ICM_20948 Mag Reads 0

gmcgee · August 10, 2025, 1:35am

^Title

Setup:
I’ve tried using the Adafruit ICM as well as a 3D party ICM ( ICM-20948 9DoF IMU, 9-Axis Motion Tracking, Digital Motion Processor, Accelerometer, Gyroscope, Magnetometer, I2C & SPI: Amazon.com: Industrial & Scientific ) from amazon (it doesn’t work with both of them). I have an Arduino Giga R1 Wifi that i’m using to plug in the code. Using I2C wiring.

Code:
I’ve used the sparkfun ICM20948 library as well as the Adafruit ICM20X libraries and I’ve run the example code from both of them (Example1 basics for sparkfun and the ICM_20948 code from the adafruit).

I’m getting either a value of 0 across all axes for the magnetometer or a random value that doesn’t change, even when a magnet is brought close to the sensor. All the other readings are working fine (gyro, accel, temp) except magnetometer. Does anyone know why this is happening?

Wiring:

Edit: The sensor that I thought was from adafruit was actually also another 3rd party sensor ( Amazon.com: CJLHENZM 1Pcs/lot TDK InvenSense ICM-20948 Module 9-DoF IMU-Stemma QT/Qwiic : Industrial & Scientific )

// Basic demo for accelerometer readings from Adafruit ICM20948
// adafruit_icm20948_test from Adafruit ICM20X library 
#include <Adafruit_ICM20X.h>
#include <Adafruit_ICM20948.h>
#include <Adafruit_Sensor.h>
#include <Wire.h>

Adafruit_ICM20948 icm;
uint16_t measurement_delay_us = 65535; // Delay between measurements for testing
// For SPI mode, we need a CS pin
#define ICM_CS 10
// For software-SPI mode we need SCK/MOSI/MISO pins
#define ICM_SCK 13
#define ICM_MISO 12
#define ICM_MOSI 11

void setup(void) {
  Serial.begin(115200);
  while (!Serial)
    delay(10); // will pause Zero, Leonardo, etc until serial console opens

  Serial.println("Adafruit ICM20948 test!");

  // Try to initialize!
  if (!icm.begin_I2C()) {
    // if (!icm.begin_SPI(ICM_CS)) {
    // if (!icm.begin_SPI(ICM_CS, ICM_SCK, ICM_MISO, ICM_MOSI)) {

    Serial.println("Failed to find ICM20948 chip");
    while (1) {
      delay(10);
    }
  }
  Serial.println("ICM20948 Found!");
  // icm.setAccelRange(ICM20948_ACCEL_RANGE_16_G);
  Serial.print("Accelerometer range set to: ");
  switch (icm.getAccelRange()) {
  case ICM20948_ACCEL_RANGE_2_G:
    Serial.println("+-2G");
    break;
  case ICM20948_ACCEL_RANGE_4_G:
    Serial.println("+-4G");
    break;
  case ICM20948_ACCEL_RANGE_8_G:
    Serial.println("+-8G");
    break;
  case ICM20948_ACCEL_RANGE_16_G:
    Serial.println("+-16G");
    break;
  }
  Serial.println("OK");

  // icm.setGyroRange(ICM20948_GYRO_RANGE_2000_DPS);
  Serial.print("Gyro range set to: ");
  switch (icm.getGyroRange()) {
  case ICM20948_GYRO_RANGE_250_DPS:
    Serial.println("250 degrees/s");
    break;
  case ICM20948_GYRO_RANGE_500_DPS:
    Serial.println("500 degrees/s");
    break;
  case ICM20948_GYRO_RANGE_1000_DPS:
    Serial.println("1000 degrees/s");
    break;
  case ICM20948_GYRO_RANGE_2000_DPS:
    Serial.println("2000 degrees/s");
    break;
  }

  //  icm.setAccelRateDivisor(4095);
  uint16_t accel_divisor = icm.getAccelRateDivisor();
  float accel_rate = 1125 / (1.0 + accel_divisor);

  Serial.print("Accelerometer data rate divisor set to: ");
  Serial.println(accel_divisor);
  Serial.print("Accelerometer data rate (Hz) is approximately: ");
  Serial.println(accel_rate);

  //  icm.setGyroRateDivisor(255);
  uint8_t gyro_divisor = icm.getGyroRateDivisor();
  float gyro_rate = 1100 / (1.0 + gyro_divisor);

  Serial.print("Gyro data rate divisor set to: ");
  Serial.println(gyro_divisor);
  Serial.print("Gyro data rate (Hz) is approximately: ");
  Serial.println(gyro_rate);

  // icm.setMagDataRate(AK09916_MAG_DATARATE_10_HZ);
  Serial.print("Magnetometer data rate set to: ");
  switch (icm.getMagDataRate()) {
  case AK09916_MAG_DATARATE_SHUTDOWN:
    Serial.println("Shutdown");
    break;
  case AK09916_MAG_DATARATE_SINGLE:
    Serial.println("Single/One shot");
    break;
  case AK09916_MAG_DATARATE_10_HZ:
    Serial.println("10 Hz");
    break;
  case AK09916_MAG_DATARATE_20_HZ:
    Serial.println("20 Hz");
    break;
  case AK09916_MAG_DATARATE_50_HZ:
    Serial.println("50 Hz");
    break;
  case AK09916_MAG_DATARATE_100_HZ:
    Serial.println("100 Hz");
    break;
  }
  Serial.println();

}

void loop() {

  //  /* Get a new normalized sensor event */
  sensors_event_t accel;
  sensors_event_t gyro;
  sensors_event_t mag;
  sensors_event_t temp;
  icm.getEvent(&accel, &gyro, &temp, &mag);

  Serial.print("\t\tTemperature ");
  Serial.print(temp.temperature);
  Serial.println(" deg C");

  /* Display the results (acceleration is measured in m/s^2) */
  Serial.print("\t\tAccel X: ");
  Serial.print(accel.acceleration.x);
  Serial.print(" \tY: ");
  Serial.print(accel.acceleration.y);
  Serial.print(" \tZ: ");
  Serial.print(accel.acceleration.z);
  Serial.println(" m/s^2 ");

  Serial.print("\t\tMag X: ");
  Serial.print(mag.magnetic.x);
  Serial.print(" \tY: ");
  Serial.print(mag.magnetic.y);
  Serial.print(" \tZ: ");
  Serial.print(mag.magnetic.z);
  Serial.println(" uT");

  /* Display the results (acceleration is measured in m/s^2) */
  Serial.print("\t\tGyro X: ");
  Serial.print(gyro.gyro.x);
  Serial.print(" \tY: ");
  Serial.print(gyro.gyro.y);
  Serial.print(" \tZ: ");
  Serial.print(gyro.gyro.z);
  Serial.println(" radians/s ");
  Serial.println();

  delay(100);

  //  Serial.print(temp.temperature);
  //
  //  Serial.print(",");
  //
  //  Serial.print(accel.acceleration.x);
  //  Serial.print(","); Serial.print(accel.acceleration.y);
  //  Serial.print(","); Serial.print(accel.acceleration.z);
  //
  //  Serial.print(",");
  //  Serial.print(gyro.gyro.x);
  //  Serial.print(","); Serial.print(gyro.gyro.y);
  //  Serial.print(","); Serial.print(gyro.gyro.z);
  //
  //  Serial.print(",");
  //  Serial.print(mag.magnetic.x);
  //  Serial.print(","); Serial.print(mag.magnetic.y);
  //  Serial.print(","); Serial.print(mag.magnetic.z);

  //  Serial.println();
  //
  //  delayMicroseconds(measurement_delay_us);
}

Adafruit library that I used: GitHub - adafruit/Adafruit_ICM20X: Arduino library for ICM20X

Output:

Adafruit ICM20948 test!

ICM20948 Found!

Accelerometer range set to: +-16G

OK

Gyro range set to: 2000 degrees/s

Accelerometer data rate divisor set to: 20

Accelerometer data rate (Hz) is approximately: 53.57

Gyro data rate divisor set to: 10

Gyro data rate (Hz) is approximately: 100.00

Magnetometer data rate set to: Shutdown

		Temperature 30.25 deg C

		Accel X: -0.08 	Y: -0.28 	Z: 9.94 m/s^2

		Mag X: 0.00 	Y: 0.00 	Z: 0.00 uT

		Gyro X: -0.02 	Y: 0.01 	Z: 0.01 radians/s


		Temperature 30.68 deg C

		Accel X: -0.09 	Y: -0.26 	Z: 9.88 m/s^2

		Mag X: 0.00 	Y: 0.00 	Z: 0.00 uT

		Gyro X: -0.02 	Y: 0.01 	Z: 0.01 radians/s

		Temperature 30.68 deg C

		Accel X: -0.10 	Y: -0.26 	Z: 9.86 m/s^2

		Mag X: 0.00 	Y: 0.00 	Z: 0.00 uT

		Gyro X: -0.02 	Y: 0.01 	Z: 0.01 radians/s

		Temperature 30.49 deg C

		Accel X: -0.12 	Y: -0.22 	Z: 9.77 m/s^2

		Mag X: 0.00 	Y: 0.00 	Z: 0.00 uT

		Gyro X: -0.02 	Y: 0.01 	Z: 0.01 radians/s

		Temperature 30.68 deg C

		Accel X: -0.08 	Y: -0.21 	Z: 9.86 m/s^2

		Mag X: 0.00 	Y: 0.00 	Z: 0.00 uT

		Gyro X: -0.02 	Y: 0.01 	Z: 0.01 radians/s

		Temperature 30.39 deg C

		Accel X: -0.10 	Y: -0.29 	Z: 9.84 m/s^2

		Mag X: 0.00 	Y: 0.00 	Z: 0.00 uT

		Gyro X: -0.02 	Y: 0.01 	Z: 0.02 radians/s

		Temperature 30.25 deg C

		Accel X: -0.04 	Y: -0.26 	Z: 9.85 m/s^2

		Mag X: 0.00 	Y: 0.00 	Z: 0.00 uT

		Gyro X: -0.02 	Y: 0.02 	Z: 0.01 radians/s

		Temperature 30.78 deg C

		Accel X: -0.05 	Y: -0.24 	Z: 9.87 m/s^2

		Mag X: 0.00 	Y: 0.00 	Z: 0.00 uT

		Gyro X: -0.02 	Y: 0.01 	Z: 0.01 radians/s

Setup Picture:

jremington · August 10, 2025, 2:05am

The magnetometer is actually a separate chip in the same package, independent of the gyro and accelerometer. It is possible that it was not initialized correctly, or is malfunctioning.

Please follow forum guidelines and post a link to product page for the IMU module, edit your post to remove the screenshot, post the code using code tags, and post a picture of your setup, clearly showing the wiring.

the Adafruit ICM as well as a 3D party ICM from amazon

If you bought a sensor from Adafruit, post on their forum for professional advice. Adafruit supports their products and might even issue a replacement. Be sure to use one or more of the built-in examples from the official Adafruit library to test the setup.

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ICM_20948 Mag Reads 0

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