Hardware Reference
In-Depth Information
ture present in ATT, but the data is now encapsulated in
services
, which consist of one
or more
characteristics
. Each characteristic can be thought of as the union of a piece of
user data along with
metadata
(descriptive information about that value such as prop‐
erties, user-visible name, units, and more).
Chapter 4
discusses GATT in much more detail. Along with GAP, GATT is an upper-
layer entity that acts as the main interface to a Bluetooth Low Energy protocol stack.
Generic Access Profile (GAP)
The Generic Access Profile (GAP) dictates how devices interact with each other at a
lower level, outside of the actual protocol stack. GAP can be considered to define the
BLE topmost control layer, given that it specifies how devices perform control proce‐
dures such as device discovery, connection, security establishment, and others to ensure
interoperability and to allow data exchange to take place between devices from different
vendors.
GAP establishes different sets of rules and concepts to regulate and standardize the low-
level operation of devices:
• Roles and interaction between them
• Operational modes and transitions across those
• Operational procedures to achieve consistent and interoperable communication
• Security aspects, including security modes and procedures
• Additional data formats for nonprotocol data
Chapter 3
discusses GAP in more detail.
