What does CCCD mean?

[Sébastien Despont]

Dear Nordic Developer Zone,

I have a silly question. After searching in the Nordic and Bluetooth documentation, I didn't find what CCCD and SCCD mean. Theses metadata are parts of the characteristics.

Can you explain me what these acronyms mean? And wher I could find any documentation about it?

Best regards

[Ole Morten]

CCCD is an abbreviation for Client Characteristic Configuration Descriptor. This descriptor is defined in the Core Specification, Volume 3, Part G, section 3.3.3.3.

This descriptor will be added automatically by the S110 softdevice for any characteristic that has either the Notify or the Indicate properties. In your characteristic setup you will however have to set up the metadata you want for this descriptor, for example which security level is required to write it.

The use of it is for a GATT Client to control what kind of packets the GATT Server can send to it. As you may know, there are some so-called server initiated properties, Notifications and Indications (part F, 3.4.7). A Server can only send such packets to the Client if the Client have written either 1 (to enable notifications) or 2 (to enable indications) to the CCCD for the characteristic in question.