Events

This tutorial will help you with creating Events in Device Templates

Events are used to track, log, and work with important events that happen on the device.

Events are also used for notifications which can be sent over email, delivered as push notifications to the user's smartphone, or sent as an SMS.

Events are pre-configured in Blynk.Console and can be triggered with a Events Firmware API from the device or using Events HTTP API.

Examples of an Event:

• Log a moment when a temperature reaches a certain threshold and send a notification to selected users

• Track the total working hours of the device. If it approaches or goes beyond a maximum value, you would need to notify technical support so that they can replace the device or provide warranty service

Events list in the template

Types of Events

There are three types of Events in Blynk:

• System Events: Default Blynk platform events, like "OTA Update"

• Custom Events: Events you can create and configure for your needs

• Content Events: Informative events that are shown separately in the app

System Events

You can't delete the system events or edit them.

Firmware Over-The-Air Update status

This is a system event to track firmware updates. It can't be configured.

Custom Events

These are Events you can configure based on what your device does. Read these articles to start logging events and sending notifications:

• Event Settings

• How to send custom events from hardware using Firmware API and HTTPS API

• Content Events

How to log an event in Blynk

1. Create a Template or use an existing one

2. Create a New Event

Go to Developer Zone -> My Templates -> Select a template -> Open the "Events & Notifications" tab.

1. Click Edit Template

2. Click + Create Event

3. Name the first event with the name Hello

4. Click Create (the event will appear in the Events tab list)

5. Repeat the previous step for the second event with the name Error

6. Click Save to save and apply the changes made (select Update active device this time)

Note that each event hasEVENT_CODE. This event code will be used in firmware API or HTTPS API

Send Events Using Firmware API

1. Create a new Event named High temperature with code high_temp

2. Use the Blynk.logEvent(event_code) firmware API command to trigger a new event:

if (temperature > 35)
{
   Blynk.logEvent("high_temp");
}

When this code works, an Event will be logged and the system will act accordingly to the Event setup (render on the timeline, send notifications, etc.)

Don't log an event too many times to avoid hitting daily limits. You can use timers or flags to mark the already-sent events. Check this article on how to avoid spamming the server with events

The current limit is 100 events per device per day. This limit could be increased for business clients to fit their needs.

Custom Event Description

You can change the description of the event when it's rendered on the timeline in Blynk.Console and in Blynk.Apps. For example, you can include the current data

if (temperature > 35)
{
  Blynk.logEvent("event_code", String("High TemperatureDetected! Tº: ") + temp);
}

Make sure you enabled Timeline recording in the Event Settings to see the result in the apps

Send Events Using HTTPS API

To log an event via GET request:

`/external/api/logEvent?token={AuthToken}&code={event_code}

To add a custom description to the event, use this GET request

`/external/api/logEvent?token={AuthToken}&code={event_code}&description={event_description}

Example:

https://blynk.cloud/external/api/logEvent?token=GVki9IC70vb3IqvsV0YD3el4y0OpneL1&code=firmware_update&description=test

3. Sending Events

You can test the Event creation by sending it from Device using Blynk.Edgent firmware API, or with REST API.

Use Blynk.logEvent() firmware API

Blynk.logEvent("event_code", "optional message");

For this tutorial, you would need to use hello as a name. Here is a pseudo-code:

if (some_condition){
    Blynk.logEvent("hello");
}

Optionally, you can send a custom description of the event. This description will be rendered on Device Timeline.

if (some_condition){
    Blynk.logEvent("hello", "Hello World,") ;
}

Use HTTP REST API

1. Navigate to the Device

2. Click on its name

3. Open the Device Info tab

4. Find Auth Token there and click on the icon to copy it to the clipboard

Device Info tab with Auth Token

Auth Token. Click copy Auth Token pictogram here

Now make an HTTP request with the tools you use for that. Make sure to change the AuthToken to the one you copied in the previous step.

You can even use your browser for that. Just put it in the URL field and press Enter.

https://blynk.cloud/external/api/logEvent?token=AuthToken&code=hello

Repeat the same with code=error

https://blynk.cloud/external/api/logEvent?token=AuthToken&code=error

4. Checking if the Event was logged

First of all, check Device Timeline by going to Device -> Timeline tab

Device Timeline tab

You should see 2 events on the timeline! If you set up notifications, they should have been delivered as well.

Limitations

• You can send only 100 events per device per day (Adjustable in Business Plan)

• When the limit is reached you'll see the notification on the UI in the Device Timeline section

• The maximum description length for the event is 300 characters