ArduRover 4.2 NEO M8N - GPS: NO FIX and Unhealthy AHRS


I have been trying to connect a Ublox NEO M8N GPS to ArduRover 4.2 on my Pixhawk 2.4.8 with Mission Planner v 1.3 as the GCS. Every time I try to turn on the rover, I get the message “GPS: NO FIX” and “Warning: Unhealthy AHRS”. I’ve recalibrated more than once, used more than one of the same model… but I receive the same message every time. I even took it out to a field on a sunny day with clear skies to no avail. What could be wrong? The LED on the GPS also always remains red, I never see a blue light like a correct connection would show. Here is the parameter file:
ugv-param.param (14.3 KB)

Could there be any alternatives to using GPS for Auto mode using Rover? I have some rangefinders that can interface with the Pixhawk as well that may be able to do the Job. Thanks!

The connection doesn’t change the behavior of the LED detection of Sats does.

Oh I misspoke. To be clear it is connected and powered. From what I’ve read “no fix” means there’s no Satellite detection like you said. I cannot for the life of me figure out why however.

Usually you let them sit long enough to an open sky and they will find satellites. Try setting GPS_GNNS_MODE to 65 and reboot. This depends on where you are but GPS+GLONASS works just about everywhere.

Thank you! I will try this. Those parameters were previously set to zero. Would that mean it’s didn’t have any mode set up?

Also sorry for so many questions, but does it need to be a sunny sky with no clouds in an open field to work, or will it at least increase my chances? I’ve tried it before in a cloudy sky without success, but I also took it out to my apartment’s courtyard on a sunny day and a nearby park on a sunny day with no luck either time.

No, just whatever defaults were on the module. This usually will work fine so setting these specifically may not help.

No, in fact it’s typical to get some Sats inside. I do bench work all them time and always have some Sats.

Strange. Ive never seen sats indoors or out. Does that indicate i have a defective model?

Can you post a pic? repositioning the GPS away from the telemetry may help.

Here is an image.

I also have a mount I can use to increase distance between GPS and Telem. Though that didn’t seem to make a difference.

Please note only essential components are on so that Lidar module and other peripherals are off.

I would say they are too close.

Is the TX antenna wire under the GPS?

Yes, for the remote control’s receiver. I moved it away now and also elevated the GPS.

GPS has a weak RF signal, very susceptible to noise from other RF transmitters. Keep it away from everything & shield the GPS with alloy (a tin lid or cut soda can) I hope that helps.

If that’s a Pi board is it powered and what’s connected to it?

Yes it is a pi. For right now it is not powered. I was thinking of using SLAM with that Lidar for autonomous navigation using the Pi but it is not set up yet.

Right, so would I only cover the bottom and sides of the GPS and leave the top open?

Yes I should have mentioned that!

I don’t know, I have a few small quads with the GPS module packed in pretty tight and I don’t have GPS reception problems. On my Rover I have 915Mhz RC, 915Mhz telemetry and a WiFi radio on a vehicle about that size and I don’t have a problem with that either. You can try foil but I have never had to use it.

Got another GPS module to try?

Thank you for your help. I’ve ordered one: the Matek M8Q-5883. I’ve read it’s reliable, Hopefully it solves my issue. Meanwhile I’m looking into other ways to achieve autonomous navigation.