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 systems.

• Motion sensing in portable devices
• Tilt and orientation detection
• Gesture recognition for user interfaces
• Vibration monitoring in industrial systems
• Gaming and virtual reality controllers

• Measurement Range: ±2g, ±4g, ±8g, ±16g (selectable)
• Resolution: 13-bit
• Supply Voltage: 2.0V to 3.6V
• Communication Protocols: I2C (up to 400 kHz) and SPI (up to 5 MHz)
• Power Consumption:
  • Normal mode: 40 µA
  • Standby mode: 0.1 µA
• Operating Temperature: -40°C to +85°C
• Output Data Rate (ODR): 0.1 Hz to 3200 Hz
• Dimensions: 3 mm × 5 mm × 1 mm (LFCSP package)

The ADXL345 has 14 pins. Below is the pinout and description:

1. Power Supply: Connect the VDD pin to a 3.3V power source and the GND pin to ground.
2. Communication Protocol:
   • For I2C: Tie the CS pin high and connect the SCL and SDA pins to the corresponding I2C lines of your microcontroller. Use pull-up resistors (typically 4.7 kΩ) on the SCL and SDA lines.
   • For SPI: Tie the CS pin low and connect the SCL, SDA, and CS pins to the corresponding SPI lines of your microcontroller.
3. Interrupts: Connect INT1 and/or INT2 to your microcontroller if you need to use interrupt-driven features.
4. Bypass Capacitor: Place a 0.1 µF ceramic capacitor close to the VDD pin for power supply decoupling.

• Voltage Levels: Ensure the logic levels of your microcontroller match the ADXL345's voltage requirements (2.0V to 3.6V).
• Mounting: Minimize mechanical stress on the ADXL345 to avoid inaccurate readings.
• Data Rate: Choose an appropriate output data rate (ODR) based on your application to balance power consumption and performance.
• Calibration: Perform calibration to account for offsets and scale factors for accurate measurements.

#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();

  // Set data format to ±2g and full resolution
  Wire.beginTransmission(ADXL345_ADDRESS);
  Wire.write(0x31); // Data format register
  Wire.write(0x08); // Full resolution, ±2g
  Wire.endTransmission();
}

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

  // Request 6 bytes of data from the ADXL345 (X, Y, Z axes)
  Wire.beginTransmission(ADXL345_ADDRESS);
  Wire.write(0x32); // Start reading from the DATAX0 register
  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 accelerometer readings
  Serial.print("X: "); Serial.print(x);
  Serial.print(" Y: "); Serial.print(y);
  Serial.print(" Z: "); Serial.println(z);

  delay(500); // Delay for readability
}

1. No Communication with the ADXL345:

   • Ensure the correct I2C address (0x53) is being used.
   • Verify pull-up resistors are present on the I2C lines.
   • Check the wiring and ensure the CS pin is tied high for I2C mode.

2. Incorrect or No Data:

   • Confirm the ADXL345 is in measurement mode (check the power control register).
   • Verify the data format register is configured correctly for your application.

3. High Noise in Readings:

   • Ensure proper decoupling capacitors are used near the power supply pins.
   • Minimize vibrations or mechanical stress on the sensor.

• Use a logic analyzer or oscilloscope to verify I2C or SPI signals.
• Check the power supply voltage to ensure it is within the specified range.
• Test the ADXL345 with a simple example code to confirm basic functionality before integrating it into a larger project.