I have an older Phantom 4 Pro that uses a GL300E Android controller. I have acquired a newer Phantom 4 that I changed the flex ribbon camera cable on but can't link the unit to my RC. DJI wants me to buy a GL300C RC then use my iphone with the DJI Go Pro app. I've tried the standard link button attempt and the C1, C2, record buttons at the same time but no love. Anyway to link a cable thru the HDMI slot...or something?