I2C External Compass (uBlox MAG) Issue

Archive
1

Symptom: I2C components not recognised with MAG connected.
Compass, Airspeed & External LED
Fault finding attempted
Empty I2C board test for continuity – good
Connected LED – good
Connected Airspeed sensor – good
Normal indications at Pixhawk (External LED lit)
Mission planner shows readout.
Connected MAG – all I2C data missing (Internal LED lit)
Voltage present on I2C board at all connected ports (all ports connected at some point)
Software 3.2.3
Tried previous software – same result
When running the wizard neither compass is present with MAG connected. With MAG disconnected the internal compass is recognised.
Tried 2 separate Pixhawk, 2 I2C and 2 uBlox setups – same result.
Can anyone help?

2

@Bruce_ITPS,
Are you using a genuine 3DR GPS/Compass or is it a clone or other brand?
Regards,
TCIII GM

3

All genuine, that is all sourced from 3DR. It is holding up the Anaconda build.

4

@Bruce_ITPS,
I have alerted our ArduPlane Developer to your issue.
Regards,
TCIII GM

5

OK, the problem is fixed, kinda.

I checked over the config files I use and found that they had changed; Pixhawk was no longer detecting the external compass.
I reviewed the settings in the Aero RTF config file and put those settings in my own config files - no joy.
I uploaded the Aero RTF config and everything worked.
I then uploaded my own config files and everything worked (classic IT solution #1 - turn it off and turn it on again).

However, I am still at a loss why MAG auto detect disabled should affect the whole I2C bus or why my config was rejected then accepted purely by loading a different file.

Thanks for your patience.

6

Hi Bruce. I2C is yucky. Its designed for internal chip communication, not to external components. And being a bus architecture any single component on the bus with issues will impact all the others.
The pixhawk configuration by default will auto detect the external compass and use that as the primary. Not sure what was happening with yours. If it happens again please send a log through and we will have a look.
Can’t wait to see the Anaconda.
Thanks, Grant.

7

Understood. And thanks.