"Hi Bill,
I also read the documentation for the HMC5843 but could not find any I2C commands for the S/R straps.

But if you look at the pins of the sensor you recognize that you have the the SETN pin available to you. This pin with SETP could be used…"

"Hi Bill,

In the source code I couldn't exactly find where tau is found and what value you have chosen for it. Could you please tell me which line it is in?

Regards
Dave"

"Hi Bill,

I appreciate your help also. You are always inspiring us.


Can you please tell me how did youknow that the loop gain is (3 - Trace(R21))/tau) and why is the loop gain the inverse of tau?

Regards
Dave"

"Hi Bill,

Sorry, you should find the answer on page 6. The principal is easy. Whenever you apply a reset pulse to the strap the magnetometer will function with negative sensitivity the rest of the time.

If you apply a set pulse vice versa is true.…"

"Hi Bill,

Two small questions:
1) How does equation 11 solve the problem in issue 1.
2) Do you mean that the denominator is the same as tau.

Please explain with some detail. I appreciate it.

Dave"

"Hi Bill,
Please see the document : AN212 "Hnadling Sensor Bridge Offset" page. 5

The method is simple. Suppose that the ambient magnetic field is -127mG.

Now if you apply a set pulse to S/R strap you will have a reading of: -127mG + offset

Now if…"

"Hi Bill,

In your equation (8) you have an "exact formula" for the offset in the plane perpendicular to the rotation
axis. You use instead the variable vector: the numerator of that equation. In equation (11) you update
the offset estimation by…"

"Hi Bill,

Why didn't you use the set/reset straps of the magnetometer. You could easily find the offset voltage by a simple algebraic sum of two samples?
Dave"