🛠 Lire l'accélération avec l'IMU MPU6886

Objectives

Read the 3 acceleration axes of the MPU6886 (6-axis IMU: accelerometer + gyroscope) connected to the internal I2C bus SDA=G21 / SCL=G22, the same bus as the BM8563 real-time clock (standard I2C addresses: 0x68 for the MPU6886, 0x51 for the BM8563). Display ax, ay, az in g on the screen and on the serial monitor.

Hardware

• 1× M5StickC Plus2 (v2)
• USB-C cable + CH9102 driver
• Arduino IDE / PlatformIO, M5Unified library

Complete code

// IMU MPU6886 sur I2C interne SDA=G21 SCL=G22 (adresse 0x68)
#include <M5Unified.h>

void setup {
  auto cfg = M5.config;
  M5.begin(cfg);
  Serial.begin(115200);
  M5.Display.setRotation(1);
  M5.Display.setTextSize(2);
  M5.Display.setTextColor(TFT_CYAN, TFT_BLACK);
  if (!M5.Imu.isEnabled) {
    M5.Display.println("IMU absente!");   // MPU6886 introuvable sur 0x68
  }
}

void loop {
  M5.update;
  float ax = 0, ay = 0, az = 0;
  M5.Imu.getAccel(&ax, &ay, &az);        // en g (1 g = 9.81 m/s2)
  M5.Display.setCursor(0, 10);
  M5.Display.printf("ax %+5.2f g\n", ax);
  M5.Display.printf("ay %+5.2f g\n", ay);
  M5.Display.printf("az %+5.2f g\n", az);
  Serial.printf("%f %f %f\n", ax, ay, az);
  vTaskDelay(100 / portTICK_PERIOD_MS);
}

Expected verification

When placed flat, the screen displays approximately az = +1.00 g and ax/ay close to 0; when tilted on its edge, the corresponding axis moves to ±1 g. The serial monitor outputs 10 lines per second. A small I2C scanner (Wire.begin(21, 22)) finds 0x68 (IMU) and 0x51 (RTC).

Common errors

• Scanning the wrong bus: the Grove HY2.0-4P connector (PORT.CUSTOM, G32/G33) is a separate I2C bus from the internal G21/G22 bus.
• Using the old API M5.Power.* or the deprecated library M5StickCPlus2.h: the v2 no longer has an AXP192 PMIC and the library is no longer maintained.
• Expecting degrees or m/s²: getAccel returns values in g; convert them yourself if needed.
• Not testing M5.Imu.isEnabled and displaying zeros without understanding why (wrong bus, wrong board).
• Confusing the accelerometer and the gyroscope: getGyro returns angular velocity, not tilt.