Airspeed not working when compass +lipo connected


#1

Hello, I’m struggling with a problem on my dropix V1, I noticed that I had intermittent problems with my Airspeed module. So I investigated and here are my findings:

I have a I2C splitter for my compass (which works great) and my digital airspeed from drotek.

When I connect my plane via USB, everything works as expected, however when I plug in the Lipo, my airspeed freezes. If I disconnect the compass it will work again.

When I disconnect the compass and plug in the Lipo, the airspeed keeps working but gives me 5more km/h indicated in Mission Planner.

So there is a combination of a I2C splitter/compass and Lipo powering that makes no sesne to me.

Please note that it does work sometimes (rarely).

I do not have any ferrite on the cable (20cm long) as I believe it doesn’t matter much on a digital sensor.

Also to be noted that in Mission Planner, the checkbox for activating airspeed is greyed out, the use airspeed is worlking and enabled however.

Thanks for your help


#2

Check if the voltage on the I2C splitter is different when powered by the Lipo.


#3

Hi, it is different indeed: 4,56V on USB and 4,87V when I plug the Lipo.
I also checked the signal voltages if that matters and they are the same in both cases.

Could it be it ? In both case voltages are within the limits.

Thanks for your help


#4

Hi, there is some news, now it doesn’t work even on USB, it’s really a matter of I2C adress or something since the airspeed alone on the splitter with compass DISCONNECTED works well. as soon as the compass is connected it’s not working anymore. Sometimes plugging the lipo makes things worse sometime not.

I erased and reflashed the software several times, also the checkbox in mission planner for the airspeed is greyed out even after reinstall so I am considering a hardware default !