I just did this upgrade, and what a huge mistake!!! I have a Phantom 1.x...GCU/PMU, version 1.6, Naza-m Version 4.02, and have the Zenmous gimbal with go pro 3.
Before I did this firmware upgrade(which requires me to take out about 24 screws to access the mini's usb port), I had distance reading, and an arrow with degree's relative to the direction from home point.
Now, after upgrading to firmware 1.40, my distance reads nothing!!! No 0, nothing!! Same with Az..I have that symbol on my screen, but it has no reading either. This, after pulling my phantom apart a 2nd time, re-checking all wires/plugs, and re-flashing the firmware, to make sure it was 1.40, and that I didn't miss anything in the software.
Also checked Naza assistant.....
I'm so frustrated right now!! I really need the Distance the heading back to home point!!! And, I have no readings for those. Does anyone have firmware 1.20, or know how I can revert back to that firmware??
I've e-mailed DJI, but probably won't hear from anyone for months......
My advise to those thinking of upgrading ANY firmware on anything on your Phantom is-don't do it!!
Big mistake upgrading the Zenmous firmware too(1.60). Now, it's way too sensitive on tilting, and jerks to a stop. And, there is no way to make this setting "smoother"(believe me-I've been on the phone with the techs-and this is just the way it is now)...stay away from that upgrade too!!!
I really need to get this thing fixed!!! Without having to spend another $70 to get an iOSD that works!!!
I still have height information, pitch/roll, artificial horizon, battery indicator(don't know if it blinks when flow yet), but D shows nothing and Az shows nothing....and, if you turn 180 degree's from your home point and fly away-there is no diamond anywhere. You have to sit and spin to find your home point now.....good luck with that.
Best advise is to wait at least 1 month after firmware is release-and read the forums for any problems. And, if it ain't broke-don't fix it!!! I didn't need a flashing battery warning or Azimuth-but decided to "give it a try". What a huge mistake-I hope someone can help me.