I have a weird problem where my receiver (an FS-IA6B) fails to connect with my transmitter on startup 90% of the time but only if my ESC is connected.
After a bit of troubleshooting I’ve discovered what appears to be a design flaw in the Pixhawk redundant power system. What seems to be happening is that the main power bus will oscillate for about 220ms on startup if the BEC power from my ESC is connected to the servo bus.
The yellow trace below is the BEC which comes up cleanly, the red is the main bus which seems to be dropping in and out initially before it settles:
That is very interesting indeed. Just to get a complete picture, are you powering pixhawk via the power module and then via a second BEC on the servo rail for power redundancy, or just via a BEC only?
I have not encountered this before and I am not an expert on the pure electronics side of things (I come from software background) One issue to consider is that are you using a separate BEC, or one from an ESC, if if from an ESC are you only using one? The second issue is that is it a switching BEC/ Linear BEC as I konw switching BECs can cause some issues if more than one are used.
As for your workaround, I am sure this will not be a massive issue as in general R/C receivers are designed to connect directly to same power as sevos/motors so I imagine they will handle this just fine.