Outputs occasionally lockup after a GPS fix at the moment of arming

[rts18]

This is a condition I've been meaning to report for a while. It isn't anything new. But is common enough to be frustrating when you arm and are about to launch.

From my years of observing this problem I have seen the servos jitter a very small amount the moment a 3D fix is acquired.
This apparent activation of the AHRS. Which seems to lead to the slight servo jitter. Is always followed by the servos and motor/s becoming unresponsive after the FC is armed. But the servos would respond to a stick command before the 3D fix and arming.

The only way I find to deal with this is to :

• Arm and disarm before the 3D fix.
• Power cycle the FC after it occurs.

It doesn't happen every boot. But it happens frequently enough to be significant with H743 and F765 wing boards. I have not encountered it on a multicopter flight controller.
I haven't seen any other reports of this problem. But surely I can't be the only person who has experienced it hundreds of times over the last few years, depending on how much you fly. Unless it's linked to the use of certain settings.

[sensei-hacker]

Got a diff? Also, which flight mode have you been in when you noticed this?

[rts18]

This airplanes diff isn't too complicated. But it still experiences the problem now and then.
To explain how often this takes place. I would say 2 times in every 30 flights. Which isn't very often. But if you're a person like me who fly's more than one hundred times a year. The occurrence of these events becomes more memorable over that course of time.

It could have occurred in Acro mode once or twice. But most of the time it would be in Angle mode waiting to activate fixedwing auto launch.

INAV_9.0.0_cli.txt

I'm not expecting its cause will be easy to track down. Maybe not even using the STIL. Thanks for your interest @sensei-hacker

[sensei-hacker]

A few more questions:

You mentioned the servos become unresponsive.
Do you fly with an OSD? I'm curious if it also stops responding. I'm wondering whether it's a servo handling problem, or a "the FC completely locks up" problem.

Also, do you use blackbox?

I've noticed something lately. F765 MCUs aren't that common - except in bug reports? They seem to maybe have more than their fair share of bug reports, perhaps.
You mentioned "H743 and F765"; are you pretty confident you've seen this issue on both H743 and F765?

[rts18]

Do you fly with an OSD? I'm curious if it also stops responding. I'm wondering whether it's a servo handling problem, or a "the FC completely locks up" problem.

It's not often I have the DVR recording before arming. So it's hard to remember.
When it does take place I just unplug the battery and go again.
But thinking back to a few days ago when it occurred. I remember the OSD was blinking. But when I disarmed the post flight stats didn't appear on the OSD. That could mean the flight controller had locked up and not just the PWM outputs.

That airplane was using an F765.
I use blackbox. I only log at 32 after reading of possible issues when logging faster.

are you pretty confident you've seen this issue on both H743 and F765?

Yes both. I have three airplanes with F765 and five with H743.
Thinking long and hard of the planes I've seen this happen with. I'd say it's a more common occurrence on the ones with F765 FCs.