AN91267 Datasheet, PDF (7/62 Pages) Ramtron International Corporation – Getting Started with PSoC

Getting Started with PSoC® 4 BLE
BLE Link Establishment
To establish a BLE link between two devices—the BLE Pioneer Kit and a smartphone, for example—you need to understand
the two GAP device roles:
 GAP Peripheral: A device that advertises its presence and accepts connection from a GAP Central device. A BLE
Pioneer Kit that implements a heart-rate measurement function is an example of a GAP Peripheral device.
 GAP Central: A device that scans for advertisements from GAP Peripherals and establishes a connection with them. A
smartphone that connects to a heart-rate measurement device is an example of a GAP Central device.
After the Central device establishes a connection with the Peripheral, both devices are said to be connected over a BLE link.
On a connected BLE link, independent of the GAP role, GATT defines two roles based on the source and destination of data:
 GATT server: A GATT server is a device that contains data or state. When configured by a GATT client, it sends data to
the GATT client or modifies its local state. For example, a heart-rate measurement device is a GATT server that sends
heart-rate data to a smartphone GATT client.
 GATT client: A GATT client is a device that configures the state of a GATT server or receives data from a GATT server.
For example, a smartphone that receives heart-rate information from the heart-rate device is a GATT client.
After establishing a BLE link, the GATT client discovers all the data present on the GATT server. Once it is discovered, the
GATT client can configure and/or read/write data from the GATT server.
Figure 6 shows an example of a BLE Pioneer Kit configured in the GAP Peripheral/GATT server role that is connected to a
smartphone configured as a GAP Central/GATT client device. The GAP and GATT role configuration on each device is
defined by the application use cases or BLE Profile. For example, a device that measures heart rate should be configured as a
GAP Peripheral device with a GATT server that exposes heart-rate data, and a smartphone that reads the heart-rate
information from a heart-rate device should be configured as a GAP Central device with a GATT client.
Figure 6. BLE Application Overview
BLE
BLE
Central Peripheral
Applications
Generic Access Profile
...
( GAP )
Generic Attribute Profile ( GATT )
Stack
Lower BLE Stack Layers
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Document No. 001-91267 Rev. *D
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