Lost power on current main power brick causing the avionic reboot

[hitagisol]

I notice that in the case when multiple power bricks present, if the current main power source failed the avionic will reboot.
Here is the test I've made on Pixhawk 5X:

• Hardware setup: Connect Power 1, Power 2, USB as power source, Power 1 and Power 2 come from the Holybro PM03D module and the USB comes from my laptop.
• Test procedure:
  1. Remove the connector from Power 1, while the Power 2 and USB remains connected, the avionic goes into the reboot routine.
  2. Remove the connector from Power 2 while the Power 1 and USB remains connected, the avionic keeps working without reboot.
  3. Remove the connector from Power 1, trigger the avionic goes into reboot. After the reboot, remove the connector from Power 2, the avionic reboots again.
     Right now I'm assuming this is caused by the path switch handled by the LTC4417 controller, but I have no idea what test I can perform to prove that.

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Test update:
I made some further test with the power issue:
Test 1: Apply a 1000uF capacitor on the Power 1 port trying to act as a "backup power" during the Power 1 disconnetiong period. But it does not change anything.
Test 2: Provide power ONLY on the Power 1 port with a variable power source. The idea of this test is to understand at which voltage the avionic will fail. I notice that when the input power drops to 4.0V the Pixhawk 5x board switched off. According to the DS-010 Pixhawk Autopilot Bus Standard, the power path switch will happen at 3.8V. So I'm affraid the avoinic is already switched off even before the power path is switched. That is why the external capacitor can not help.

[hitagisol]

@LorenzMeier I'm sorry for the manually ping but since this repo is not so popular I don't know if there is someone taking issues here periodically.

[davids5]

@hitagisol Have you verified this on more than one FMU?

[hitagisol]

@davids5 I have the same results on two different Pixhawk 5x. On the Pixhawk 4 board I do not have this issue. Currently I only have these three board in my hand.

[vincentpoont2]

@hitagisol May I ask where you purchase this unit from? I have also sent you an email. Please check.