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3 years ago.

GattCharacteristic maximum size?

In the Advanced Samples section on BLE docs, High Data Rate Low Latency Transfers (https://docs.mbed.com/docs/ble-intros/en/latest/AdvSamples/HighData/#often)...it is said that a characteristic with larger data bytes can be declared as follows:

WriteOnlyArrayGattCharacteristic<uint8_t, NUM_BYTES> writeTo(uuid, valuePtr,
        GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_WRITE_WITHOUT_RESPONSE);

My question is that what is the maximum NUM_BYTES that can be used? As in, what is the maximum size of data that can be encapsulated in a characteristic?

Question relating to:

Bluetooth Low Energy (a.k.a Bluetooth LE, BTLE, Bluetooth Smart)
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1 Answer

3 years ago.

Hi Anas,

I believe the Bluetooth specification states that the maximum size of an attribute is 512 bytes; therefore, since a Characteristic is basically a collection of attributes, that would be the maximum size of your data attribute.

This is the specification: https://www.bluetooth.org/DocMan/handlers/DownloadDoc.ashx?doc_id=286439 Have a look at section 3.2.9.

Thanks!

posted by Anas Imtiaz 02 Dec 2015

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