BLE GATT API

1.2

Date:
2013-09-05 11:19:58 -0700 (Thu, 05 Sep 2013)
Revision:
35219

Description: This file contains Generic Attribute Profile (GATT) definitions and prototypes.

HighLevelGATT.PNG
 Functional Description

Functional Description

The Generic Attribute Profile (GATT) defines a service framework using the Attribute Protocol (ATT). This framework defines procedures and formats of services along with their characteristics. These procedures include discovering, reading, writing, notifying and indicating characteristics, as well as configuring the broadcast of characteristics on a peer device.

 

Configurations and Roles

The GATT Profile defines the following two roles for devices:

·          Client - This is the device that initiates commands and requests towards the server and can receive responses, indications and notifications sent by the server.

·          Server - This is the device that accepts incoming commands and requests from the client and sends responses, indications and notifications to a client.

These roles are not fixed to the device. The roles are determined when a device initiates a procedure, and released when the procedure ends. Hence, a device can act in both roles simultaneously.

 

Profile Hierarchy

The GATT Profile specifies the structure in which data provided by a profile is exchanged. This structure defines basic elements, such as services and characteristics, used in a profile. These elements are all contained by Attributes, which are containers that carry the profile data.

The top level of the hierarchy is a profile. A profile is composed of one or more services needed to fulfill a use case. A service is composed of characteristics or references to other services. Each characteristic contains a value and may contain optional information about the value. The service and characteristic and the components of the characteristic (i.e. value and descriptors) contain the profile data and are all stored in Attributes on the server.

 

Defined Features

The GATT Profile defines a total of 11 features. Each feature is mapped to procedures and sub-procedures. These procedures and sub-procedures describe how the ATT is used to accomplish the corresponding feature:

·          Server Configuration - This procedure is used by the client to configure the ATT. This procedure has only one sub-procedure used to set the MTU sizes: Exchange MTU.

·          Primary Service Discovery - This procedure is used by a client to discover primary services on a server. There are two sub-procedures that can be used for primary service discovery: Discover All Primary Services and Discover Primary Services by Service UUID.

·          Relationship Discovery - This procedure is used by a client to discover service relationships to other services. There is one sub-procedure that can be used for relationship discovery: Find Included Services.

·          Characteristic Discovery - This procedure is used by a client to discover service characteristics on a server. There are two sub-procedures that can be used for characteristic discovery: Discover All Characteristics of a Service and Discover Characteristics by UUID.

·          Characteristic Descriptor Discovery - This procedure is used by a client to discover characteristic descriptors of a characteristic. There is one sub-procedure that can be used for characteristic descriptor discovery: Discover All Characteristic Descriptors.

·          Reading a Characteristic Value - This procedure is used to read a Characteristic Value from a server. There are four sub-procedures that can be used to read a Characteristic Value: Read Characteristic Value, Read Using Characteristic UUID, Read Long Characteristic Values, and Read Multiple Characteristic Values.

·          Writing a Characteristic Value - This procedure is used to write a Characteristic Value to a server. There are five sub-procedures that can be used to write a Characteristic Value: Write Without Response, Signed Write Without Response, Write Characteristic Value, Write Long Characteristic Values and Reliable Writes.

·          Notification of a Characteristic Value - This procedure is used to notify a client of the value of a Characteristic Value from a server. There is one sub-procedure that can be used to notify a value: Notification.

·          Indication of a Characteristic Value - This procedure is used to indicate the Characteristic Value from a server to a client. There is one sub-procedure that can be used to indicate a value: Indication.

·          Reading a Characteristic Descriptor - This procedure is used to read characteristic descriptors on a server. There are two sub-procedures that can be used to read characteristic descriptors: Read Characteristic Descriptors and Read Long Characteristic Descriptors.

·          Writing a Characteristic Descriptor - This procedure is used to write characteristic descriptors on a server. There are sub-procedures that can be used to write characteristic descriptors: Write Characteristic Descriptors and Write Long Characteristic Descriptors.

 

 

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