Gives a fairly good step by step on how to update the firmware.
Please note I followed this and ran into a issue updating the controller, but found a solution.
Background:
Where it failed for me:
Trying to update the controller via the usb/ssd card reader method. Result: Red light and no tones after 60 sec to indicate any sort of update. (Did get some intermittent beeping a good 3+ minutes later, but obviously not related to updating as light still red.) Was scared to turn it off, but did so anyway as it wasn’t going anywhere. Controller and phantom still paired up and could fire the engines, just no video at all via the app.
Checked the ssd to see if a update log had been generated for the controller and nothing.
I stupidly deleted and reinstalled the app after this to try and fix it, but then had a even worse issue of being unable to enter camera mode at all.
Solution: Check the back of the RC and see if you have the following model: GL300B (Remote controllers whose model type is GL300B can only be updated on your app.)
Now if like me you also deleted the app and re-downloaded it in the hope this would sort the issue, you will now need to do the following to get back into the part of the app that lets you do a update:
1. Make sure the RC is off.
2. Make sure your phone / tablet is hooked up to the controller via the supplied cable + you are in the DJI go app.
3. Press and hold these four buttons on the remote controller at the same time, C1, C2, Recording and the Scroll that adjusts ISO. (see link for picture if your not sure)
https://www.google.co.uk/search?biw=1252&bih=827&q=phantom+3+rc+reset+picture&tbm=isch&tbs=simg:CAQSJglR9yI3w6PjWBoSCxCwjKcIGgAMCxCOrv4IGgAMIf9OUTQoQ-ED&sa=X&ved=0ahUKEwizw4mx7avJAhUCeg8KHdTUB34Qwg4IHSgA
4. Turn the controller on (Don’t release the buttons till you see a prompt within the app allowing you to link the controller / app)
5. You should then be able to connect to camera and hit update within the settings.
6. If it’s worked you should now have the proper intermittent update beep as shown in the youtube video.
This took me about 2 hour of digging around online to find a fix and I was seriously getting peed off at how backwards it is.
The official video on the DJI site is just as bad at neglecting to mention these issues.
Hope this helps anyone else that has the same trouble.