AT-09 CC2541 Bluetooth V4.0 Serial Wireless Module User’s Guide

1. Overview

The AT-09 is a compact Bluetooth V4.0 BLE (Bluetooth Low Energy) module based on the TI CC2541 chip. It’s commonly used for wireless serial communication between microcontrollers (Arduino, ESP32, STM32, etc.) and smartphones or PCs.

• Bluetooth Version: 4.0 BLE
• Chipset: TI CC2541
• Communication: UART (serial)
• Default Baud Rate: 9600 bps (configurable)
• Range: ~10–20 meters (depending on environment)
• Supply Voltage: 3.6V – 6V (recommended 5V input, 3.3V logic)

2. Pinout

3. Setup & Wiring

Step 1: Power

• Connect VCC to 5V (or 3.3V if using low-voltage systems).
• Connect GND to ground.

Step 2: Serial Connection

• Connect TXD → RX of microcontroller.
• Connect RXD → TX of microcontroller.
• Use a voltage divider if your MCU TX is 5V (module expects 3.3V logic).

Step 3: Status Pin (Optional)

• Connect STATE pin to an LED or MCU input to monitor connection status.

4. Configuration

• The module can be configured using AT commands over UART.
• Enter AT mode by powering the module and sending commands at the correct baud rate (default: 9600 bps, 8N1).
• Common AT commands:
  • AT → Test command (responds “OK”)
  • AT+NAME? → Query device name
  • AT+NAME=MyDevice → Set device name
  • AT+BAUD? → Query baud rate
  • AT+BAUD4 → Set baud rate to 9600

5. Applications

• Wireless Serial Communication: Replace wired UART with Bluetooth.
• Smartphone Control: Send/receive data from mobile apps (e.g., Arduino Bluetooth apps).
• IoT Projects: Remote monitoring and control of sensors.
• Robotics: Wireless control of robots or drones.

6. Safety & Best Practices

• Ensure logic level compatibility (use voltage divider for RX if MCU is 5V).
• Keep module away from strong RF interference.
• Use proper power supply filtering (capacitors) for stable operation.
• Test AT commands before integrating into final project.

7. Troubleshooting