ADXL345 accelerometer with ESP32

Specifications

Power and logic levels

3.3 V: safe to connect directly

ESP32 pins, including those on a display board's connectors, work at 3.3 V and are not 5 V tolerant. Modules differ, so if in doubt, measure the signal before you connect it.

Wiring

Arduino code

#include <Wire.h>

const int SDA_PIN = 8, SCL_PIN = 9;
const uint8_t ADDR = 0x53;

void writeReg(uint8_t reg, uint8_t value) {
  Wire.beginTransmission(ADDR);
  Wire.write(reg); Wire.write(value);
  Wire.endTransmission();
}

void setup() {
  Serial.begin(115200);
  Wire.begin(SDA_PIN, SCL_PIN);
  Wire.beginTransmission(ADDR);
  Wire.write(0x00);
  Wire.endTransmission();
  Wire.requestFrom(ADDR, (uint8_t)1);
  Serial.printf("Device ID 0x%02X\n", Wire.read());   // expect 0xE5
  writeReg(0x31, 0x0B);               // full resolution, +/-16 g
  writeReg(0x2D, 0x08);               // measure
}

void loop() {
  Wire.beginTransmission(ADDR);
  Wire.write(0x32);
  Wire.endTransmission();
  Wire.requestFrom(ADDR, (uint8_t)6);
  int16_t v[3];
  for (int i = 0; i < 3; i++) {       // low byte first
    uint8_t lo = Wire.read();
    v[i] = lo | (Wire.read() << 8);
  }
  Serial.printf("x %.2f  y %.2f  z %.2f g\n", v[0] * 0.004, v[1] * 0.004, v[2] * 0.004);
  delay(200);
}

No extra library needed. Compiled for ESP32-S3 with arduino-esp32 3.x. Not yet tested by us on a physical sensor. Change the pins to match your board.

On a display

Read the value in your sketch and pass it to a label, or send it over MQTT and show it with an MQTT value in the editor.

Boards with a ready connector

Only boards whose connectors we have surveyed. Others may still work on free GPIOs.

Good to know

• Do not leave SDO floating.
• CS must be high for I2C.
• It has no gyro.
• Mount it rigidly for vibration work.

What it is good for

• Wake on tap
• Tilt displays
• Drop and shock detection

FAQ

Sources

• https://learn.adafruit.com/adxl345-digital-accelerometer/pinouts
• https://people.ece.ubc.ca/edc/7660.jan2018/ADXL345.pdf
• https://docs.viam.com/reference/components/movement-sensor/micro-rdk/accel-adxl345/

Related parts

• MPU6050
• AS5600 magnetic encoder