PM0237 datasheet(18/88 Pages) STMICROELECTRONICS

18 / 88 page

Bluetooth low energy technology

PM0237

18/88

DocID027104 Rev 2

A connection event is the time between the start of the last connection event and the

beginning of the next connection event.

A BLE slave device can only be connected to one BLE master device, but a BLE master

device can be connected to several BLE slave devices. On the Bluetooth SIG, there is no

limit on the number of slaves a master can connect to (this is limited by the specific used

BLE technology or stack).

1.4

Host controller interface (HCI)

The Host Controller Interface (HCI) layer provides a mean of communication between the

host and controller either through software API or by a hardware interface such as SPI,

UART or USB. It comes from standard Bluetooth specification, with new additional

commands for low energy-specific functions.

1.5

Logical link control and adaptation layer protocol (L2CAP)

The Logical Link Control and Adaptation Layer Protocol (L2CAP), supports higher level

protocol multiplexing, packet segmentation and reassembly operation, and the conveying of

quality of service information.

1.6

Attribute Protocol (ATT)

The Attribute Protocol (ATT) allows a device to expose certain pieces of data, known as

attributes, to another device. The device exposing attributes is referred to as the Server and

the peer device using them is called the Client.

An attribute is a data with the following components;

•

Attribute handle: it is a 16 bits value which identifies an attribute on a Server, allowing

the Client to reference the attribute in read or write requests;

•

Attribute type: it is defined by a Universally Unique Identifier (UUID) which determines

what the value means. Standard 16 bits attribute UUIDs are defined by Bluetooth SIG;

•

Attribute value: a (0 ~ 512) octets in length;

•

Attribute permissions: they are defined by each higher layer that uses the attribute.

They specify the security level required for read and/or write access, as well as

notification and/or indication. The permissions are not discoverable using the attribute

protocol. There are different permissions types:

–

Access permissions: they determine which types of requests can be performed on

an attribute (readable, writable, readable and writable)

–

Authentication permissions: they determine if attributes require authentication or

not. If an authentication error is raised, client can try to authenticate it by using the

Security Manager and send back the request.

–

Authorization permissions (no authorization, authorization): this is a property of a

server which can authorize a client to access or not to a set of attributes (client

cannot resolve an authorization error).

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