How to send data from nodeMCU to Node-red server on Google cloud platform.

workshop นี้จะทำการต่อ switch 2 ตัวเข้ากับ nodemcu และให้ส่งค่าที่ได้มาที่ Node-red server ให้รับรู้นะคับ (ส่วนจะนำไปทำอะไรต่อ เด๋วว่ากันอีกทีครับ)

เราจะต่อวงจรตามนี้นะคับ มี R 10K pull up ให้เป็น 1 กระทั่งกดสวิตซ์จึงเป็น 0 นะคับ

จากนั้นให้เปิด Arduino ide ขึ้นมาเราจะเลือกใช้ Example ‘mqtt_esp8266’ มา modify นะคับ

/*
 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>
#define CNT 5
#define LED 2
#define DOWN 4
// Update these with values suitable for your network.
const char* ssid = "Pawan";
const char* password = "a12345678"; // nodemcu ต้องเชื่อมต่อ internet 
const char* mqtt_server = "35.247.152.xxx";  //ip จาก google cloud
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(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("atthana/test", "hello from GCP of Q");
      // ... and resubscribe
      client.subscribe("atthana/test");
    } 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() {
  Serial.println("ATTHANA");
  pinMode(CNT, INPUT);  // D1 = GPIO5
  pinMode(DOWN, INPUT); // D2 is GPIO4
  pinMode(LED, OUTPUT); // LED Builtin D4 = GPIO2
  
  
  pinMode(BUILTIN_LED, OUTPUT);     // Initialize the BUILTIN_LED pin as an output
  Serial.begin(19200);
  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);
//
//  }
if(digitalRead(CNT)==LOW){
      while(digitalRead(CNT)==LOW){}
        Serial.println("D1 is pressed");
        snprintf (msg, MSG_BUFFER_SIZE, "S2");
        client.publish("atthana/shout", msg);
        digitalWrite(LED, LOW);  // LED Buildin == ON
    } else if(digitalRead(DOWN)==LOW){
      while(digitalRead(DOWN)==LOW){}
        Serial.println("D2 is pressed");
        snprintf (msg, MSG_BUFFER_SIZE, "S3");
        client.publish("atthana/shout", msg);
        digitalWrite(LED, LOW);  // LED Buildin == ON
    } else {
      digitalWrite(LED, HIGH);  // LED Buildin == OFF
    }
  
}

ใช้ mqtt in สำหรับเป็นตัว subscribe จาก nodeMCU ของเรานะคับ แน่นอนว่าจะต้องเซตค่าให้ตรงกันด้วย

เมื่อมีการกด swich ก้อจะมีค่าเข้ามาแสดงใน debug node ที่เราเชื่อมไว้

อาจจะยังงงๆเพราะอธิบายด้วยรูปภาพอย่างเดียวนะคับ เด๋วทำการทดลองเพิ่มจะมาเขียนต่อนะคับ