Working principle of the bluetooth
Bluetooth is a radio technology that supports short-distance communication of equipment, power level CLASS1 100 meters distance and CLASS2 10 meters distance two. Can be in the mobile phone, PDA, wireless headset, notebook computers, peripherals and other devices between the wireless information exchange. Bluetooth standard is IEEE802.15, work in the 2.4GHz band, bandwidth up to 3Mb / s. Mobile phones, PDA, GPS Bluetooth, headphones, notebook built-in Bluetooth and other general CLASS2 10 m power level, industrial applications with 100 meters more Bluetooth. Bluetooth technology specifications developed by the Bluetooth SIG organization maintenance, there are Bluetooth communication products have a lot.
The master - slave relationship of Bluetooth communication
Bluetooth technology for each pair of devices between the Bluetooth communication, must be a main role, the other from the role in order to communicate, communication, must be found by the main side, initiated pairing, chain success, the two sides that Can send and receive data. In theory, a cheap bluetooth speaker can communicate with seven Bluetooth slave devices at the same time. A device with Bluetooth communication can switch between the two roles, usually working in slave mode, waiting for other master devices to connect, and when needed, convert to master mode and initiate a call to other cheap bluetooth speakers. A Bluetooth device in the main mode to initiate a call, you need to know each other's Bluetooth address, paired password and other information, pairing is complete, you can directly call.
Bluetooth call process
The Bluetooth host device initiates a call, first looking for a Bluetooth device that can be found around it, and the slave cheap bluetooth speaker needs to be in a ready state, such as a Bluetooth headset that requires keystrokes to enter a searchable state, Device to find from the end of the Bluetooth device, and from the end of the Bluetooth device to match, then need to enter the terminal device PIN code, the general cheap bluetooth speaker default: 1234 or 0000, stereo Bluetooth headphones default: 8888, there are cheap bluetooth speakers do not need to enter PIN code, such as NSP-228 Bluetooth speakers. After the pairing is complete, the slave device records the trust information of the primary end device. At this time, the master can initiate a call to the slave cheap bluetooth speaker. Depending on the application, it may be an ACL data link call or a SCO voice link call. Of the device in the next call, no longer need to re-paired. Pairing the cheap bluetooth speaker, as a slave from the Bluetooth headset can also initiate a chain request, but do not communicate with the Bluetooth module does not initiate a call. After the link is established, the master and slave can perform two-way data or voice communication between the two ends. In the communication state, the master and slave cheap bluetooth speakers can initiate a chain break and disconnect the Bluetooth link.
Bluetooth one-on-one serial data transmission applications
Bluetooth data transmission applications, one to one serial data communication is one of the most common applications, the Bluetooth device in the factory before the two Bluetooth devices in front of the match between the information, the main end of the secondary cheap bluetooth speaker from the PIN code, Address, etc., both ends of the cheap bluetooth speaker power is automatically built chain, transparent serial transmission, no external circuit intervention. One-to-one application from the end device can be set to two types, one is silent, that is, only with the designated side of the main communication, not by other Bluetooth cheap bluetooth speakers to find; Second, the development of the state, , Can also be found by other Bluetooth devices to build chain.
