Built-in project · Arduino Uno R3

ADXL345 accelerometer on I2C, on an Arduino Uno

An ADXL345 on A4 and A5: the sketch wakes it, reads its X, Y and Z registers over I2C with Wire, and prints the raw values. The whole build, an Arduino Uno and 1 more part, runs here in your browser on the firmware below; open it in the editor to change the wiring or the code and run it again.

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The parts retail for about $30. On Mokxi they're free.

ADXL345 accelerometer on I2C · Arduino Uno R3live0.000 s 0.00x

Click to open it in the editor

The circuit itself, running here on the simulator. Press what can be pressed; click anything else to open it in the editor.

The code

The firmware exactly as the editor opens it. Change a line there and press Run: it compiles in the browser.

sketch.ino · Arduino Uno R3

// An ADXL345 accelerometer, read with nothing but Wire.
//
//   ADXL345 SDA -> A4   SCL -> A5   VCC -> 5V   GND -> GND   CS -> 3.3V
//
// The chip answers at address 0x53. Writing 0x08 to its power register
// (0x2D) starts it measuring; then six bytes from 0x32 are X, Y and Z, each
// a 16-bit number, low byte first.
//
// Drag the board to tip it.

#include <Wire.h>

const int ADDRESS = 0x53;

void writeRegister(byte reg, byte value) {
  Wire.beginTransmission(ADDRESS);
  Wire.write(reg);
  Wire.write(value);
  Wire.endTransmission();
}

void setup() {
  Serial.begin(9600);
  Wire.begin();
  writeRegister(0x2D, 0x08);
  Serial.println("Mokxi Uno: ADXL345 on A4 and A5");
}

void loop() {
  Wire.beginTransmission(ADDRESS);
  Wire.write(0x32);
  Wire.endTransmission();
  Wire.requestFrom(ADDRESS, 6);
  int axes[3];
  for (int i = 0; i < 3; i++) {
    byte low = Wire.read();
    byte high = Wire.read();
    axes[i] = (int)((high << 8) | low);
  }
  Serial.print("x ");
  Serial.print(axes[0]);
  Serial.print("  y ");
  Serial.print(axes[1]);
  Serial.print("  z ");
  Serial.println(axes[2]);
  delay(300);
}