AP: Internal Errors 0x800000 (stack_overflow) on speedybeef4v4 with signing and eLRS RC on ArduCopter 4.6.3/master

[Jaaaky]

Bug report

Issue details

On v4.6.3 or master build a firmware as

./waf distclean; git submodule update --init --recursive && ./waf configure --disable-scripting --board=speedybeef4v4 && ./waf -p copter && uploader.py build/speedybeef4v4/bin/arducopter.apj

After boot, connect to mavproxy, enable signing, connect eLRS RC

1. When both mavproxy and eLRS TX are on/connected it fails to complete the boot process showing AP: Internal Errors 0x800000 sometimes, sometimes print "stack overflow" and sometimes simply stuck at random boot stage usually after RCInput: decoding CRSF message.
2. When either mavproxy or eLRS RC are connected but not both the boot process completes fine, you can later connect/turn on both no problem.

Version
master / 4.6.3 stable

Platform
[ ] All
[ ] AntennaTracker
[ x ] Copter
[ ] Plane
[ ] Rover
[ ] Submarine

I could reproduce the bug only on ArduCopter not on ardoplane or ardurover firmware.

Airframe type
N/A

Hardware type
What autopilot hardware was used? (Pixhawk, Cube, Pixracer, Navio2, etc)
speedybeef4v4

Logs
Please provide a link to any relevant logs that show the issue

[anshul23102]

Thanks for the detailed report. I’m interested in looking into this.

Given that it only happens on ArduCopter, during early boot, and only when MAVLink signing + CRSF (ELRS) are both active, this feels like a stack or init-order interaction between MAVLink and RCInput.

I’ll try to reproduce this on a SpeedyBee F4 V4 with the same build flags and see where the failure occurs. Happy to take this on if useful.