Replies to This Discussion

DeveloperPermalink Reply by Randy on December 14, 2010 at 5:13pm

Yes, I believe you are correct.  You're not the first one to find this problem but you are the first one to illustrate it with a picture so clearly!  It's up to Jordi to fix this one on an upcoming batch.

 

Of course I don't know exactly how you're using the compasses, but if you're using Arduino + the AP_Compass library then the orientation can be set with the set_orientation call and there are a bunch of predefined constants for both boards which makes it easy to get it working properly.

 

https://code.google.com/p/arducopter/source/browse/#svn/trunk/libra...

https://code.google.com/p/arducopter/source/browse/trunk/libraries/...

• ▶ Reply

Permalink Reply by Uwe Gartmann on December 14, 2010 at 5:58pm

Hi Randy,

 

I watch the code very close :-)

 

 Honestly, the code for the magnetometer has never been official released yet. There is more than just a readout from the adc.

 

Can somebody explain me why the X and Z axis in the AP_Compass_HMC5843.cpp has different Signs (-)?

  {
    // MSB byte first, then LSB, X,Y,Z
    mag_x = -((((int)buff[0]) 8) | buff[1]) * calibration[0];    // X axis
    mag_y = ((((int)buff[2]) 8) | buff[3]) * calibration[1];    // Y axis
    mag_z = -((((int)buff[4]) 8) | buff[5]) * calibration[2];    // Z axis
    last_update = millis();  // record time of update
  }



Is this not covered by the declaration of the orentiation of the sensor?

 

 

• ▶ Reply

Permalink Reply by Fabio Varesano on December 14, 2010 at 7:03pm

They are probably aligning the HMC5843 axis to those of the accelerometer and gyro.

 

Negating X and Z is like making a 180deg rotation around the HMC5843 Y axis.

• ▶ Reply

Permalink Reply by Uwe Gartmann on December 15, 2010 at 4:06am

Ok, I see.  It corrects wrong axis when you mount the board direct on the shield (see wiki).

 

• ▶ Reply

DeveloperPermalink Reply by Randy on December 15, 2010 at 4:47pm

ok - good point about being able to use the orientation instead of the -ve on x & y.  Nothing's broken but perhaps it's unnecessarily confusing.

 

I'll give that a go (unless someone else wants to fix it an send me the changes!).

• ▶ Reply

3D RoboticsPermalink Reply by Chris Anderson on December 15, 2010 at 1:44pm

Jordi is aware of this cosmetic issue and will correct in the next version.

• ▶ Reply

Permalink Reply by Uwe Gartmann on December 15, 2010 at 3:51pm

Perfect.

Please put a small note to the current documentation.

• ▶ Reply

3D RoboticsPermalink Reply by Chris Anderson on December 15, 2010 at 4:18pm

Done

• ▶ Reply

Permalink Reply by Darren on December 15, 2010 at 3:58pm

Please note, you have v1.1 pic which is also different from the previous ver. which I have that has two removable sides. (4 holes)

 

Also, did you notice that your right hand digram is inverted? Also in that diagram is an X vs. a Dot which indicates out rather than in... or up vs down I believe.

• ▶ Reply

Permalink Reply by Luis Mauro on January 2, 2011 at 6:51pm

Hello dears

I would like to report a problem that I'm having with the HCM5843 from DIY Drones.
I connected the HCM5843 board to Arduino´s Duelmilanove I2C (pins A4=SDA and A5=SCL). The code that I´m using is copy from ArduIMU ("Compass").
When I turn on the Arduino and the HCM5843 boards, everything works good, but after ~30 seconds the heading value become crazy (oscillating to much). The HCM5843 and Arduino both are working with 5V.
The problem I described above is similar to the reported by Fabio Varesano on the Arduino forum: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1291403700
Pull-up resistors: I've tried no pull-up resistor and values of 10K, 3.3K 4.7K and it works stable for a little more time with high values pull-up resistors.

• ▶ Reply

3D RoboticsPermalink Reply by Chris Anderson on January 2, 2011 at 7:10pm

Luis, I'm not sure our libraries will work on regular Arduino boards. We don't see any problems with the magnetometer on APM boards.

• ▶ Reply

Permalink Reply by Luis Mauro on January 2, 2011 at 7:44pm

Hello Chris

Thank you for your reply. I´m using the wire.h library (Arduino's regular library).

The code is attached (Compass.txt) that is a modified copy from ArduIMU code (by Jordi Munoz and William Premerlani, Supported by Chris Anderson (Wired) and Nathan Sindle (SparkFun).

I only made small modifcations to run the code alone and no tilt compensated.

During the test I keep HCM5843 board with roll and pitch angles equal to zero and fixed yaw (no movement, static).

I took this board (http://store.diydrones.com/HMC5843_Triple_Axis_Magnetometer_p/br-hm...) because it works with 5V devices, I believe that no level conversion is necessary.

 

Attachments:

• Compass.txt, 3 KB

• ▶ Reply

• ‹ Previous
• 1
• 2
• 3
• 4
• Next ›
• Page