: ESP8266 I/Os Schalten per MQTT

Ziel: Daten abladen per MQTT funktioniert, jetzt fehlt noch das Schalten/Steuern über MQTT, der ESP8266 abonniert („subcribe“) Topics und schaltet je nach Inhalt.

Wir nutzen das Beispiel mqtt_esp8266 aus der Bibliothek PupSubClient , falls nicht vorhanden, nachinstallieren.
Geschaltet wird exemplarisch die interne LED.

Testen Sie das Schalten zunächst mit mosquitto_sub.

Code aus „PubSubClient“

/*
 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 -> Preferences -> Additional Boards Manager URLs":
 http://arduino.esp8266.com/stable/package_esp8266com_index.json
 - Open the "Tools -> Board -> Board Manager" and click install for the ESP8266"
 - Select your ESP8266 in "Tools -> Board"

*/

#include <ESP8266WiFi.h>
#include <PubSubClient.h>

// Update these with values suitable for your network.

const char* ssid = "xyz";
const char* password = "xyz";
const char* mqtt_server = "10.16.225.xyz";

WiFiClient espClient;
PubSubClient client(espClient);
long lastMsg = 0;
char msg[50];
int value = 0;

void setup() {
 pinMode(BUILTIN_LED, OUTPUT); // Initialize the BUILTIN_LED pin as an output
 Serial.begin(115200);
 setup_wifi();
 client.setServer(mqtt_server, 1883);
 client.setCallback(callback);
}

void setup_wifi() {

 delay(10);
 // We start by connecting to a WiFi network
 Serial.println();
 Serial.print("Connecting to ");
 Serial.println(ssid);

 WiFi.begin(ssid, password);

 while (WiFi.status() != WL_CONNECTED) {
 delay(500);
 Serial.print(".");
 }

 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 < length; i++) {
 Serial.print((char)payload[i]);
 }
 Serial.println();

 // 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 acive 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.print("Attempting MQTT connection...");
 // Attempt to connect
 if (client.connect("ESP8266Client")) {
 Serial.println("connected");
 // Once connected, publish an announcement...
 client.publish("outTopic", "hello world");
 // ... and resubscribe
 client.subscribe("inTopic");
 } else {
 Serial.print("failed, rc=");
 Serial.print(client.state());
 Serial.println(" try again in 5 seconds");
 // Wait 5 seconds before retrying
 delay(5000);
 }
 }
}
void loop() {

 if (!client.connected()) {
 reconnect();
 }
 client.loop();

 long now = millis();
 if (now - lastMsg > 2000) {
 lastMsg = now;
 ++value;
 snprintf (msg, 75, "hello world #%ld", value);
 Serial.print("Publish message: ");
 Serial.println(msg);
 client.publish("outTopic", msg);
 }
}
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