STM32 Nucleo and ADXL337 accelerometer Arduino example

In this article we connect an ADXL337 accelerometer to an STM32 Nucleo, the example was written in the Arduino IDE

The ADXL337 is a small, thin, low power, complete 3-axis accelerometer with signal conditioned voltage outputs. The product measures acceleration with a minimum full-scale range of ±3g. It can measure the static acceleration of gravity in tiltsensing applications, as well as dynamic acceleration resulting from motion, shock, or vibration.

The user selects the bandwidth of the accelerometer using the C_X, C_Y, and C_Z capacitors at the X_OUT, Y_OUT, and Z_OUTpins. Bandwidths can be selected to suit the application, with a range of 0.5 Hz to 1600 Hz for X and Y axes, and a range of 0.5 Hz to 550 Hz for the Z axis.

Parts List

Connection

Code

No libraries required – this is a sparkfun example

[codesyntax lang=”cpp”]

// Make sure these two variables are correct for your setup
int scale = 3; // 3 (±3g) for ADXL337, 200 (±200g) for ADXL377


void setup()
{
  // Initialize serial communication at 115200 baud
  Serial.begin(115200);
}

// Read, scale, and print accelerometer data
void loop()
{
  // Get raw accelerometer data for each axis
  int rawX = analogRead(A0);
  int rawY = analogRead(A1);
  int rawZ = analogRead(A2);
  
  // Scale accelerometer ADC readings into common units
  // Scale map depends on if using a 5V or 3.3V microcontroller
  float scaledX, scaledY, scaledZ; // Scaled values for each axis
  scaledX = mapf(rawX, 0, 675, -scale, scale); // 3.3/5 * 1023 =~ 675
  scaledY = mapf(rawY, 0, 675, -scale, scale);
  scaledZ = mapf(rawZ, 0, 675, -scale, scale);

  // Print out raw X,Y,Z accelerometer readings
  Serial.print("X: "); 
  Serial.println(rawX);
  Serial.print("Y: "); 
  Serial.println(rawY);
  Serial.print("Z: "); 
  Serial.println(rawZ);
  Serial.println();
  
  // Print out scaled X,Y,Z accelerometer readings
  Serial.print("X: "); 
  Serial.print(scaledX); 
  Serial.println(" g");
  Serial.print("Y: "); 
  Serial.print(scaledY); 
  Serial.println(" g");
  Serial.print("Z: "); 
  Serial.print(scaledZ); 
  Serial.println(" g");
  Serial.println();
  
  delay(2000); // Minimum delay of 2 milliseconds between sensor reads (500 Hz)
}

// Same functionality as Arduino's standard map function, except using floats
float mapf(float x, float in_min, float in_max, float out_min, float out_max)
{
  return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}

[/codesyntax]

Output

Open the serial monitor and you will see something like this

X: 483
Y: 465
Z: 444

X: 1.29 g
Y: 1.13 g
Z: 0.95 g

X: 610
Y: 532
Z: 501

X: 2.42 g
Y: 1.73 g
Z: 1.45 g

Links

https://www.analog.com/media/en/technical-documentation/data-sheets/ADXL337.pdf