GPS Glitching after plugging in usb cable from Raspberry pi 4

Hi, we have got a strange GPS glitch issue while using arducopter. Version: V4.0.3, Hardware: Pixhawk. As soon as we connect raspberry pi 4 ( 8gb variant ) to pixhawk using usb, the GPS Hdop keeps fluctuating at higher values over 1 and constant GPS Glitching message keeps appearing. When we remove and fly it normally in stabilize,loiter modes, no such issues occured.
Log file can be found here -> log_files.
Is there a way to sort this issue?

USB signals interfere with GPS signals. Keep USB cables away fro the GPS Antenna.

Hi @amilcarlucas thanks for the reply. But we flew it several times the same way and never got such issue. The difference this time was BEC (to raspberry pi ) was giving 6v output (due to faulty jumper connection) and changed it back to 5v. after that it keeps giving glitching issue. could there be fault on raspberry pi ? any way to diagnose it?

Google for “USB interference in GPS” and come back to us.

I had problems with EMI in the past with bad UBECs and dc/dc converters, you can use an oscilloscope to see if when you plug it to the RPI, a close wire is interfered with EMI, for example a GPS wire. If you see fluctuations when you connect it or not, then that is your problem. Furthermore is known that USB interfere with GPS signal (as amilcarlucas told you), specially USB 3.0.

@amilcarlucas, @davidae thanks for your inputs. Yes, The USB 3.0 has interference issues contributing to +/- 20db signal noise. as far as proximity and amperes the devices are drawing is concerned the interference is eliminated/ignored. one point that @Haneesh_Allu forgot to mention is "SD CARD GOT CORRUPTED On 6V Power and also 6v was supplied from raspi GPIO pins. (P.S we are new to power electronics :-p)

we have run some tests today and after going through raspi forums we got to know in a hard way that. GPIO pins are meant to 5v output rather than giving 5v input to the board. since they are directly routed to SOC and they don’t have any protection against incoming voltage fluctuations. instead, people advised using a micro-USB port which got a Zener diode as a fuse for protection against voltage fluctuations.

We also faced runtime errors due to memory leak and USB adapter getting shutdown with the program suddenly announcing “device not found” errors which we point out to the processor getting damaged.
we just ordered a new raspi4 and we will run similar tests to further pinpoint the problem.

Thanks for your help.