Hardware Reference
In-Depth Information
Table 4-5. Characteristic declaration attribute value
Name
Length in bytes
Description
Characteristic Properties
1
A bitfield listing the permitted operations on this characteristic
Characteristic Value Handle
2
The handle of the attribute containing the characteristic value
Characteristic UUID
2, 4, or 16
The UUID for this particular characteristic
These three fields are contained in a characteristic declaration attribute value:
Characteristic Properties
This 8-bit bitfield, along with the additional two bits in the extended properties
descriptor (discussed in
“Extended Properties Descriptor” on page 62
), contains the
operations and procedures that can be used with this characteristic. Each of those
10 properties is encoded as a single bit on the bitfield shown in
Table 4-6
.
Table 4-6. Characteristic properties
Property
Location
Description
Broadcast
Properties
If set, allows this characteristic value to be placed in advertising packets, using the Service
Data AD Type (see
“GATT Attribute Data in Advertising Packets”
)
Read
Properties
If set, allows clients to read this characteristic using any of the ATT read operations listed
in
“ATT operations”
Write without
response
Properties
If set, allows clients to use the Write Command ATT operation on this characteristic (see
“ATT operations”
)
Write
Properties
If set, allows clients to use the Write Request/Response ATT operation on this characteristic
(see
“ATT operations”
)
Notify
Properties
If set, allows the server to use the Handle Value Notification ATT operation on this
characteristic (see
“ATT operations”
)
Indicate
Properties
If set, allows the server to use the Handle Value Indication/Confirmation ATT operation on
this characteristic (see
“ATT operations”
)
Signed Write
Command
Properties
If set, allows clients to use the Signed Write Command ATT operation on this characteristic
(see
“ATT operations”
)
Queued Write
Extended
Properties
If set, allows clients to use the Queued Writes ATT operations on this characteristic (see
“ATT operations”
)
Writable
Auxiliaries
Extended
Properties
If set, a client can write to the descriptor described in
“Characteristic User Description
Descriptor”
The client can read those properties to find out which operations it is allowed to perform
on the characteristic. This is particularly important for the Notify and Indicate prop‐
erties, because these operations are initiated by the server (further detailed in
“Server-
Initiated Updates” on page 72
) but require the client to enable them first by using the
descriptor described in
“Client Characteristic Configuration Descriptor” on page 62
.
