Metadata

Set and receive metadata values

Metadata is a key:value set of data applied to every device using the same template. Unlike Datastreams, this data stays mostly unchanged, however, if you need to read/write it, here is how to do it:

Get device Metadata

The device can request the value of its own metadata from the cloud using the key (name) of Metadata.

Double-check that you have a Metadata field with a correct name configured in the Device Template.

First, you need to send a request to Blynk.Cloud

BLYNK_CONNECTED() {
  // Send requests for different metadata
  Blynk.sendInternal("meta", "get", "Serial Number");
  Blynk.sendInternal("meta", "get", "Device Model");
  
  //"Auth Token" is a reserved metadata name, if you have your own metadata
  //with that name it will override the default implementation
  //which returns device.token field
  //you can't change the value of reserved metadata field, only if you override it
  Blynk.sendInternal("meta", "get", "Auth Token");
}

Then, parse the data stored in InternalPinMETA, which a system pin to store metadata values.

BLYNK_WRITE(InternalPinMETA) {
    String field = param[0].asStr();
    if (field == "Serial Number") {
        String value = param[1].asStr();
        // Do something with Metadata value
    } else if (field == "Device Model") {
        String value = param[1].asStr();
        // Do something with Metadata value
    } else if (field == "Auth Token") {
        String value = param[1].asStr();
        // Do something with Metadata value
    }
}

Write device metadata

The device can update the value of the metadata using the metadata key (name).

For example, if your device stores Serial Number and Device Model internally, you can write these values to corresponding metadata fields.

sn_value = "123456789"       //imaginary serial number
model_value = "RX-1-2789"    // imaginary device model name

Blynk.sendInternal("meta", "set", "Serial Number", sn_value);
Blynk.sendInternal("meta", "set", "Device Model", model_value);