I’m having issues with getting a RTK fix on a homemade quadcopter.
Hardware is the following :
Drone : Pixhawk 6C mini, Holybro H-RTK NEO-F9P w/ Helical Antenna.
Connected via the GPS 1 port on the 6C
ESP32-C3 with DroneBridge for the telemetry Mavlink.
Base : H-RTK NEO-F9P w/ Base Station Antenna
Connected via USB to the computer.
2.4GHz router for the telemetry Mavlink.
Except from not getting a RTK fix, everything is perfectly working, including the telemetry which was thouroughly tested with manual commands from Mission Planner and direct joystick input via USB.
Yet, when injecting the RTK/GPS after a 1m precision survey, the drone seems to be stuck in 3D Fix mode.
As for the config, GPS1 was tester both in 1 (auto) and 2 (uBlox) mode, and doesn’t affect the results.
Appart from that, telemetry link is using 115200baud rate.
It’s also important to note that I get the error message : “Configuration of fixed position on Septentrio receiver failed.” but it’s irrelevant in my case, because not using Septentrio and this is a known bug : Configuration of fixed position on Septentrio receiver failed
Even after long waits for an RTK Fix, nothing happens.
Could this be a problem on the telemetry side?
The other problem is that I can’t find a way of seeing the telemetry corrections go through via Mavlink, to ensure that they are actually transmitted.
It is possible that the onboard ublox is not configured to expect the rtcm messages at all, otherwise it would attempt an RTK Float solution, and would report as much. That, or the two receivers don’t see the same sky, which is unlikely but possibly a misconfiguration.
Did you configure the ublox manually, or with the autopilot gps auto-config workflow?
GPS auto config was always enabled in my ardupilot params.
I did a little more digging and connected via U-center in USB to my Drone while the wifi link is active with the base station connected to the computer. In the MSGPP from the MONitor section (UBX) i see that protocol 5, RTCM3 increases with time on UART1.
But a problem I noticed is that altough the GPS receiver on the drone works fine for himself with the 3D fix, in the RTCM3 messages view 1005 RTK Base station is grayed out.
So no correction actually gets to the Drones F9P module.
Yet, also on the Base, from Mission planner we can see the output data rate non equals to zero meaning correction is beeing sent.
I also include my parameter list here. (Note that I use Skybrush Arducopter firmware for the Pixhawk 6C, but I have the same RTK problems with Copter v4.5.7 firmware)
This is good but there’s more to the story. There’s a section somewhere in there that tells you exactly which RTCM messages you’re receiving. There’s a status message that will go out no matter what, but there are also satellite correction messages unique to each satellite that you should also be expecting in order to fully calculate a solution. It will take me some time to reproduce the setup locally, but with that information you might be able to find it yourself.
Seeing the status message but no satellite messages can be reproduced by taking a working setup and covering the antenna for the base station or the moving baseline “base” receiver. You’ll see the individual correction messages drop off while seeing the status messages come through. An ESD bag will produce stronger results (the gray metallic ones, not the pink anti-static material), or usually removing the antenna and covering the cable with your hand, it should be a noticeable difference.
In the above case, even though RTCM status messages are being sent, the rover will not be able to calculate even an RTK Float solution.
Indeed it was a misconfiguration on u-center from the Drone GPS module. After a full reset everything is in order.
Thanks for helping !
I just want to test out the fact that it was maybe misconfigured from Holybro, because I’m almost certain that I did not modified any params on the Drone F9P, only on the Base Station F9P.
I will soon receive a new batch of Holybro Neo f9p for additionnal drones. I will mention it if I find any out of the box misconfig that leads to the problem I was having.
Thanks again from both of you !
