"need 3d Fix" issue - SOLVED!

Cube Autopilot
#1

hi
I need a little info. After moving the FC from one frame to another (identical) and after a reset, the FC Cube Black always gives me the same error: “need 3D fix” even if the acquired satellites are 17
The system is a Cube Black with Herelink and GPS Here2 (connected in Can). I have disabled compasses 1 and 2 (internal) and I have active only 3 (external) and HDOP 0,7 (limit fix at 2,5)
I left the system in the middle of a field for 1 hour to give time to enumerate the constellations and calibrated the compass 3 several times but the problem remains

another small detail … if I enable compass 1 (internal) and 3 (external) the problem disappears but the UAV works very badly … hovering with “toilet” effect and deviation of course in a straight way … etc ( probably suffers from some EM field due to the DB that is in the area and it is for this reason that I want to use only the external one)

For all of the above, do you have any advice on how to solve the “need 3D fix” problem?

#2

Reset to default values in full parameter list.
Redo calibrations
Go out in the open and do the compass calibration
It will solve this issue

#3

Thanks Delta1 for the reply

I did a lot of tests and I didn’t understand if it was due to my inexperience or because it is a very popular topic, quite frequent but the solutions are among the most varied.

I bring my experience here

“NEED GPS FIX” SOLVED!

I don’t know if the architecture of the algorithms are exactly as I am describing them (they are guesses) but this is the solution I found and it works on my system which is made up as follows:

-CUBE Black 2.1 with Herelink and Here V2 and use of external compass
-Mission Planner Ver. 1.3.74 and ArduCopter V4.0.6

My problem was to always have the message “need GPS Fix” while acquiring 16/17 satellites

The problem was related to the fact that I had disabled Compass 1 and 2 and the flag was on Compass 3 … also using Here 2 in CanBus I had compass 3 which was third in the list at the top of the “Compass” page (so. … internal (1), internal (2), EXTERNAL (3))

It was enough to do 2 things:

  1. Compass 3 switch from position 3 to position 1
  2. close MissionPlanner
  3. open QGC and click: Sensor -> Sensor setting and select on "Compass 1 (external) -> Use Compass 1 [priority1]

end

The system now recognizes the GPS and uses it correctly

In practice it is not enough to leave the external compass as “Compass 3 (external)” in the check boxes at the center of the page, but it is necessary to move it to Compass 1 position and assign Priority 1 with the procedure described above

I don’t know if this procedure is the most correct but it is the one that allowed me to get out of the problem

Thank you all

#4

Great to know that buddy
Happy landings :blush::+1:

#5

Also check you’ve got BRD BOOT DELAY set to something like 5000 when using CAN devices.
Also update to latest stable release if not already.