This service consists of a single characteristic, called Key Press State, which notifies the state changes of the buttons,
The characteristic Key Press State has a value attribute containing an unsigned integer of 8 bits.
Each bit represents the state of a button:
0is for Released
1is for Pressed
This value does not have access either read or write.
It is communicated to the client only through notifications or indications, which can be enabled via the Characteristic Client Configuration descriptor.