title_body: How to fix OSD flickering? I just changed my Diatone R349 flight controller because the old one broke. On my first test flight, I noticed the OSD is flickering very bad, sometimes losing it for more than 1 second, even when not armed.
  
  The video feed is good, just the OSD flickering.
  
  The VTX and camera are powered by an external 5v regulator. The rest is powered by the FC.
  
  I've read that it could be a ground issue.
  
  Could it be something else?
  
  EDIT:
  This is my current hardware and wiring diagram.
upvoted_answer: I fixed it by adding a common ground between the 5v regulator and the flight controller. I can't explain the science behind this, but I took the answer from this video from Painless360
  
  The flickering is completely gone, even when I punch the throttle.
  
  New wiring diagram:
  
  
  EDIT: I will leave the post unanswered until someone intelligible explains this, and maybe other OSD flickering causes just to keep the post general to the question and not specific to my hardware and wiring.