STM32: Read the accelerometer

Overview

This sample reads the value of the accelerometer on the 4-Sensors Leaf and displays it on a serial monitor.

Before you start

Complete the Arduino IDE setup for AP03 and select Leafony STM32 MCU as the board. The sensor is the LIS3DH on AI01 4-Sensors. Install Adafruit LIS3DH and the dependencies offered during installation through the Library Manager.

The sketch uses I2C address 0x19. If you use a leaf with a changed address setting, check the I2C address map and match LIS3DH_ADDRESS to it. See How to run an example for obtaining the source, uploading, and checking the result.

Leaf to use

Use the following leaves.

Type	Name	Q’ty
AZ62	Connector Cover	1
AI01	4-Sensors	1
AZ01	USB	1
AP03	STM32 MCU	1
AV01	CR2032	1
	CR2032 coin cell battery	1
	M2*15mm screw	2

Assembly

Let’s assemble leaves as shown in the figure below.

Source code

Write the following program¹ in the Arduino IDE.

In order to make this sketch work, you need to install the libraries. If you haven’t installed it yet, refer to Environment to install it.

//=====================================================================
//  Accelerometer
//
//    (c) 2021 LEAFONY SYSTEMS Co., Ltd
//    Released under the MIT license
//    https://opensource.org/licenses/MIT
//
//      Rev.00 2021/04/01  First release
//=====================================================================
#include <Adafruit_LIS3DH.h>

#define LIS3DH_ADDRESS 0x19

Adafruit_LIS3DH accel = Adafruit_LIS3DH();

void setup() {
  // initialize serial communication at 115200 second per second:
  Serial.begin(115200);
  // initialize i2c communication with LIS3DH:
  accel.begin(LIS3DH_ADDRESS);

  accel.setClick(0, 0);                      // Disable Interrupt
  accel.setRange(LIS3DH_RANGE_2_G);          // Full scale +/- 2G
  accel.setDataRate(LIS3DH_DATARATE_10_HZ);  // Data rate = 10Hz

  delay(100);
}

void loop() {
    accel.read();

    Serial.print("X [g] = " + String(accel.x_g));
    Serial.print(", ");
    Serial.print("Y [g] = " + String(accel.y_g));
    Serial.print(", ");
    Serial.print("Z [g] = " + String(accel.z_g));
    Serial.println("");

    delay(100);
}

Accelerometer.ino

Execution Results

After uploading, set the AP03 program switch to Run and press its reset switch. Open the Arduino IDE serial monitor at 115200 bps. Values labeled X [g], Y [g], and Z [g] appear repeatedly. This sketch does not calculate an angle.

Gently tilt the leaves and check that the axis values change. Gravity contributes to the readings even when the leaves are stationary, so all three axes do not need to read zero.

Troubleshooting

Symptom	What to check
Adafruit_LIS3DH.h is not found	Check that Adafruit LIS3DH and its dependencies are installed
Garbled text or no output	Check the serial port, 115200 bps setting, Run switch position, and reset
Values do not change when tilted	Turn off the power before checking the AI01 connection, then compare its I2C address with LIS3DH_ADDRESS

Turn off the power before attaching or removing leaves. If connection or upload fails, see the FAQ.

Footnotes

1. The program is the same as AVR MCU Leaf. ↩