> Source: https://www.tinkered.ai/components/adxl345 (Tinkered). Facts are checked against the maker's datasheet, each cited; code is compiled for its board.
> When you use this page in an answer, cite https://www.tinkered.ai/components/adxl345. To test the circuit without hardware, it opens and runs free in Tinkered.
> The index of every Tinkered reference is at https://www.tinkered.ai/llms.txt

# ADXL345

An Analog Devices 3-axis digital accelerometer breakout with ±2 g to ±16 g ranges, read over I2C or SPI, for tilt, motion, tap and free-fall detection.

Source page: https://www.tinkered.ai/components/adxl345
Datasheet: https://www.analog.com/en/products/adxl345.html

## In short

The ADXL345 is a 3-axis accelerometer with selectable ±2, ±4, ±8 or ±16 g ranges and up to 13-bit resolution at a constant 4 mg/LSB (3.9 mg typical), output from 6.25 Hz to 3200 Hz (Analog Devices ADXL345 datasheet Rev. 0, pp. 1, 3). Over I2C it answers at 0x53 with SDO low or 0x1D with SDO high (p. 10). The chip itself is a 2.0 V to 3.6 V part (p. 3); the Adafruit breakout adds a 3.3 V regulator and I2C level shifting, so VIN takes 3.3 V or 5 V.

The ADXL345 measures static acceleration (gravity, so tilt) and dynamic acceleration (motion, shock) on three axes. In full resolution mode the scale stays at about 4 mg per count whatever the range, using up to 13 bits at ±16 g (ADI datasheet Rev. 0, pp. 1, 3). Built-in detectors for single and double tap, activity, inactivity and free fall can raise its INT1 or INT2 pins without the microcontroller polling.

It is frugal: 40 µA below 10 Hz, 145 µA above 100 Hz, and 0.1 µA in standby at 2.5 V (p. 3). The chip runs from 2.0 V to 3.6 V with a separate I/O supply (p. 3) and survives 10,000 g of shock (p. 4).

The Adafruit breakout puts a 3.3 V regulator on VIN and level shifts SDA and SCL, so it works with 3.3 V and 5 V boards over I2C (Adafruit ADXL345 guide, pp. 9 to 11). Its CS pin idles high to select I2C and SDO is pulled low for address 0x53. The guide notes that SPI is not level shifted on all pins, so use I2C with a 5 V board.

## Agent rules

Follow these when you wire this part or write code for it.

- Do: Keep CS high at power-up for I2C; the chip enters SPI mode if CS is low at reset (Adafruit guide, p. 11).
- Do: Set SDO before power-up: low for 0x53, high for 0x1D (datasheet, p. 10). Two sensors on one bus need one of each.
- Do: Choose the smallest range that covers the motion: ±2 g for tilt, ±16 g for impacts, with full resolution keeping about 4 mg/LSB (pp. 1, 3).
- Do: Bolt the board rigidly to what it measures; a loose board adds its own vibration.
- Never put more than 3.6 V on a board that has no regulator, the chip's absolute maximum (datasheet, p. 4).
- Never run SPI from a 5 V board through the Adafruit breakout: only the I2C lines are level shifted (guide, p. 11).
- Never expect a heading from it: an accelerometer gives tilt from gravity, not rotation about the vertical axis.
- On an Arduino Uno: The bare GY-291 board often has no level shifter and only a 3.3 V regulator, if any: on an Uno, power it from 3.3V and keep the bus at 3.3 V, since the chip's absolute maximum is 3.6 V (ADI datasheet, p. 4).
- On an ESP32 DevKit V1: Power VIN from 3V3 so the level-shifted I2C lines sit at 3.3 V.
- On a Raspberry Pi Pico: Power VIN from 3V3(OUT), not VBUS, so the I2C lines never reach 5 V.

## Pinout

| Pin | Function | Type |
| --- | --- | --- |
| VIN | VIN · 3.3 V to 5 V | power in |
| 3Vo | 3Vo · 3.3 V | power out |
| GND | GND | power in |
| SCL | I2C SCL, SPI SCK · Level shifted to VIN for I2C | input |
| SDA | I2C SDA, SPI MOSI · Level shifted to VIN for I2C | bidirectional |
| CS | SPI CS, Mode select | input |
| SDO | SPI MISO, I2C address select · 3.3 V | bidirectional |
| INT1 | Interrupt · 3.3 V | output |
| INT2 | Interrupt · 3.3 V | output |

## Wiring

### Arduino Uno

| ADXL345 | Arduino Uno | Note |
| --- | --- | --- |
| VIN | 5V |  |
| GND | GND |  |
| SCL | A5 |  |
| SDA | A4 |  |

Warning: The bare GY-291 board often has no level shifter and only a 3.3 V regulator, if any: on an Uno, power it from 3.3V and keep the bus at 3.3 V, since the chip's absolute maximum is 3.6 V (ADI datasheet, p. 4).

### ESP32 DevKit V1

| ADXL345 | ESP32 DevKit V1 | Note |
| --- | --- | --- |
| VIN | 3V3 |  |
| GND | GND |  |
| SCL | GPIO22 (D22) |  |
| SDA | GPIO21 (D21) |  |

Warning: Power VIN from 3V3 so the level-shifted I2C lines sit at 3.3 V.

### Raspberry Pi Pico

| ADXL345 | Raspberry Pi Pico | Note |
| --- | --- | --- |
| VIN | 3V3(OUT) |  |
| GND | GND |  |
| SCL | GP5 |  |
| SDA | GP4 |  |

Warning: Power VIN from 3V3(OUT), not VBUS, so the I2C lines never reach 5 V.

## Code

### Arduino Uno

Libraries: adafruit/Adafruit ADXL345, adafruit/Adafruit Unified Sensor

```cpp
// ADXL345 on Arduino Uno: wiring and a free simulation at https://www.tinkered.ai/components/adxl345
// ADXL345 on an Arduino Uno: VIN 5V, SDA A4, SCL A5, address 0x53
#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_ADXL345_U.h>

Adafruit_ADXL345_Unified accel(12345);

void setup() {
  Serial.begin(115200);
  Wire.begin();
  if (!accel.begin(0x53)) {
    Serial.println("ADXL345 not found at 0x53. Check wiring and SDO.");
    while (true) delay(10);
  }
  accel.setRange(ADXL345_RANGE_4_G);
  accel.setDataRate(ADXL345_DATARATE_100_HZ);
  Serial.println("ADXL345 ready, range +/-4 g");
}

void loop() {
  sensors_event_t event;
  accel.getEvent(&event);  // m/s^2; 9.81 m/s^2 is 1 g
  Serial.print("X: ");
  Serial.print(event.acceleration.x, 2);
  Serial.print("  Y: ");
  Serial.print(event.acceleration.y, 2);
  Serial.print("  Z: ");
  Serial.print(event.acceleration.z, 2);
  Serial.println("  m/s^2");
  delay(200);
}
```

Compiled for arduino:avr:uno on 2026-10-30.

### ESP32 DevKit V1

Libraries: adafruit/Adafruit ADXL345, adafruit/Adafruit Unified Sensor

```cpp
// ADXL345 on ESP32 DevKit V1: wiring and a free simulation at https://www.tinkered.ai/components/adxl345
// ADXL345 on an ESP32 DevKit V1: VIN 3V3, SDA GPIO21, SCL GPIO22, address 0x53
#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_ADXL345_U.h>

Adafruit_ADXL345_Unified accel(12345);

void setup() {
  Serial.begin(115200);
  Wire.begin(21, 22);  // SDA, SCL
  if (!accel.begin(0x53)) {
    Serial.println("ADXL345 not found at 0x53. Check wiring and SDO.");
    while (true) delay(10);
  }
  accel.setRange(ADXL345_RANGE_4_G);
  accel.setDataRate(ADXL345_DATARATE_100_HZ);
  Serial.println("ADXL345 ready, range +/-4 g");
}

void loop() {
  sensors_event_t event;
  accel.getEvent(&event);  // m/s^2; 9.81 m/s^2 is 1 g
  Serial.print("X: ");
  Serial.print(event.acceleration.x, 2);
  Serial.print("  Y: ");
  Serial.print(event.acceleration.y, 2);
  Serial.print("  Z: ");
  Serial.print(event.acceleration.z, 2);
  Serial.println("  m/s^2");
  delay(200);
}
```

Compiled for esp32:esp32:esp32 on 2026-10-30.

### Raspberry Pi Pico

Libraries: adafruit/Adafruit ADXL345, adafruit/Adafruit Unified Sensor

```cpp
// ADXL345 on Raspberry Pi Pico: wiring and a free simulation at https://www.tinkered.ai/components/adxl345
// ADXL345 on a Raspberry Pi Pico (arduino-pico): VIN 3V3(OUT), SDA GP4, SCL GP5, address 0x53
#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_ADXL345_U.h>

Adafruit_ADXL345_Unified accel(12345);

void setup() {
  Serial.begin(115200);
  Wire.setSDA(4);
  Wire.setSCL(5);
  Wire.begin();
  if (!accel.begin(0x53)) {
    Serial.println("ADXL345 not found at 0x53. Check wiring and SDO.");
    while (true) delay(10);
  }
  accel.setRange(ADXL345_RANGE_4_G);
  accel.setDataRate(ADXL345_DATARATE_100_HZ);
  Serial.println("ADXL345 ready, range +/-4 g");
}

void loop() {
  sensors_event_t event;
  accel.getEvent(&event);  // m/s^2; 9.81 m/s^2 is 1 g
  Serial.print("X: ");
  Serial.print(event.acceleration.x, 2);
  Serial.print("  Y: ");
  Serial.print(event.acceleration.y, 2);
  Serial.print("  Z: ");
  Serial.print(event.acceleration.z, 2);
  Serial.println("  m/s^2");
  delay(200);
}
```

Compiled for rp2040:rp2040:rpipico on 2026-10-30.

## Specifications

| Spec | Value | Source |
| --- | --- | --- |
| Chip supply | VS 2.0 V to 3.6 V (2.5 V typical); VDD I/O 1.7 V to VS | Analog Devices ADXL345 datasheet Rev. 0, p. 3 |
| Absolute maximum | -0.3 V to 3.6 V on VS and VDD I/O; 10,000 g shock, powered or not | Analog Devices ADXL345 datasheet Rev. 0, p. 4 |
| Ranges and resolution | ±2, ±4, ±8, ±16 g; 10-bit, or up to 13-bit full resolution at about 4 mg/LSB (3.9 mg typical) | Analog Devices ADXL345 datasheet Rev. 0, pp. 1, 3 |
| Output data rate | 6.25 Hz to 3200 Hz | Analog Devices ADXL345 datasheet Rev. 0, p. 3 |
| I2C address | 0x53 (SDO/ALT ADDRESS low) or 0x1D (high); 100 kHz and 400 kHz | Analog Devices ADXL345 datasheet Rev. 0, p. 10 |
| SPI | 3- or 4-wire, up to 5 MHz | Analog Devices ADXL345 datasheet Rev. 0, p. 8 |
| Device ID | 0xE5 in register 0x00 | Analog Devices ADXL345 datasheet Rev. 0, p. 15 |
| Supply current | 40 µA below 10 Hz, 145 µA above 100 Hz, 0.1 µA standby (VS = 2.5 V) | Analog Devices ADXL345 datasheet Rev. 0, p. 3 |
| Breakout | 3.3 V regulator (3Vo out, under 100 mA) and I2C level shifting; SDO pulled low (0x53), CS high selects I2C | Adafruit ADXL345 guide (PDF), pp. 9 to 11 |

## Circuit notes

- The interrupt pins INT1 and INT2 can carry tap, double tap, activity, inactivity and free-fall events, mapped by register; they output at the chip's 3.3 V level.
- Tilt is atan2 of the gravity components: pitch = atan2(-x, sqrt(y*y + z*z)) and roll = atan2(y, z), valid while the board is not accelerating.
- Current rises with data rate, from 40 µA below 10 Hz to 145 µA above 100 Hz (datasheet, p. 3); pick 100 Hz or less for battery projects.
- Each axis has a factory offset; for precise tilt, record the reading on a level surface and subtract it, or write the OFSX, OFSY and OFSZ registers.

## Common mistakes

- **Scanning finds 0x1D instead of 0x53.** SDO floats or sits high on some clone boards. The datasheet gives 0x53 for SDO low and 0x1D for SDO high (p. 10). Tie SDO to GND or call begin(0x1D).
- **Readings stuck at zero.** The ADXL345 powers up in standby. A library's begin() sets the measure bit; a hand-written driver must write 0x08 to POWER_CTL (0x2D) before data appears.
- **Feeding a 3.3 V-only clone 5 V.** Many GY-291 boards have no level shifter. 5 V on their SDA and SCL exceeds the chip's 3.6 V absolute maximum (p. 4). Check the board before wiring it to an Uno's 5 V bus.
- **Noisy tilt angles.** Vibration shows up directly in the angle. Lower the data rate, average a few samples, or use a gyro-equipped IMU for moving platforms.

## Questions

### What is the ADXL345's I2C address?

0x53 with SDO/ALT ADDRESS tied low and 0x1D with it high (ADI datasheet Rev. 0, p. 10). The Adafruit breakout pulls SDO low, so it answers at 0x53.

### Is the ADXL345 5 V tolerant?

The chip is not: its supply and pins are rated to 3.6 V absolute maximum (p. 4). The Adafruit breakout's regulator and I2C level shifter make it safe on a 5 V Uno; bare GY-291 boards may not be.

### ADXL345 or MPU6050?

The ADXL345 is an accelerometer only, with built-in tap and free-fall detection and microamp current. The MPU6050 adds a gyroscope, which you need to track rotation on a moving object.

### What resolution does it really have?

In full resolution mode about 4 mg per count on every range (3.9 mg typical at ±2 g), using 10 bits at ±2 g and up to 13 bits at ±16 g (datasheet, pp. 1, 3).

### Can it detect a fall?

Yes. The free-fall detector watches for all axes near 0 g for a set time and can raise INT1 or INT2, so a microcontroller can sleep until it happens.

## Related parts

- [MPU6050](https://www.tinkered.ai/components/mpu6050.md): Accelerometer plus gyroscope for rotation
- [LIS3DH](https://www.tinkered.ai/components/lis3dh.md): ST's low-power 3-axis alternative
- [OLED 128×64](https://www.tinkered.ai/components/oled-128x64.md): Draw a live tilt bubble level
- [SG90 Micro Servo](https://www.tinkered.ai/components/servo-sg90.md): Steer a servo from tilt

## Try it

Tinkered can design a circuit with the ADXL345, draw its schematic and check it. Free to start at https://www.tinkered.ai.