Bluetooth modules have become indispensable components in IoT, smart home, and industrial automation sectors. For global buyers sourcing these modules, understanding their technical operation, compliance requirements, and application scenarios is crucial for selecting the right product and ensuring project success.
The working process of a Bluetooth module mainly involves the following aspects:
Work at the hardware layer
- Rf module:
Operates in the 2.4GHz ISM band and supports GFSK/π/4 DQPSK/8DPSK modulation modes. The transmitting end converts digital signals into radio waves, and the receiving end restores the radio waves back to digital signals, achieving wireless transmission of signals.
- Baseband controller:
It adopts Time Division duplex (TDD) mode to alternately send and receive data. It also has an adaptive frequency hopping function, randomly switching among 79 channels to avoid interference and enhance the stability and anti-interference ability of communication.
- Antenna systems:
Common types include PCB on-board antennas and ceramic antennas, etc. Antenna efficiency has a significant impact on the transmission distance of Bluetooth modules. Generally, an antenna efficiency greater than 50% can achieve a transmission distance of about 10 meters.
Protocol stack work
Controller subsystem
- Physical layer (PHY) :
It is responsible for the generation and analysis of electromagnetic wave signals, similar to a Morse code transmitter. It converts digital signals into electromagnetic wave signals for transmission and restores the received electromagnetic wave signals back to digital signals.
- Link Layer (LL) :
It is responsible for functions such as device discovery, connection management, and data packet encapsulation, just like a sorting center for express packages, processing and transmitting data.
- Host Control Interface (HCI) :
As a communication bridge between hardware and software, it is similar to the USB interface of a computer, enabling communication between the Bluetooth module and the host device.
Host subsystem
- L2CAP layer:
It mainly performs data sharding and reorganization, with a maximum support of 65,535 bytes. It also supports protocol multiplexing and can simultaneously support multiple service channels, just like disassembling large furniture into parts for transportation and reassembling them at the destination.
- ATT/GATT:
The attribute protocol defines the data storage structure, such as the storage and read-write rules for specific data like heart rate values, and identifies different data and services through specific UUids.
Working mode and process
Master device working mode:
It can search for other devices and actively establish connections, and can connect and communicate with one or more slave devices. The master device will regularly scan the broadcast information sent by the surrounding devices in broadcast mode and select the slave devices to be connected for pairing and connection. After the pairing is completed, both the master and the slave can send and receive data.
Slave device working mode:
Unconnected slave devices first enter the broadcast state, waiting to be searched by the host. When the host scans the slave device and establishes a connection, it can send and receive data with the host device. The slave device cannot establish a connection actively and can only wait for the host to connect.
Master-slave integrated working mode:
The Bluetooth module can act as both the master device and the slave device simultaneously, switching between the two roles. When working in slave mode, wait for other master devices to connect. Switch to the main mode when necessary and initiate connections to other devices.
The working mode of the broadcaster:
The Bluetooth module regularly and continuously sends broadcast data packets of a certain length to the surrounding area, and this data can be searched by the scanner. The module can continuously broadcast in a low-power mode and is applied in scenarios requiring extremely low power consumption, small data volume, and one-way transmission.
Observer working mode:
In this mode, the module is in a disconnected state and can receive data one-to-many. The device only listens to and reads the broadcast data in the air, cannot initiate a connection, and can only continuously scan the slave machine. It is often used in data acquisition concentrators and other occasions.
If you want to know more about our products, you can directly send us an email to inquire.
