How to establish a connection between Bluetooth devices __bluetooth

The following definitions come from bluetooth.org

connectable Device:

A Bluetooth device in range this periodically listens on its page scan physical channel and'll respond to a page on Channel

Discoverable Device:

A Bluetooth device in range this periodically listens on A Inquiry scan physical channel and would respond to A inquiry O n that channel. Discoverable device are normally
Also connectable.

Paging Device:

A Bluetooth device is carrying the page procedure.

Inquiry:

A procedure where a Bluetooth device transmits inquiry messages and listens for responses in order to discover the other B Luetooth devices that are within the coverage area

Inquiry Scan:

A procedure where a Bluetooth device listens for inquiry messages received on its inquiry scan physical channel

Page:

The initial phase of the connection procedure where a device transmits a train of page messages until a response is Receiv Ed from the target device or a timeout occurs.

Page Scan:

A procedure where a device listens for page messages received on its page scan physical.

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The following is transferred from http://blog.163.com/hancker_31/blog/static/3558736120114651834842/

How to establish a connection between Bluetooth devices

2011-05-06 17:18:34|  Category: Bluetooth | Tags: bluetooth | big size Small Subscribe

First understand a few concepts: page, page Scan; Inquiry, Inquiry Scan.
Page: Paging
Page Scan: Paging scan
Page refers to the device that initiates the connection (the primary device) knows the address to which the device is to be connected. So it can be paged directly. (Think about the pager, you know the number.)
Page scan refers to the device being in the state of waiting for paging. Usually refers to and the page pair should be from the device (wait for the connected device).

Inquiry: Query (Call)
Inquiry Scan: Query (call) scan
Inquiry, is not aware of any equipment around, to go to inquire (survey), similar to the radio (yell). Devices that are in inquiry scan can respond to this query. After the necessary consultations, they can be connected.
After Ps:inquiry, you can connect to the device without having to enter the page.

Please refer to the excerpt article:
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For Bluetooth wireless access process controller is mainly divided into standby and connection two major states. In these two states are divided into paging (page), Paging scan (page Scan), call (Inquiry), and Inquiry Scan, and the four states; In addition, paging under the host response (Master Response) child-like, The paging scan has a server response (Slave Response) Sub state, and a call-response (Inquiry Response) Sub state is consulted. As shown in Figure 1, the Bluetooth component can leave the standby state and enter the page, page Scan, inquiry, or Inquiry_scan state, and then enter the connection state. In a Bluetooth piconet, Master uses page or inquiry to establish a link with slave. If Master does not know the address of the slave component to be connected, it begins to inquiry the program to find the slave component address and its clock in piconet, but if Master is aware of the slave component address to connect to, open the page program to find the other slave.



--The procedures for wireless access, connection mode and access control are described in the following sections.

Second, access (access) program

-When you start to establish a connected wireless link, master needs to know the slave Bluetooth component address. So when the Master Bluetooth component is in the inquiry state, it uses inquiry information to indicate which Bluetooth components need to respond to inquiry and collect all the Bluetooth component addresses and clocks that respond to slave. The Master Bluetooth component in the inquiry state continues to transmit inquiry information at different FH frequencies to find other slave bluetooth components.

-and once the slave Bluetooth component is found, it is regularly entered in the inquiry scan State to respond to inquiry information. The receiver uses a matching correlator (Matching correlator) to search for inquiry access codes (access code). This search time will continue to range from 16 FH frequencies. If an active (wake-up) Slave Bluetooth component can identify Inquiry information, it enters the Inquiry response state. The Bluetooth component in the standby state can use all of its resources to search for other inquiry access Code, while the Bluetooth component in the connection state will be able to connect its existing data link to a time-saving mode to search for other inquiry access Code. The above inquiry scan programs may be interrupted by the SCO session reserved.

-When the device Access Code (DAC) is known to connect to slave, Master opens the page program to look for the slave. In the page program, master repeats a different FH frequency to transmit the slave DAC to try the connection (see Figure 2). The steps for the page program are as follows.



--First, the FH frequency sequence of the page signal is determined by the slave DAC.

--master predicts the wake-up time and FH frequency of slave with the predicted slave clock.

--in each transfer period, master sequentially launches two different frequencies.

In each successive receiving period, the slave receiver, based on the hop frequency used by page scan, detects the two corresponding receiving frequencies sequentially.

The--page program may be interrupted by the SCO session reserved. When the slave component succeeds in receiving master page information, master and slave start a routine response to exchange information. The successful connection between master and slave is to use the same frequency access code that is exported by the Bluetooth component address (BD_ADDR) and the same FH frequency, and master and slave clocks need to be synchronized.

--The following describes the steps in the response State program.

--1.slave Response Status:

--(1) Slave after receiving the DAC from master, the FH frequency used by page response responds to this DAC as confirmation.

-(2) After transmitting the response information, the slave receiver opens and waits for the FH Sync (FHS) packet from master.

--(3) If slave correctly received this FHS packet, slave the FH frequency used in page response back to its DAC for confirmation.

--(4) slave can be FHS from the contents of the packet to learn the difference between the slave clock and master clock.

--(5) Slave after correcting this clock difference, can enter the connection state.

--(6) If slave before entering the connection state, the above steps to establish the connection fail, then slave back to page scan state.

-After entering the connection state, a poll packet is sent by master first. If slave has not successfully received this poll packet, master and slave will respectively return to page and page scan status.

--2.master Response State

--(1) master, after receiving the response information returned by slave, fixed its existing clock and entered it into the page FH frequency selection scheme.

-(2) master uses this selected page FH frequency to transmit FHS packets. This FHS packet contains all the information required to construct the channel access code.

--(3) after the master transmission FHS Packet, that is, waiting for slave confirmation.

--(4) if not received slave confirmation, Master will be updated with the clock to send FHS packet.

-(5) If a slave is received, Master enters the connection state and uses BD_ADDR to exchange the FH sequences used with the slave.

--(6) After entering the connection state, Master begins to transmit a poll packet.

Three, connection mode

-In the connection state, the slave component can stay in active, Sniff, Hold, and Park 4 modes. The following are explained separately.

--1.active mode

--(1) The Active slave detects that there are no packets during the time period when master is transmitting to slave.

--(2) in order to maintain the synchronization between master and slave, even if no information is needed for transmission, master also needs to periodically transmit packets to slave.

--(3) If an active slave is not addressed by master, it sleeps until the next new master-pass-slave period.

--(4) Active slave can export the number of time periods that master is scheduled to transmit to slave.

--2.sniff mode

-(1) in this energy-saving mode, the slave can reduce the task time (dutycycle) of the activity of reconnaissance (master transfer to slave period).

--(2) master may issue a sniff instruction via the link Management (LM) protocol. This sniff instruction contains the difference between the length of the sniff and the start clock.

--(3) If slave is using an ACL link connection, the slave component must detect the period of time each master passes to slave.

--3.hoid mode

-(1) Slave with ACL links can be placed in hold mode.

-(2) The slave that operates in this hold mode still retains its active Member component address (AM_ADDR).

-(3) in this mode, slave does not provide ACL link services, but it still provides SCO link services.

-(4) thus releasing the energy to allow slave to paging inquiring or join another piconet.

--4.park mode

--(1) The slave operating in park mode is still in sync with master.

-(2) in this mode, slave has abandoned its am_addr and accepted a Park member component address (PM_ADDR) and an Access Request component address (AR_ADDR).

-(3) in a piconet, park's save will wake up after a regular period of time to keep in sync with master.

-(4) park's slave regular wake up activity will query whether there is broadcast information in the boot (Beacon) channel used by master.

-The Beacon channel in the above park mode is composed of a periodically transmitted beacon period or a column of periodically transmitted and equidistant beacon periods, as shown in Figure 3. The parameters, such as the period and the number of periods, are transmitted from master to slave in park mode by LM Protocol instruction. The Beacon Channel has the following purpose: Via Beacon Channel, master can transmit slave and the packets needed to synchronize with the Beacon channel can load the information needed to change the beacon time parameters; The Beacon channel can carry the broadcast information of master; Master can use the Beacon channel to reactivate the slave in park mode.