Something you need know about BLE module

Bluetooth includes classic Bluetooth and low energy Bluetooth. Bluetooth low energy is developed based on classic Bluetooth, but it is different from classic modules. It can reduce cost and power consumption. Users can quickly search and quickly connect. It stays connected and transmits data with ultra-low power consumption.

What is the principle of Bluetooth Low Energy?

1.      Bluetooth communication Master and Slave.

Bluetooth technology stipulates that for the devices in Bluetooth communication, one must be in the master role and the other in the slave role. When communicating, the master must search for and initiate pairing. After the link is established, both parties can send and receive data. In theory, a Bluetooth master device can communicate with 7 Bluetooth slave devices at the same time. A device with a Bluetooth communication function can switch between the two roles. It usually works in slave mode and waits for other master devices to connect. When necessary, it switches to master mode and initiates calls to other devices. When a Bluetooth device initiates a call in master mode, it needs to know the other party's Bluetooth address, pairing password, and other information. After pairing is completed, the call can be initiated directly. This can explain why it is sometimes unable to connect to Bluetooth. It may be that there are too many Bluetooth devices connected.

2.      Bluetooth call process

When the Bluetooth master device initiates a call, the first step is to search the Bluetooth devices. After the master device finds the slave Bluetooth device, it will pair with the slave Bluetooth device. At this time, the PIN code of the slave device needs to be entered, 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 during 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 successfully established, two-way data or voice communication can be carried out between the master and the slave. In the communication state, both the master and slave devices can initiate link disconnection and disconnect the Bluetooth link.

3.      Bluetooth one-to-one serial data transmission application

The Bluetooth device sets the pairing information between the two Bluetooth devices in advance before leaving the factory. The master has pre-stored the PIN code of the slave device, MAC Address, etc., when the devices at both ends are powered on, the link is automatically established, and the serial port is transparently transmitted without the intervention of peripheral circuits. In one-to-one applications, the slave device can be set into 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 second is the development state, which can be searched by the designated master. It can also be searched and established by other Bluetooth devices.