How to Use ADXL345: Examples, Pinouts, and Specs

The ADXL345 is a small, thin, low-power, 3-axis accelerometer manufactured by Arduino (Part ID: UNO). It offers high-resolution (13-bit) measurements of acceleration up to ±16g. This versatile sensor is designed for applications requiring motion sensing, tilt detection, and gesture recognition. Its ability to communicate via I2C or SPI makes it suitable for integration into a wide range of electronic projects, including robotics, wearable devices, and gaming systems.

• Motion sensing in robotics and drones
• Tilt detection in portable devices
• Gesture recognition in gaming controllers
• Vibration monitoring in industrial systems
• Step counting and activity tracking in fitness devices

The ADXL345 is packed with features that make it a popular choice for motion sensing applications. Below are its key technical specifications:

The ADXL345 has the following pin configuration:

To use the ADXL345 with an Arduino UNO, follow these steps:

1. Wiring: Connect the ADXL345 to the Arduino UNO as shown below:

   • VCC → 3.3V
   • GND → GND
   • SDA → A4 (on older Arduino boards) or SDA pin
   • SCL → A5 (on older Arduino boards) or SCL pin
   • CS → GND (for I2C mode)
   • SDO → GND (for default I2C address)

2. Install Libraries: Install the Adafruit_ADXL345 library from the Arduino Library Manager for easy interfacing.

3. Upload Code: Use the following example code to read acceleration data from the ADXL345:

#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_ADXL345_U.h>

// Create an ADXL345 object
Adafruit_ADXL345_Unified accel = Adafruit_ADXL345_Unified(12345);

void setup() {
  Serial.begin(9600);
  // Initialize the ADXL345
  if (!accel.begin()) {
    Serial.println("Failed to find ADXL345 chip. Check connections.");
    while (1);
  }
  Serial.println("ADXL345 initialized successfully!");

  // Set range to ±16g for maximum sensitivity
  accel.setRange(ADXL345_RANGE_16_G);
}

void loop() {
  sensors_event_t event;
  accel.getEvent(&event);

  // Print acceleration data
  Serial.print("X: "); Serial.print(event.acceleration.x); Serial.print(" m/s^2 ");
  Serial.print("Y: "); Serial.print(event.acceleration.y); Serial.print(" m/s^2 ");
  Serial.print("Z: "); Serial.print(event.acceleration.z); Serial.println(" m/s^2");

  delay(500); // Delay for readability
}

• Power Supply: Ensure the ADXL345 is powered with 3.3V. Using 5V may damage the sensor.
• Pull-Up Resistors: If your Arduino board does not have built-in pull-up resistors on the I2C lines, add external 4.7kΩ resistors between SDA/SCL and VCC.
• Range Configuration: Adjust the measurement range (±2g, ±4g, ±8g, or ±16g) based on your application using the setRange() function.

1. No Data Output:

   • Cause: Incorrect wiring or loose connections.
   • Solution: Double-check all connections and ensure SDA/SCL are connected to the correct pins.

2. Initialization Fails:

   • Cause: Incorrect I2C address or damaged sensor.
   • Solution: Verify the I2C address (default is 0x53). Replace the sensor if damaged.

3. Inconsistent Readings:

   • Cause: Electrical noise or improper grounding.
   • Solution: Ensure proper grounding and use decoupling capacitors if necessary.

Q1: Can the ADXL345 be used with 5V logic?
A1: No, the ADXL345 operates at 3.3V. Use a logic level shifter if interfacing with a 5V system.

Q2: How do I switch to SPI communication?
A2: Connect the CS pin to a digital pin on the Arduino and configure the library for SPI mode.

Q3: What is the maximum sampling rate of the ADXL345?
A3: The ADXL345 supports output data rates up to 3200 Hz.

By following this documentation, you can successfully integrate the ADXL345 into your projects for reliable motion sensing and acceleration measurements.