When I try to upgrade from 3.5.4 I can see these commands and then nothing happens:
Attempting upload from file /home/pi/companion/fw/ardusub.apj
Stopping mavproxy
Flashing Pixhawk…
Loaded firmware for 9,0, size: 994240 bytes, waiting for the bootloader…
attempting reboot on /dev/autopilot…
The same thing happens when I try to restore the factory default firmware.
Any advice would be appreciated.