BerryGPS-IMU compass “north”

[currydem]

I have a simple question. I’ve searched and found two separate answers. Which side of the BerryGPS-IMU is the “north” side. Like which side is facing towards the heading to be read? The short side with the “ublox” chip (Red arrow) or the long side next to the antenna switch (Blue arrow)?

 

 

 

Attachments:

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   IMG_7607.jpg
   

[Mark Williams]

It is the blue arrow
On the next version, we will place an indicator on the PCB

Mark --OzzMaker.com --

[currydem]

Thank you so much I have another question about the C files used in the tutorial and the python file. Would it be appropriate to ask it in this same thread or should I make another with that specific topic?

[Mark Williams]

no.. go ahead here if you like

Mark --OzzMaker.com --

[currydem]

In the tutorial for the compass it is written in C and it has a section to compensate for soft iron distortion as well as magnetic declination. In the Python compass code it does not. I tried to mimic a soft iron distortion section but when I do this it doesn’t give me the correct heading. I also get a different heading (an incorrect one) when I use the original Python compass code even after calibration

 

code below:

 

Hard iron distortion

 

C code

magRaw[0] -= (magXmin + magXmax) /2 ;

magRaw[1] -= (magYmin + magYmax) /2 ;

magRaw[2] -= (magZmin + magZmax) /2

 

Python code

 

MAGx -= (magXmin + magXmax) /2

MAGy -= (magYmin + magYmax) /2

MAGz -= (magZmin + magZmax) /2

 

 

 

Soft iron distortion

 

 

 

C code

 

scaledMag[0]  = (float)(magRaw[0] – magXmin) / (magXmax – magXmin) * 2 – 1

scaledMag[1]  = (float)(magRaw[1] – magYmin) / (magYmax – magYmin) * 2 – 1

scaledMag[2]  = (float)(magRaw[2] – magZmin) / (magZmax – magZmin) * 2 – 1

 

Python code (what I tried to adapt to the Python code)

 

scaledMagX  = (MAGx – magXmin) / (magXmax – magXmin) * 2 – 1

scaledMagY = (MAGy – magYmin) / (magYmax – magYmin) * 2 – 1

scaledMagZ  = (MAGz – magZmin) / (magZmax – magZmin) * 2 – 1

 

 

 

 

C code

float heading = 180 * atan2(scaledMag[1],scaledMag[0])/M_PI

 

Python code (what I tried to adapt to the Python code)

 

float heading = 180 * atan2(scaledMagY,scaledMagX)/M_PI

 

*****original code*********

heading = 180 * math.atan2(MAGy,MAGx)/M_P

***************************

 

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