Just use the DJI Assistant 2 PC application and connect it to the
P4P via USB (with the controller turned on an linked to the
P4P via the normal radio channel.) When performing the update the
P4P, controller, and battery (if update is available) will all be updated together.
Edit: Oops, I think I provided bad info above. My controller displayed 'Updating' during the firmware update but I now think that it was just advising me that the
P4P was currently updating and not available, not that the controller itself was updating. If you want to update the controller go to:
DJI Phantom 4 Pro – Specs, FAQ, Tutorials and Downloads and then scroll down to the firmware update area and follow the instructions. Basically you download the update and place it on an SD card that you then insert into the controller.
Another Edit: The controller update is for the
P4P+ only, not the
P4P.