How to Use ADXL345: Examples, Pinouts, and Specs

The ADXL345 is a small, thin, low-power, 3-axis accelerometer capable of high-resolution (13-bit) measurements at up to ±16g. It is designed for applications requiring precise motion sensing, tilt detection, and gesture recognition. The device supports both I2C and SPI communication protocols, making it versatile and easy to integrate into a wide range of projects.

• Motion sensing in mobile devices
• Tilt detection in gaming controllers
• Gesture recognition in wearable devices
• Vibration monitoring in industrial equipment
• Step counting in fitness trackers

Below are the key technical details of the ADXL345:

The ADXL345 has 14 pins, but not all are required for basic operation. Below is the pin configuration:

The ADXL345 can be connected to an Arduino UNO using the I2C protocol. Below is the wiring guide:

The following code demonstrates how to read acceleration data from the ADXL345 using the I2C protocol:

#include <Wire.h> // Include the Wire library for I2C communication

#define ADXL345_ADDRESS 0x53 // I2C address of the ADXL345

void setup() {
  Wire.begin(); // Initialize I2C communication
  Serial.begin(9600); // Start serial communication for debugging

  // Initialize the ADXL345
  Wire.beginTransmission(ADXL345_ADDRESS);
  Wire.write(0x2D); // Power control register
  Wire.write(0x08); // Set the device to measurement mode
  Wire.endTransmission();
}

void loop() {
  int16_t x, y, z;

  // Request 6 bytes of data (X, Y, Z axes)
  Wire.beginTransmission(ADXL345_ADDRESS);
  Wire.write(0x32); // Start reading from the data registers
  Wire.endTransmission(false);
  Wire.requestFrom(ADXL345_ADDRESS, 6);

  if (Wire.available() == 6) {
    x = (Wire.read() | (Wire.read() << 8)); // Combine low and high bytes for X-axis
    y = (Wire.read() | (Wire.read() << 8)); // Combine low and high bytes for Y-axis
    z = (Wire.read() | (Wire.read() << 8)); // Combine low and high bytes for Z-axis
  }

  // Print the acceleration values
  Serial.print("X: "); Serial.print(x);
  Serial.print(" Y: "); Serial.print(y);
  Serial.print(" Z: "); Serial.println(z);

  delay(500); // Wait for 500ms before the next reading
}

1. Power Supply: Ensure the ADXL345 is powered with a voltage between 2.0V and 3.6V. Using 5V may damage the device.
2. Pull-Up Resistors: For I2C communication, ensure pull-up resistors (typically 4.7kΩ) are connected to the SDA and SCL lines.
3. Interrupts: The INT1 and INT2 pins can be configured for specific events like free-fall detection or activity monitoring.
4. Data Rate: Adjust the data output rate based on your application to balance power consumption and performance.

1. No Data Output:

   • Ensure the ADXL345 is properly powered and connected.
   • Verify the I2C address (default is 0x53) and adjust in the code if necessary.
   • Check for loose or incorrect wiring.

2. Incorrect or Unstable Readings:

   • Ensure the device is securely mounted to avoid vibrations.
   • Verify that the power supply voltage is stable and within the specified range.
   • Check for noise on the I2C lines and use shorter wires if necessary.

3. Device Not Detected:

   • Confirm that the CS pin is tied to 3.3V for I2C mode.
   • Use an I2C scanner sketch to detect the device address.

Q: Can the ADXL345 operate at 5V?
A: No, the ADXL345 operates at a maximum of 3.6V. Use a voltage regulator or level shifter if interfacing with a 5V system.

Q: How do I change the measurement range?
A: Write to the DATA_FORMAT register (0x31) to set the range to ±2g, ±4g, ±8g, or ±16g.

Q: Can I use SPI instead of I2C?
A: Yes, the ADXL345 supports SPI communication. Connect the CS pin to GND to enable SPI mode and configure the SPI settings in your microcontroller.

Q: What is the maximum sampling rate?
A: The ADXL345 supports a maximum data output rate of 3200 Hz. Adjust the BW_RATE register (0x2C) to set the desired rate.