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Bluetooth Protocol (Part 2): Types, Data Exchange, Security

Written By: 

Bijal Parikh

Host Controller Interface

HOST CONTROLLER INTERFACE

The HCI is a command interface to baseband, link manager and access to hardware status and control registers. This interface provides a uniform method of accessing Bluetooth baseband capabilities.

LOGICAL LINK AND ADAPTATION LAYER

The Logical Link Control and Adaptation Protocol (L2CAP) accept data from the higher layers of Bluetooth stack and from applications and sends it over the lower layers. It passes packets either to the Host Controller Interface (HCI), or in a host-less system, L2CAP passes packets directly to the Link Manager. These are some functions performed by L2CAP.

 

·        Multiplexing higher layer protocols and allowing them to share lower layer links. L2CAP uses PSM field in the L2CAP Connection Request Command. L2CAP can multiplex connection requests to upper layer protocols like Service Discovery Protocol, RFCOMM and Telephony Control.

·       Segmentation and reassembly to allow transfer of larger packets

It is used to improve efficiency by supporting a maximum transmission unit size larger than the largest baseband packet. L2CAP segments higher layer packets into chunks that can be passed on to the link manager for transmission and reassembles those chunks into L2CAP packets using information provided by HCI and packet header.

·         Group management and one way transmission to a group of other Bluetooth devices

{C}r·           Quality of service management for higher layer protocols.

{C}{·         L2CAP events and commands

L2CAP operates using events and commands which it receives or transmits from/to upper or lower layers. These events can be a connection request, a data write request or may be a disconnection request. The lower layer can tell L2CAP about the incoming connections, request and disconnections. If L2CAP of one unit needs to talk to other L2CAP then it uses some special commands called signaling commands.

Various signaling commands used in L2CAP are

CODE

DESCRIPTION

0*00

RESERVED

0*01

COMMAND REJECT

0*02

CONNECTION REQUEST

0*03

CONNECTION RESPONSE

0*04

CONFIGURE REQUEST

0*05

CONFIGURE RESPONSE

0*06

DISCINNECTION REQUEST

0*07

DISCONNECTION RESPONSE

0*08

ECHO REQUEST

0*09

ECHO RESPONSE

0*0a

INFORMATION REQUEST

0*0b

INFORMATION RESPONSE

Comments

which language you use for cod of microcontroler  projects

thanks

Assembly language I use for cod.

In other language we can use? Or only using assembly language

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