AN91267 Datasheet, PDF (54/62 Pages) Ramtron International Corporation – Getting Started with PSoC

Getting Started with PSoC® 4 BLE
Figure 63. BLE L2CAP Layer
APPLICATION
Connection Oriented
L2CAP Channel Command
SECURITY MANAGER (SM)
ATTRIBUTE PROTOCOL (ATT)
L2CAP
- Encryption Information
- Security Request etc.
- Read Attribute Request
- Read Attribute Response
etc.
- Connection Timing
Update
- Command Reject etc.
ATT
Commands
L2CAP Control
SM Commands
Application Data and Commands
L2CAP
Link Layer
Physical Layer
Preamble
Access Address
Header Payload
(1B) Length (1B)
Protocol Data Unit (PDU)
Payload
CRC
(x24+x10+x9+x6+x4+x3+x1+x0)
Security Manager (SM)
The SM layer defines the methods used for pairing, encryption, and key distribution.
 Pairing is the process to enable security features. In this process, two devices are authenticated, the link is
encrypted, and then the encryption keys are exchanged. This enables the secure exchange of data over the BLE
interface without being snooped on by a silent listener on the RF channel.
 Bonding is the process in which the keys and the identity information exchanged during the pairing process are
saved. After devices are bonded, they do not have to go through the pairing process again when reconnected.
BLE uses 128-bit AES for data encryption.
Attribute Protocol (ATT)
There are two GATT roles in BLE that you should know to understand the ATT and GATT layers:
 GATT server: A GATT server contains the data or information. It receives requests from a GATT client and
responds with data. For example, a heart-rate monitor GATT server contains heart-rate information; a BLE HID
keyboard GATT server contains user key press information.
 GATT client: A GATT client requests and/or receives data from a GATT server. For example, a smartphone is a
GATT client that receives heart-rate information from the heart-rate GATT server; a laptop is a GATT client that
receives key-press information from a BLE keyboard.
ATT forms the basis of BLE communication. This protocol enables the GATT client to find and access data or
Attributes on the GATT server. For more details about the GATT client and server architecture, refer to Generic
Attribute Profile (GATT).
An Attribute is the fundamental data container in the ATT/GATT layer, which consists of the following:
 ^{Attribute Handle: The 16-bit address used to address and access an Attribute.}
 ^{Attribute Type: This specifies the type of data stored in an Attribute. It is represented by a 16-bit UUID defined}
by the Bluetooth SIG.
For example, the 16-bit UUID of the Heart-Rate Service is 0x180D; the UUID for the Device Name Attribute is
0x2A00. Visit the Bluetooth web page for a list of 16-bit UUIDs assigned by the SIG.
 ^{Attribute Value: This is the actual data stored in the Attribute.}
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Document No. 001-91267 Rev. *D
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