ADXL345 on OLED: 3-Axis Accelerometer
Overview & Wiring
What it is: The ADXL345 is a small, low-power 3-axis accelerometer with excellent resolution. It's ideal for tilt sensing, tap/double-tap detection, freefall detection, and vibration monitoring.
How it works: I2C device at address 0x53. It measures acceleration on X/Y/Z in g (or m/s²); at rest, gravity registers as ~9.8 m/s² on the vertical axis. Shares SDA/SCL with the OLED.
Wiring (shared I2C bus with the OLED):
ADXL345 SDA -> GPIO4
ADXL345 SCL -> GPIO5
ADXL345 VCC -> 3V3
ADXL345 GND -> GND
OLED VCC=3V3, GND=GND, SDA=GPIO4, SCL=GPIO5
Libraries: "Adafruit ADXL345" (installs "Adafruit Unified Sensor" and "Adafruit BusIO"), plus "Adafruit SSD1306" and "Adafruit GFX Library".
On screen / Serial: acceleration X/Y/Z in m/s². Tap or tilt the board to see the values respond.
Gotchas: Default address is 0x53 (0x1D if the SDO pin is tied high). It's a 3.3V part — don't feed VCC 5V unless your board has a regulator. Choose the ±2g range (default) for the finest resolution.
Circuit Diagram
Parts You Need
Source Code (Arduino / ESP32)
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <Adafruit_ADXL345_U.h>
Adafruit_SSD1306 display(128, 64, &Wire, -1);
Adafruit_ADXL345_Unified accel = Adafruit_ADXL345_Unified(12345);
void setup() {
Serial.begin(115200);
Wire.begin(4, 5);
display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
if (!accel.begin()) {
Serial.println("ADXL345 not found");
display.setTextColor(SSD1306_WHITE);
display.setCursor(0, 28); display.println("ADXL345 not found");
display.display();
while (1) delay(10);
}
accel.setRange(ADXL345_RANGE_2_G);
}
void loop() {
sensors_event_t e;
accel.getEvent(&e);
display.clearDisplay();
display.setTextColor(SSD1306_WHITE);
display.setTextSize(1);
display.setCursor(0, 0); display.println("ADXL345 m/s2");
display.setTextSize(2);
display.setCursor(0, 14); display.printf("X %.1f", e.acceleration.x);
display.setCursor(0, 32); display.printf("Y %.1f", e.acceleration.y);
display.setCursor(0, 50); display.setTextSize(1); display.printf("Z %.2f", e.acceleration.z);
display.display();
Serial.printf("X %.2f Y %.2f Z %.2f m/s2\n",
e.acceleration.x, e.acceleration.y, e.acceleration.z);
delay(200);
}