I'v received my Pixhawk 4 today.
I'll go step by step what I have found happening:
First I plugged in the Pixhawk 4 to my usb port, just to do a quick check, etc. It booted up fine. But I've noticed that it intermittently starting to reset after a few seconds.
I plugged in the GPS module so that I can hear the buzzer and see status LED. Boot up fine and the power up tune played. Status LED went soft pulsing blue. Again I noticed the PixHawk reset intermittendly (At this stage I was thinking faulty USB cable).
Then I tried to connect to QGC and had no joy. Tried Mission control and also no joy.
While I'm still checking my port settings, I noticed something else, When it reset itself like that, the main indicator LED on the GPS goes off, the ACT, B/E and PWR led lid constantly on the FMU (actually with a slight flicker). the PWR, B/E lid constantly and the ACT led flicker (like normal) on I/O. Resetting the I/O works but not the FMU.
Then, the above state of LEDs started to stay like that permanently.
Obviously, I tried doing a firmware upgrade, but that does not work because of the no connect.
I tested a Pixhawk 2.4.8 with the same cable and settings, QGC and Mission control and it works perfectly.
Is there a hard reboot method I can do to clear the Flash and bootloader and try over?
Or is it just hardware?
Sorry for the long post. Have to make sure I covered everything before ordering a replacement.