Back to Parent

// This value will store the last time we published an event
long lastPublishedAt = 0;
// this is the time delay before we should publish a new event
// from this device
int publishAfter = 10000;

bool shouldActivate = false;

int solPin = D4;

int buttonPin = D2;

void setup()

  // We'll want to subscribe to an event thats fairly unique

  // From the Particle Docs
  // A subscription works like a prefix filter.
  // If you subscribe to "foo", you will receive any event
  // whose name begins with "foo", including "foo", "fool",
  // "foobar", and "food/indian/sweet-curry-beans".

  // Basically this will match any event that starts with 'db2018/paired/'
  // This is a feature we'll useto figure out if our event comes from
  // this device or another (see publishMyEvent below)

  Particle.subscribe(  "diot/2020/paired/" , handleSharedEvent );
  pinMode(solPin, OUTPUT);
  pinMode(buttonPin , INPUT_PULLUP); // sets pin as input


void loop()
    // publish my event
    // you'll want some more complex stuff here
    int buttonState = digitalRead( buttonPin );

    // when the button is not pushed we'll get a HIGH
    // if LOW, send the event

    if( buttonState == LOW )
        // turn the LED On
    // delay for a bit

void publishMyEvent()
  // Remember that a device can publish at rate of about 1 event/sec,
  // with bursts of up to 4 allowed in 1 second.
  // Back to back burst of 4 messages will take 4 seconds to recover.
  // So we want to limit the amount of publish events that happen.

  // check that it's been 10 secondds since our last publish
  if( lastPublishedAt + publishAfter < millis() )
      // Remember our subscribe is matching  "db2018/paired/"
      // We'll append the device id to get more specific
      // about where the event came from

      // System.deviceID() provides an easy way to extract the device
      // ID of your device. It returns a String object of the device ID,
      // which is used to identify your device.

      String eventName = "diot/2020/paired/" + System.deviceID();

      // now we have something like "diot/2019/paired/0123456789abcdef"
      // and that corresponds to this devices info

      // then we share it out
      Particle.publish( eventName, "data goes here" );

      // And this will get shared out to all devices using this code

      // we just pubished so capture this.
      lastPublishedAt = millis();


// Our event handlde requires two bits of information
// This gives us:
// A character array that consists of the event name
// A character array that contains the data published in the event we're responding to.
void handleSharedEvent(const char *event, const char *data)
    // Now we're getting ALL events published using "db2018/paired/"
    // This includes events from this device.
    // So we need to ignore any events that we sent.

    // Let's check the event name
    String eventName = String( event ); // convert to a string object
    // This gives us access to a bunch of built in methods
    // Like indexOf()
    // Locates a character or String within another String.
    // By default, searches from the beginning of the String,
    // but can also start from a given index,
    // allowing for the locating of all instances of the character or String.
    // It Returns: The index of val within the String, or -1 if not found.

    // We can use this to check if our event name contains the
    // id of this device

    String deviceID = System.deviceID();

    // device id = 0123456789abcdef
    // event = "diot/2019/paired/0123456789abcdef"

    if( eventName.indexOf( deviceID ) != -1 ){
      // if we get anything other than -1
      // the event came from this device.
      // so stop doing stuff

    // otherwise do your stuff to respond to
    // the paired device here

    shouldActivate = true;
    if( shouldActivate ){
        doSolenoid(  );
        shouldActivate = false;



void doSolenoid(  ){
    digitalWrite(solPin, HIGH);
    delay( 5000 ) ;
    digitalWrite(solPin, LOW);
    delay( 100 );
Click to Expand

Content Rating

Is this a good/useful/informative piece of content to include in the project? Have your say!