How to Use Bluetooth Module AT-09: Examples, Pinouts, and Specs

The Bluetooth Module AT-09, manufactured by AD Store, is a compact and versatile Bluetooth Low Energy (BLE) module designed for wireless communication between devices. It supports BLE 4.0, making it ideal for applications requiring low power consumption and reliable data transfer. The AT-09 is widely used in IoT projects, home automation, wearable devices, and wireless sensor networks.

• Wireless data transfer between microcontrollers and smartphones
• IoT devices and smart home systems
• Remote control and monitoring applications
• Wearable technology
• Prototyping BLE-enabled devices

Below are the key technical details of the AT-09 Bluetooth module:

The AT-09 module has 6 pins, as described in the table below:

1. Power Supply: Connect the VCC pin to a 3.3V to 6V power source and the GND pin to ground.
2. UART Communication: Connect the TXD pin of the AT-09 to the RX pin of your microcontroller, and the RXD pin of the AT-09 to the TX pin of your microcontroller.
3. Enable the Module: Ensure the EN pin is HIGH to activate the module.
4. Pairing: Use a BLE-compatible device (e.g., smartphone or computer) to scan for the AT-09 module. The default name is typically "AT-09" or "HMSoft."
5. Data Transfer: Use a serial communication protocol to send and receive data between the AT-09 and the connected device.

• Voltage Levels: Ensure the microcontroller's UART pins operate at 3.3V logic levels. If using a 5V microcontroller, use a level shifter to avoid damaging the module.
• Baud Rate: The default baud rate is 9600 bps. Ensure your microcontroller's UART settings match this value.
• Range: The module's range is up to 10 meters in a clear line of sight. Obstacles and interference may reduce this range.
• Firmware Updates: The AT-09 supports firmware updates via UART. Refer to the manufacturer's documentation for update procedures.

Below is an example of how to use the AT-09 with an Arduino UNO to send and receive data:

• AT-09 VCC → Arduino 5V
• AT-09 GND → Arduino GND
• AT-09 TXD → Arduino Pin 10 (RX via voltage divider for 3.3V logic)
• AT-09 RXD → Arduino Pin 11 (TX)

#include <SoftwareSerial.h>

// Define RX and TX pins for SoftwareSerial
SoftwareSerial BTSerial(10, 11); // RX = Pin 10, TX = Pin 11

void setup() {
  Serial.begin(9600); // Start Serial Monitor at 9600 bps
  BTSerial.begin(9600); // Start Bluetooth communication at 9600 bps

  Serial.println("AT-09 Bluetooth Module Test");
  Serial.println("Send data via Serial Monitor to communicate with the module.");
}

void loop() {
  // Check if data is available from the Bluetooth module
  if (BTSerial.available()) {
    char c = BTSerial.read(); // Read a character from the module
    Serial.write(c); // Forward the character to the Serial Monitor
  }

  // Check if data is available from the Serial Monitor
  if (Serial.available()) {
    char c = Serial.read(); // Read a character from the Serial Monitor
    BTSerial.write(c); // Forward the character to the Bluetooth module
  }
}

• Use a voltage divider on the Arduino TX pin to step down the 5V signal to 3.3V for the AT-09 RXD pin.
• Open the Serial Monitor and set the baud rate to 9600 bps to test communication.

1. Module Not Detected by BLE Device:

   • Ensure the module is powered correctly (check VCC and GND connections).
   • Verify the EN pin is HIGH to enable the module.
   • Check for interference or move closer to the module.

2. No Data Transmission:

   • Confirm the TXD and RXD connections are correct.
   • Ensure the baud rate of the microcontroller matches the module's default baud rate (9600 bps).
   • Use a level shifter if the microcontroller operates at 5V logic levels.

3. Short Range or Unstable Connection:

   • Ensure there are no physical obstructions or sources of interference (e.g., Wi-Fi routers).
   • Check the power supply for stability.

4. Unable to Change Baud Rate or Settings:

   • Use AT commands to configure the module. For example, send AT+BAUD4 to set the baud rate to 9600 bps.
   • Ensure the module is in command mode (not connected to another device).

Q: Can the AT-09 module be used with a 5V microcontroller?
A: Yes, but you must use a voltage divider or level shifter to step down the 5V UART signals to 3.3V for the module's RXD pin.

Q: What is the default pairing code for the AT-09?
A: The default pairing code is typically 123456. Check the manufacturer's documentation if this does not work.

Q: How do I reset the module to factory settings?
A: Send the AT command AT+RENEW followed by AT+RESET to restore factory settings.

Q: Can the AT-09 module be used for audio streaming?
A: No, the AT-09 is designed for data transfer and does not support audio streaming.

By following this documentation, you can effectively integrate the AT-09 Bluetooth module into your projects for reliable wireless communication.