Ⅰ.Core functions of Bluetooth UART module

 Bluetooth UART module is a wireless serial communication module that integrates Bluetooth chip and UART interface to realize wireless data transmission between devices.

Core features:

Wireless replacement of wired: converts traditional physical serial port (UART) into Bluetooth wireless communication.

Full-duplex communication: supports two-way data transmission (send and receive).

Low power consumption: most modules support sleep mode (such as BLE low-power Bluetooth).

Ⅱ. Recommended mainstream Bluetooth UART modules

1. Classic Bluetooth (BR/EDR) modules

(1) HC-05/HC-06

Core parameters:

Bluetooth version: Bluetooth 2.0 + EDR (classic Bluetooth).

Baud rate: supports 1.2–3 Mbps (configurable).

Transmit power: 2.5 dBm (HC-05) / 0 dBm (HC-06).

Protocol support: AT command configuration, support master-slave mode.

Applicable scenarios: Bluetooth debugging, serial port data transparent transmission, simple peripheral control.

2.Ebyte Bluetooth UART module recommendation:Classic Bluetooth (BT 2.1/3.0)

Model: E104-BT21

Chip: CSR BC417 (Bluetooth 2.1+EDR)

Features: Support SPP protocol (serial port transparent transmission)

Maximum transmission rate: 2Mbps (actual UART rate ≤921600bps)

Operating voltage: 3.3V, high power consumption (suitable for continuous power supply scenarios)

Application: audio transmission, high-speed data transparent transmission (such as printers)

Ⅲ. Key parameters and selection suggestions

1. Comparison of core parameters

 2. Selection Recommendations

 Low-cost prototype development: HC-05/06 (classic Bluetooth, strong compatibility).

Low power requirements: HM-10 (BLE 4.0) or HM-13 (BLE 5.0).

Long-distance transmission: Select a BLE 5.0 module (such as HM-13) and enable long-distance mode.

Ⅳ. Typical application scenarios

Wireless debugging: Connect to PC or mobile phone via Bluetooth to monitor embedded device logs in real time.

Sensor network: Transmit temperature, humidity, acceleration and other data to gateway or mobile phone via Bluetooth.

Peripheral control: Wirelessly control LED, motor and other devices (such as Bluetooth handles).

IoT gateway: Collect multiple sensor data via Bluetooth, and then upload to the cloud via Wi-Fi/4G.

Ⅴ. Common problems and solutions

 1. Unable to pair and connect

Possible reasons: Baud rate does not match, module does not enter pairing mode.

Solution:

Check whether the baud rate set by AT command AT+UART is consistent with that of the host.

Pull down the EN pin of the module to trigger pairing mode (such as HM-10 needs to send AT+BIND).

2. Data packet loss or delay

Possible reasons: Baud rate is too high, signal interference.

Solution:Reduce the baud rate (such as from 115200 to 9600).

Optimize antenna design or shorten the transmission distance.

3. Unable to enter AT command mode

 Possible reasons: The EN pin is not pulled low on time (usually triggered within 1 second after power-on).

Solution: Use hardware reset circuit or delay code to control the EN pin.

VII. Summary

The Bluetooth UART module simplifies the communication design between devices by replacing the wired serial port with wireless, which is especially suitable for applications that require rapid development, low power consumption or mobile scenarios.

Recommended models:

Low-cost solution: HC-05 (classic Bluetooth).

Low-power solution: HM-10 (BLE 4.0).

Long-distance solution: HM-13 (BLE 5.0).