I see many posts about HDMI modules causing problems on the P4P, bit I have not seen any solutions.  I installed my module and was prompted to upgrade RC controller firmware.  I allowed the upgrade and rebooted everything and although I have video on my Ipad 4 mini, it freezes and gives me warnings of bad signal.  Here's what I tried so far to no avail.  I'm using the dji go 4 app latest version

1.  Switched sliders in to show osd on hdmi out and display on both output screens
2.  Switched sliders back to default which was show osd on hdmi and only show one screen (when connnected)
3.  I tried and failed to reset RC controller back to factory using DJI assistant...just hangs forever
4.  I hooked up the AC to DJI assistant to see if there were any updates.  It only showed the latest forbidden zone update available and that failed with error
5.  Tried rebooting controller, rebooting ipad mini 4, rebooting aircraft several times in desperation.

None of this stuff worked until I re-installed the original module.  Video works fine but now I'm stuck with the HDMI module update firmware on my controller.  Can't roll it back.  it will not prompt me to roll it back.  And resetting to factory defaults on radio using dji assistant still hangs forever and does nothing.

I don't have my gear in front of me here at work.  I can't tell you which firmware version #'s I have exactly.  But I KNOW that the Go app is telling me all firmware is up to date.  I know the firmware for the RC controller updated from something .00 something to something .01 something.  The issue I'm seeing is precisely desribed in other threads I'm reading.

If I missed a "fix thread" somewhere, could someone please link?  If not, can someone tell me how to roll back my RC firmware?

I had a similar problem with my HDMI module on a P3P. Eventually took it out, like you, and the original none HDMI module and controller worked fine. I bought another controller and tried the HDMI module on it and it worked first time. It may be, that for whatever reason, your controller will not match up with the module.

Well that hardly seems proper as the module specs clearly state that this module is compatible with P4 series.  I shouldn't have to buy another controller to make this work?

How do I roll back RC firmware...HELLOOO DJI ....come in please.

jdjeff Posted at 2017-9-28 08:01
How do I roll back RC firmware...HELLOOO DJI ....come in please.

If you want to roll back to previous firmware you need to sent email to DJI Support, Then they will ask for your DJI email account then......Then you have to follow what they ask you to do after this.

Thanks Nelson....

Fail.  No help there.  Is it worth trying to get this HDMI module to work or am I better off sending the module back for refund?

I stumbled upon a thread where someone said to change video transmission from "auto" to "custom" and pick a frequency.  That seems to have worked, at least at close range in the house.  I need to field test this to see if there's any glitching at flying distance.

jdjeff Posted at 2017-9-28 06:02
Well that hardly seems proper as the module specs clearly state that this module is compatible with P4 series.  I shouldn't have to buy another controller to make this work?

I agree it is not proper but after DJI and their appointed reps over here said all was fine with my system it was the only way forward. Three HDMI modules would not work. Yet at least one of them works fine in another controller. No one can tell me why.
I hope yo;u can resurrect your system.

In your 5 steps you listed I did not see that you went in to the Goggles settings and set the HDMI settings.  I had a similar issue in the beginning when I hooked everything up for the first time, once I made those changes it worked fine.  I have never used the goggles, yet, with the USB connection, so I have no idea how that might work.  Something to consider...

Genghis9 Posted at 2017-9-29 04:51
In your 5 steps you listed I did not see that you went in to the Goggles settings and set the HDMI settings.  I had a similar issue in the beginning when I hooked everything up for the first time, once I made those changes it worked fine.  I have never used the goggles, yet, with the USB connection, so I have no idea how that might work.  Something to consider...

I didnt have an hdmi cable for my goggles at the time.  This was all going on on the ipad mini 4.  I got my hdmi cable yesterday, put the video transmission to custom and the freezing up stopped as I said in my later post.  Hooked up my fatsharks and I have video to the goggles.I need to test this at a distance while flying.  I didn't like the way the signal quality bars were hovering around -100db and I'm not sure how much of the story those bars actually tell.  

Please try the following:
Go into the DJI GO App camera settings and hit Reset All Camera Settings.

jdjeff Posted at 2017-9-29 07:14
I didnt have an hdmi cable for my goggles at the time.  This was all going on on the ipad mini 4.  I got my hdmi cable yesterday, put the video transmission to custom and the freezing up stopped as I said in my later post.  Hooked up my fatsharks and I have video to the goggles.I need to test this at a distance while flying.  I didn't like the way the signal quality bars were hovering around -100db and I'm not sure how much of the story those bars actually tell.

My mistake, I didn't realize the later info...
Good Luck with getting this worked out

Kingii Posted at 2017-9-29 08:33
Please try the following:
Go into the DJI GO App camera settings and hit Reset All Camera Settings.

I will try this...thanks.  I didn't have a chance to fly still.  But I took a closer look at what I thought were signal quality bars in the video transmission page.  These bars are "evidently" indicating noise level.  So the closer to -100dbm the better...at least logic tells me.  For shiats and grins I swapped back to the stock USB module and the readings were also hovering around -100.  So I think this may be a good thing.  Still have to test fly though.

But it sounds like its worth a shot to do the above instruction...thanks.

Genghis....no problem thanks.

Resetting the camera settings actually made it worse.  Still have to select "custom" in video transmission page.  I'm going to fly it later on today.

jdjeff Posted at 2017-9-30 09:18
Resetting the camera settings actually made it worse.  Still have to select "custom" in video transmission page.  I'm going to fly it later on today.

That is strange.
For me this worked. Although I have to repeat the resetting every now and then. :-(

I did some experimenting out in the field. Using custom frequency selection in the video transmission page and HDMI module installed first.

1.  Observed noise levels in the video transmission page and manually selected the best signal...closest to -100 and green in color
2.  Connected HDMI cable and watched all noise levels increase into the red color.  The frequency I picked had clear video
3.  Flew out to about 300ft and selected auto in video transmission page and video was unusable.  Put it back to custom
3.  Flew out at a distance of 2000 ft with goggles on and lost video signal at that distance.  3.5  EDIT:  Forgot to mention at the point of lost video, I unplugged the HDMI to check if signal would increase.  It did, but it it was only 2 bars on the signal strength icon and video was fading in and out.
4.  Installed original USB module and put video in auto (as I know this is default and works
5.  Flew way past the 2000ft (3500ft and turned back) mark with clear video on the ipad.

Seems that the cable and or the goggles (fartshack) connected induces noise that substantially reduces video range...at least on my set up.  DJI wants me to send the whole kit back.  I could easily just send the HDMI module back for refund/replacement.  But I'm not the only one with this video range issue.  So replacement seems futile.  The HDMI works ok close in...I'm wondering if this is intentional.  But even the module by itself with no HDMI cable connected, for some reason reduces range compared to the original.  It's not as bad with than with the cable connected.  But the video range is noticeably less until I put the original USB module back in.  Resetting camera, selecting custom range, swapping modules for greater distance, getting a different RC? and whatever other work around there are just not practical and a sign of a flawed design.

Are people with the DJI goggles complaining of reduced range I wonder.

I called DJI and was told this time to reset RC and AC to factory defaults.  I reset the AC to factory defaults and the problem seems to have gone away...at least at close range.  Still need to check it out in the field.  There's still induced noise with cable and goggles though.