MMC5983 issues

Qwiic System
1

Hi All,

Anyone managed to get this compass working with the Sparkfun library?

https://github.com/sparkfun/SparkFun_MM … tester.ino

Tried a few of the i2c examples with no success. Heading output ranges from about 140 to 210 degrees in all the examples I tried.

I’m using a Teensy 3.2.

Haven’t had time to fault find yet. Just seeing if anyone had success with the library?

Paul.

Code from compass example -

/*
  Compute magnetic heading from the MMC5983MA
  By: Nathan Seidle and Ricardo Ramos
  SparkFun Electronics
  Date: April 14th, 2022
  License: SparkFun code, firmware, and software is released under the MIT License(http://opensource.org/licenses/MIT).

  Feel like supporting our work? Buy a board from SparkFun!
  https://www.sparkfun.com/products/19034

  This example demonstrates how to compute the heading based on the basic X/Y/Z readings from the sensor over Qwiic

  Hardware Connections:
  Plug a Qwiic cable into the sensor and a RedBoard
  If you don't have a platform with a Qwiic connection use the SparkFun Qwiic Breadboard Jumper
  (https://www.sparkfun.com/products/17912) Open the serial monitor at 115200 baud to see the output
*/

#include <Wire.h>

#include <SparkFun_MMC5983MA_Arduino_Library.h> //Click here to get the library: http://librarymanager/All#SparkFun_MMC5983MA

SFE_MMC5983MA myMag;

void setup()
{
    Serial.begin(115200);
    Serial.println("MMC5983MA Example");

    Wire.begin();

    if (myMag.begin() == false)
    {
        Serial.println("MMC5983MA did not respond - check your wiring. Freezing.");
        while (true)
            ;
    }

    myMag.softReset();

    Serial.println("MMC5983MA connected");
}

void loop()
{
    uint32_t rawValueX = 0;
    uint32_t rawValueY = 0;
    uint32_t rawValueZ = 0;
    double scaledX = 0;
    double scaledY = 0;
    double scaledZ = 0;
    double heading = 0;

    // Read all three channels simultaneously
    myMag.getMeasurementXYZ(&rawValueX, &rawValueY, &rawValueZ);

    // The magnetic field values are 18-bit unsigned. The _approximate_ zero (mid) point is 2^17 (131072).
    // Here we scale each field to +/- 1.0 to make it easier to calculate an approximate heading.
    //
    // Please note: to properly correct and calibrate the X, Y and Z channels, you need to determine true
    // offsets (zero points) and scale factors (gains) for all three channels. Futher details can be found at:
    // https://thecavepearlproject.org/2015/05/22/calibrating-any-compass-or-accelerometer-for-arduino/
    scaledX = (double)rawValueX - 131072.0;
    scaledX /= 131072.0;

    scaledY = (double)rawValueY - 131072.0;
    scaledY /= 131072.0;

    scaledZ = (double)rawValueZ - 131072.0;
    scaledZ /= 131072.0;

    // Magnetic north is oriented with the Y axis
    // Convert the X and Y fields into heading using atan2 (Arc Tangent 2)
    heading = atan2(scaledX, 0 - scaledY);

    // atan2 returns a value between +PI and -PI
    // Convert to degrees
    heading /= PI;
    heading *= 180;
    heading += 180;

    Serial.print("Heading: ");
    Serial.println(heading, 1);
    delay(100);
}
2

Have you followed the link inside the code to set the offsets & scaling factors for the axes? https://thecavepearlproject.org/2015/05 … r-arduino/

Also make sure it’s flat during boot. Circle back if it doesn’t help things along :slight_smile: