“Bluetooth, a familiar word. In modern life, the use of many devices is inseparable from the help of Bluetooth. Usually, what we use more is to use Bluetooth to connect headphones and mobile phones. However, do you know the specific concept of Bluetooth? Do you know the transmission principle of Bluetooth? If you are not very familiar with these issues, or you are interested in the transmission principle of Bluetooth, you may wish to read this article with the editor.

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Bluetooth, a familiar word. In modern life, the use of many devices is inseparable from the help of Bluetooth. Usually, what we use more is to use Bluetooth to connect headphones and mobile phones. However, do you know the specific concept of Bluetooth? Do you know the transmission principle of Bluetooth? If you are not very familiar with these issues, or you are interested in the transmission principle of Bluetooth, you may wish to read this article with the editor.

First, the concept of Bluetooth

Bluetooth (Bluetooth) was initially formulated by five manufacturers including Ericsson, Nokia, IBM, Intel, and Toshiba. It is a communication interface for short-distance wireless transmission. The basic communication distance is about 10 meters, and the transmission rate is about 721kbps. It works at 2.4GHz. On the frequency band, it supports one-to-many data transmission and voice communication. Since Bluetooth was not designed to carry heavy traffic loads, it is not a suitable replacement for a LAN or WAN. As the name suggests, a Bluetooth headset is a headset with the above-mentioned Bluetooth function, which is now mostly used to communicate with a mobile phone with Bluetooth function.

Bluetooth technology is an open global specification for wireless data and voice communication. It is a special short-range wireless technology connection that establishes a communication environment for fixed and mobile devices based on low-cost short-range wireless connections.

Second, the role of Bluetooth

Bluetooth enables some of today’s portable mobile and computer devices to connect to the Internet without cables, and to access the Internet wirelessly.

Third, the principle of Bluetooth transmission

1. Master-slave relationship:

Bluetooth technology stipulates that when Bluetooth communication is performed between each pair of devices, one must be the master role and the other must be the slave role to communicate. During communication, the master must search and initiate pairing. After the link is successfully established, both parties will be Data can be sent and received. In theory, a Bluetooth master device can communicate with 7 Bluetooth slave devices at the same time. A device with Bluetooth communication function can switch between two roles. It usually works in slave mode, waiting for other master devices to connect. When needed, it switches to master mode and initiates calls to other devices. When a Bluetooth device initiates a call in the master mode, it needs to know the other party’s Bluetooth address, pairing password and other information. After the pairing is completed, it can directly initiate a call.

2. Call process:

When the Bluetooth master device initiates a call, the first step is to search to find out the Bluetooth devices that can be searched around. After the master device finds the slave Bluetooth device, it pairs with the slave Bluetooth device. At this time, it needs to enter the PIN code of the slave device, and some devices do not need to enter the PIN code.

After the pairing is completed, the slave Bluetooth device will record the trust information of the master device. At this time, the master can initiate a call to the slave device, and the paired device does not need to be paired again for the next call. The paired device, as the slave Bluetooth headset, can also initiate a link establishment request, but the Bluetooth module for data communication generally does not initiate a call.

After the link is established successfully, two-way data or voice communication can be carried out between the master and slave ends. In the communication state, both the master and slave devices can initiate disconnection and disconnect the Bluetooth link.

3. Data transmission

In the Bluetooth data transmission application, one-to-one serial data communication is one of the most common applications. The Bluetooth device has set the pairing information between the two Bluetooth devices in advance before leaving the factory. Addresses, etc., when the devices at both ends are powered on, the chain is automatically established, and the transparent serial port transmission does not require the intervention of peripheral circuits.

In the one-to-one application, the slave device can be set to two types, one is the silent state, that is, it can only communicate with the designated master and cannot be searched by other Bluetooth devices; the other is the development state, which can be searched by the designated master. , and can also be found by other Bluetooth devices to establish a link.