GPS doesn't fix if Pi is powered on with RF USB module attached

Navio / Edge Hardware
1

Hi

I’m using a Navio2 with a Pi2 with image: emlid-raspbian-20160718.img and ArduPlane V3.7.12

When I power on the Pi/Navio2 without my RF USB Module and start ArduPlane like this:

sudo ArduPlane -A udp:192.168.1.136:14550

Everything is fine.

If I power on with the RF USB Module and start like this:

sudo ArduPlane -C /dev/ttyUSB0 -A /dev/null

I never get any GPS Fix og sats?

But if I attach the USB RF after power on I sometimes will get a GPS Fix.

rf.jpg3264×2448 1.05 MB

2

I have exactly the same issue with my rover and a Navio2. I have different sets of 3DR and clone 433MHz transceivers and they all interfere with the GPS. The older Hobbyking modules even affect the steering servo. It starts to twitch and pulse as soon as I plug the module into the USB port. If I use a cord and move the module around, the twitching varies in strength.
I use those modules without a problem in my pixhawk controlled copter and a pixfalcon controlled Twinstar. The copter has a Ublox 6 GPS and the Twinstar the M8N GNSS that came with the pixfalcon.

3

i have a cheap 3dr clone 433, i did not notice a big difference on Navio’s gps, but I did not get any sats when using a similar 3DR clone 433 on an old APM2.8 with a neo7m when placing antenna really near to the gps;
i will test that on the weekend;
if i had those problems i would solder some capacitors to the 3dr GND/5V+ and observe if the (high frequency) power peaks from the 3DR modem irritate the ublox gps chip from the rpi usb power lines; (because @schuermannsebastian says they work fine on his pixhawk)
otherwise just distance between 3DR and GPS or maybe shielding would help…

4

The weird thing is that if i attach the RF after having got a fix, and then restart ArduPilot I’m able to get GPS fix, but then my accel/gyros become unstable (unstable horizon)

5

are you using your gps antenna in an open area? because inside/near buildings you will not have good gps reception;

6

I’m on the top floor of the building. Tomorrow I will try outside.

How would I go about trying to shield the RF module?

7

copper or aluminium foil is an adaequate choice to shield from hf interference!

8

I tried covering the RF module in aluminium foil which stops the interference from being audible in my speakers, but still if I power on the RPi with the RF module attached I get no GPS Fix.

If I power on with the RF module physically detached, start APM and wait for GPS Fix and then stop APM, attach the RF module and start APM I am then able to get a GPS Fix??

9

what’s the gps status when you don’t get a fix? 0, 1 or 2?

10

GPS Fix () is 1
and
GPS Sats () is 0

edit:

and
GPS COG () is 0

edit:

Another bit of weirdness, if I stop and start APM to many times, I’ll get GPS Fix, but the accel/gyro is all over the place (very unstable horizon) ??

11

Take a look at this post, please!

12

The GPS antenna connector seems pretty tight. Theres really no wiggle room. All I can do is rotate around the axis.

Also I have no instability issues with GPS unless the RF Module is powered on.

13

Could run the examples? Also it seems like there’s interference with the radio. I suggest you to use another one.

14

I was trying to order a set direct from 3dr, but they charge 90$ in shipping for international orders.

Then I found this: http://www.banggood.com/500mW-3DR-Radio-Telemetry-AirGround-Module-433MHz-915-MHz-For-MWC-APM-PIXHAWK-Pirate-p-982005.html?rmmds=search

But I’m not sure if its original 3dr?

Looks a lot like the ones I already have from hobbyking.

15

I placed the Navio2/RPi in a small faraday cage and the problem is gone.

Hope that the new RF set I ordered will work better.

Thanks to all for your replies .