AN91267 Datasheet, PDF (57/62 Pages) Ramtron International Corporation – Getting Started with PSoC

Getting Started with PSoC® 4 BLE
Figure 67 shows the data hierarchy using Attributes, Characteristics, Services, and Profiles defined previously in this
section.
Figure 67. BLE Data Hierarchy*
* Image courtesy of Bluetooth SIG
Attribute Operations
Attributes defined in the previous section are accessed using the following five basic methods:
 Read Request: The GATT client sends this request to the GATT server to read an Attribute value. For every
request, the GATT server sends a response to the GATT client. A smartphone reading the Battery-Level
Characteristic of a heart-rate monitor device (see Figure 65) is an example of a Read Request.
 Write Request: The GATT client sends this request to the GATT server to write an Attribute value. The
GATT server responds to the GATT client, indicating whether the value was written. A smartphone writing a
value of 0x01 to the CCCD of a Battery Level Characteristic to enable notifications is an example of a Write
Request.
 Write Command: The GATT client sends this command to the GATT server to write an Attribute value. The
GATT server does not send any response to this command. For example, the BLE Immediate Alert Service
(IAS) uses a Write Command to trigger an alert (turn on an LED, ring a buzzer, drive a vibration motor, and so
on) on an IAS Target device (for example, a BLE key fob) from an IAS locator (for example, a smartphone).
 Notification: The GATT server sends this to the GATT client to notify it of a new value for an Attribute. The
GATT client does not send any confirmation for a notification. For example, a heart-rate monitor device sends
heart-rate measurement notifications to a smartphone when its CCCD is written with a value of 0x01.
 Indication: The GATT server sends this type of message. The GATT client always confirms it. For example,
a BLE Health Thermometer Service (HTS) uses indications to reliably send the measured temperature value
to a health thermometer collector, such as a smartphone.
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Document No. 001-91267 Rev. *D
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