I have a brand new Pixhawk2. Initially, when connected all seemed fine. Then, all of a sudden, it just didn't connect via USB any longer to either Mission Planner or QGroundcontrol.
- Different USB cables.
- Different computers
- Different SD cards
- Re-formated SD cards
- Tried different (old) Pixhawk which was connecting fine
- Installed octa-8 firmware instead of quad-4 firmware and back again.
None of this solved my problem.
Then, after installing a complete different fw, Rover, the Pixhawk was able to connect. Back to Quad-4 fw again and still working.
Summary: Don't forget to install a complete different fw when you're not able to connect to your Pixhawk.
Hopefully this will help any of you that might have the same issue.