Differences

This shows you the differences between two versions of the page.

--- latinet:unicaes:workshops:communication-23 [2023/08/29 20:33] – jan.sonntag
+++ latinet:unicaes:workshops:communication-23 [2024/03/23 19:02] (current) – ↷ Links adapted because of a move operation 47.128.112.114
@@ Line 8: / Line 8: @@
 ===== 2. ESP8266 and WiFi =====
-Next, we'll take a closer look at connecting the ESP8266 to WiFi. This step is crucial for enabling wireless communication, allowing your devices to seamlessly interact with the digital world.
+Next, we'll take a closer look at connecting the ESP8266 to WiFi. This step is crucial for enabling wireless communication, allowing your devices to seamlessly interact with the digital world.fi
+<file c++ wifi-http-api-example.ino>
+#include <ESP8266WiFi.h>
+#include <WiFiClientSecure.h>
+// Replace with your WiFi credentials
+const char* ssid = "wifi-ssid";
+const char* password = "wifi-password";
+// Replace with your API details
+const char* apiHost = "weather.eolab.de";
+const char* apiEndpoint = "/api";
+// Create an instance of WiFiClientSecure
+WiFiClientSecure client;
+void setup() {
+  Serial.begin(115200);
+  // Connect to Wi-Fi
+  WiFi.begin(ssid, password);
+  Serial.print("Connecting to ");
+  Serial.print(ssid);
+  while (WiFi.status() != WL_CONNECTED) {
+    delay(1000);
+    Serial.print(".");
+  }
+  Serial.println("\nConnected to WiFi");
+  // Set the client to verify the server's certificate
+  client.setInsecure();
+  // Give the client a chance to perform the handshake
+  delay(1000);
+}
+void loop() {
+  if (WiFi.status() == WL_CONNECTED) {
+    // Make an HTTPS GET request
+    client.connect(apiHost, 443); // Use port 443 for HTTPS
+    client.print(String("GET ") + apiEndpoint + " HTTP/1.1\r\n" +
+                 "Host: " + apiHost + "\r\n" +
+                 "Connection: close\r\n\r\n");
+    // Wait for the response
+    while (client.connected()) {
+      String line = client.readStringUntil('\n');
+      if (line == "\r") {
+        Serial.println("Headers received");
+        break;
+      }
+    }
+    // Print the response from the server
+    while (client.available()) {
+      String response = client.readStringUntil('\n');
+      Serial.println(response);
+    }
+    client.stop();
+  }
+  // Wait for a while before making the next request
+  delay(5000);
+}
+</file>
+In this example code, you will first of all connect to a WiFi network and then try to access a predefined API. This API is the root of our public weather station API. You can find out more about the project right here: [[eolab:weather_station:kamp-lintfort:start|HSRW Weather Station at Campus Kamp-Lintfort]]
 ===== 3. Our first MQTT Publish =====
 Stepping ahead, you'll have the chance to implement your first MQTT publish from the ESP8266. While the following example provides a static demonstration, we encourage you to take it a step further by incorporating one of the sensors available to you.
+PubSubClient Library: [[https://github.com/knolleary/pubsubclient|PubSubClient by knolleary]]
+<file c++ mqtt-publish.ino>
+/*
+ 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 defined as outTopic every two seconds
+ 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.
+*/
+#include <ESP8266WiFi.h>
+#include <PubSubClient.h>
+#define MSG_BUFFER_SIZE	(50)
+// Update these with values suitable for your network and mqtt broker
+const char* ssid = "";
+const char* password = "";
+const char* mqtt_server = "broker.hivemq.com";
+const char* outTopic = "unicaes/workshop/2023/jan";
+const char* inTopic = "unicaes/workshop/2023/to-jan";
+// Set up of some needed variables
+WiFiClient espClient;
+PubSubClient client(espClient);
+unsigned long lastMsg = 0;
+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 reconnect() {
+  // Loop until we're reconnected
+  while (!client.connected()) {
+    Serial.print("Attempting MQTT connection...");
+    // Create a random client ID
+    String clientId = "ESP8266Client-";
+    clientId += String(random(0xffff), HEX);
+    // Attempt to connect
+    if (client.connect(clientId.c_str())) {
+      Serial.println("connected");
+      // Once connected, publish an announcement...
+      client.publish(outTopic, "hello world");
+    } 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(BUILTIN_LED, OUTPUT);     // Initialize the BUILTIN_LED pin as an output
+  Serial.begin(115200);
+  setup_wifi();
+  client.setServer(mqtt_server, 1883);
+}
+void loop() {
+  if (!client.connected()) {
+    reconnect();
+  }
+  client.loop();
+  unsigned long now = millis();
+  if (now - lastMsg > 2000) {
+    lastMsg = now;
+    ++value;
+    snprintf (msg, MSG_BUFFER_SIZE, "hello world #%ld", value);
+    Serial.print("Publish message: ");
+    Serial.println(msg);
+    client.publish(outTopic, msg);
+  }
+}
+</file>
 ===== 4. Subscribe =====
 Now, let's move on to an essential aspect of our workshop. We'll guide you through the process of subscribing to an MQTT topic. This step is a practical gateway to interactive IoT applications. You'll learn how to exchange MQTT messages between devices, potentially triggering actions like LED reactions or serial outputs. While we'll provide initial guidance, feel free to explore further and experiment with this dynamic feature.
+<file c++ mqtt-subscribe-example.ino>
+/*
+ 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 defined as outTopic every two seconds
+  - subscribes to the topic defined as inTopic, printing out any messages
+    it receives. NB - it assumes the received payloads are strings not binary
+  - If the first character of the topic defined as 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.
+*/
+#include <ESP8266WiFi.h>
+#include <PubSubClient.h>
+// Update these with values suitable for your network and mqtt broker
+const char* ssid = "";
+const char* password = "";
+const char* mqtt_server = "broker.hivemq.com";
+const char* outTopic = "unicaes/workshop/2023/jan";
+const char* inTopic = "unicaes/workshop/2023/to-jan";
+// Set up of some needed variables
+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 < 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 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.print("Attempting MQTT connection...");
+    // Create a random client ID
+    String clientId = "ESP8266Client-";
+    clientId += String(random(0xffff), HEX);
+    // Attempt to connect
+    if (client.connect(clientId.c_str())) {
+      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 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 loop() {
+  if (!client.connected()) {
+    reconnect();
+  }
+  client.loop();
+  unsigned long now = millis();
+  if (now - lastMsg > 2000) {
+    lastMsg = now;
+    ++value;
+    snprintf (msg, MSG_BUFFER_SIZE, "hello world #%ld", value);
+    Serial.print("Publish message: ");
+    Serial.println(msg);
+    client.publish(outTopic, msg);
+  }
+}
+</file>
 ===== Recording =====