Description
The BT-09 (often listed as the AT-09 or HM-10) is a Bluetooth Low Energy (BLE) 4.0 serial transceiver module. In simple terms, it’s a tiny, low-power wireless device that allows a microcontroller (like an Arduino) to communicate with a smartphone, tablet, or computer over Bluetooth. It uses the Texas Instruments CC2541 system-on-chip, which integrates a Bluetooth radio and a microcontroller core.
Key Features
- Bluetooth Version: Bluetooth 4.0 BLE (Bluetooth Low Energy) .
- Chipset: Texas Instruments CC2541 .
- Operating Voltage: Typically 3.3V to 6V, with 3.3V logic levels .
- Communication: UART serial protocol. You send and receive data through TX/RX pins using AT commands .
- Default Baud Rate: 9600 bps (configurable) .
- Low Power Consumption: Has deep-sleep modes, making it suitable for battery-powered projects
- Support Master/Slave Roles: The module can be configured as a master or a slave , giving you flexibility in your project architecture
Pinout Reference
A typical BT-09/AT-09 module has the following key pins :
| Pin | Function |
|---|---|
| VCC | Power supply (3.6V – 6V) |
| GND | Ground |
| TXD | UART Transmit (connect to MCU RX) |
| RXD | UART Receive (connect to MCU TX) |
| STATE / EN | Connection status output (HIGH when connected) / Enable pin |
Application
This module is popular in projects requiring low-power wireless communication :
- Wireless Data Transmission: Sending sensor data from an Arduino/ESP32 to a smartphone app .
- Home Automation: Creating a wireless interface for lights, switches, or plugs .
- Robotics: Using a phone app to control a robot .
- Portable Devices: Enabling communication for wearables or other battery-powered electronics