Bluetooth configuration files and Protocols (General)

Starting from this article, we will introduce some Bluetooth profiles and protocol as an entry-level reader. For details, refer:

Bluetooth SIG

Bluetooth Wiki

The instructions on how to use Bluetooth devices are handed over to the above-mentioned websites. This site is committed to clarifying the technical specifications of protocols and profiles.

First, the architecture of the Bluetooth protocol layer is described in this document.

Host and Controller

Shows the stack structure of the protocol layer.
Although the main structure is shown here, there are some parts that have not yet been shown.

The part marked as controller corresponds to the part of the Bluetooth chip.
The USB adapter used on a PC belongs to this controller.

The host part is loaded with software that can control the controller.
If you compare the USB adapter on the PC, the host is the part of the PC.

For scenarios such as headset and mouse, hardware products that provide a single chip (including host and controller) are mainly used.
In order to achieve miniaturization and reduce costs, we also sell a chip named hid configuration file, which is dedicated to the MK/HFP configuration file.

HCI (host contoroller Interface)

This article only discusses the host part above the controller, so we will start with HCI.

HCI is a protocol for communication between the Controller and the host.
Unlike other protocols for communication with the other device, only HCI is used for internal communication.
The command used to transmit data from the host to the Controller, and the event used to transmit data from the Controller to the host. The data transfer between the two is like this through packet) communication completed.

The HCI protocol communicates through a physical bus named uart and USB.
These physical buses communicate with each other through various protocols, so HCI actually communicates with each other over these protocols.
For a single-chip product, including a configuration file, it is generally considered that its HCI part is communicated through software.

L2CAP (Logical Link Control and Adaptation Protocol)

L2CAP is a protocol used to manage multiple links.
In addition to managing the links of multiple devices, you can also manage the links of the same device.
The management of several links of the same device means that, for example, a channel used for SDP communication and a channel used for RFCOMM communication are opened at the same time, these channels are managed to distinguish them from each other without mutual interference.

SDP (Service Discovery Protocol)

Using Bluetooth technology, you can enjoy a variety of services, such as headset, hands-free phone, dial-up, input devices, image transmission, music transmission, and so on.
However, this does not mean that all devices can support all services.
SDP is the protocol used to search for the services supported by the other device.

RFCOMM

RFCOMM is a protocol that simulates RS232 serial communication.
It provides signal transmission for each pin of RS232 and Management of the plural port.

Many configuration files use the RFCOMM protocol.
These configuration files include spp (Serial Port profile), DNP (dial-up networking profile), MK (headset profile), HFP (hands free profile), lap (LAN Access Profile ), some configuration files that use the OBEX protocol, including object push profile (OPP.

Obex (Object Exchange Protocol)

Obex is a protocol used for Object Exchange, which is also used for infrared communication.
Using obex to transmit HTTP strings in binary mode reduces the amount of communication, making it feel like a wireless version of HTTP.
OPP (Object push profile), sync (Synchronization Profile), FTP (file transfer profile), bip (basic imaging profile) and other configuration files use this protocol.

Profile)

The profile is not a protocol. It determines how to provide/use the corresponding services.

Although the same configuration file cannot be supported, communication is not allowed. However, because the configuration file contains two different roles: the provider and the user, so it is also necessary to pay attention.
For example, in the case of dial-up Internet access, one side is the gateway side (that is, the provider of the dial-up Internet Service) in the dial-up networking profile ), if the other party does not support the data terminal side (that is, the user of the dial-up Internet Service), it cannot communicate.

In addition, the configuration file contains the default function and option function, and the configuration file may not support the option function.
For example, although object push profile is supported, file push (push) transmission as the option function may not be supported.

Several Representative configuration files are listed below.

Generic Access Profile (GAP)

Provides device retrieval and security services as basic functions of Bluetooth devices.

Service Discovery Application Profile

Which services can be retrieved for the other device?

Serial Port profile (SPP)

Makes the serial communication of RS232 wireless.

Dial-up networking profile (DNP)

Dial-up connection

LAN Access Profile (LAP)

Establish a LAN connection with the other device

Fax Profile

Use the fax service wirelessly

Generic Object Exchange profile (goep)

This configuration file is not used as an individual, but defines the common content of Object Exchange configuration files such as object push profile using the OBEX protocol.

Object push profile (OPP)

Provides push transmission services for objects such as business cards, calendars, and files, as well as business cards.

File Transfer profile (FTP)

Send and receive files

Synchronization Profile (Sync)

Process files similar to PDA and PC content during the same period

Headset profile (MK)

Use a headset for voice calls

Hands Free profile (HFP)

Added the phone call function to headset profile.

Human Interface Device profile (HID)

Wireless communication between the mouse, keyboard, and other input devices

Basic imaging profile (BIP)

Send and receive images

Hardcopy cable replacement profile (HCRP)

Replacement of printed cables in wireless mode

Basic printing profile (BPP)

Provides simple printing services without a printer driver

Personal area network profile (PAN)

Provides services to build networks for several Bluetooth devices

Advanced Audio distribution profile (a2dp)

Provide music transmission service

Audio/Video remote control profile (avrcp)

Provides the Control Service (Remote Control) When transmitting audio and video content)

In addition to the types listed here, there are other configuration files available for use.

Other protocols

The Protocol described above is used in most configuration files as a representative type of common.
In addition, there are also dedicated protocols for configuration files.
For example, the so-called avdtp (audio/video distribution Transport Protocol) in a2dp and the so-called avdio/video control transport protocol in avrcp.

(Where, big content reference: http://article.yeeyan.org/view/jianermei/49981)