BMM150 problem

[Migrant_worker]

HI，

I used the X-axis and Y-axis data obtained from the BMM150 to perform the following operations

compass = atan2f(mag_mx,mag_my);
if(compass < 0)
{
compass+= 2 * PI;
}
if(compass > 2 * PI)
{
compass-= 2 * PI;
}
TCompass = compass * 180 / PI;

When the X-axis points north I get zero degrees, and I can rotate it to get an Angle from 0 to 360

But as I move horizontally toward the north, my Angle slowly increases. Is that normal? What causes it? How do I fix it?

[BSTRobin]

Hi Migrant_worker,

Do you mean you move horizontally toward the north, the angle of the compass increase?

[Migrant_worker]

HI,

Yes,

moving horizontally to the north increases the Angle of the compass.

What is the cause of this phenomenon?

What can be done about it?

[BSTRobin]

Hi Migrant_worker,

Moving BMM150 horizontally will cause a change in the compass reading. In theory, this is normal because the position of the device has already changed.
Individual BMM150 data cannot obtain the angle of the compass, and a fusion algorithm needs to be run in conjunction with IMU data to obtain the compass data.