Events

Getting Started -> Events
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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 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 device or using Events HTTP API.
Examples of an Event:
Log a moment when a temperature reached a certain threshold and send a notification to selected users
Track total working hours of the device. If it approaches or goes beyond a max value, you would need to notify technical support so that they can replace the device or provide warranty service
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Events list in the template
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Types of Events
There are three types of Events in Blynk: 
System Events: Default Blynk platform events. 
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, but you can configure them.
Online/Offline status
This event is used to track when devices goes online and offline.
In some cases you would need to ignore offline state for a certain period of time. For example, if your device is mostly offline (or in deep sleep) and only wakes up every hour to send the data.
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Firmware Over-The-Air Update status
This is a system event to track firmware update. It can't be configured
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Custom Events
These are Events you can configure based on what your device do. Read these articles to start logging events and sending notifications: 
​Event Settings​
​How to send custom events fom hardware using Firmware API and HTTPS API 
​Content Events​
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1. Create a Template or use an existing one
2. Create a New Event
Go to Template -> Edit -> Events tab.
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1.Click Add New Event
2.Name the first event with the name Hello
3.Click Create (the event will appear in the Events tab list)
4.Repeat the previous step for the second event with the name Error
5.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 new event
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if (temperature > 35)
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{
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   Blynk.logEvent("high_temp");
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}
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When this code worked, an Event will be logged and the system will act accordingly to the Event setup (render on timeline, send notifications, etc.)
Avoid logging an event too many times not to hit 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
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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
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if (temperature > 35)
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{
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  Blynk.logEvent("event_code", String("High TemperatureDetected! Tº: ") + temp);
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}
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Make sure you enabled Timeline recording in the Event Settings to see the result in the apps
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Send Events Using HTTPS API
To log an event use GET request: 
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`/external/api/logEvent?token={AuthToken}&code={event_code}
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To add custom description to the event, use this GET request
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`/external/api/logEvent?token={AuthToken}&code={event_code}&description={event_description}
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Example:
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https://blynk.cloud/external/api/logEvent?token=GVki9IC70vb3IqvsV0YD3el4y0OpneL1&code=firmware_update&description=test
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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:
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if (some_condition){
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    Blynk.logEvent("hello");
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}
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Optionally, you can send a custom description with the event. This description will be rendered on Device Timeline.
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if (some_condition){
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    Blynk.logEvent("hello", "Hello World,") ;
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}
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Use HTTP REST API
1.Navigate to the Device
2.Click on its name
3.Open Device Info tab
4.Find Auth Token there and click on the icon to copy it to the clipboard
Device Info tab
Auth Token. Click copy pictogram here
Now make an HTTP request with the tools you use for that. Make sure to change the YourAuthToken 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.
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https://blynk.cloud/external/api/logEvent?token=YourAuthToken&code=hello
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Repeat the same with code=error
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https://blynk.cloud/external/api/logEvent?token=YourAuthToken&code=error
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4. Checking if Event was logged.
First of all, check Device Timeline by going to 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 devices 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
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