https://drive.google.com/open?id=1ZeU1GfxA52WsgVGAtoAmhKbeBJkjV_D0
Seems like 6.6.9 is very stable. There was no conversation for a couple of weeks.
With this version, you can choose the mode.
1. CE mode
Set the drone's channel to 11 or 161, and reboot your drone.
2. FCC mode
Choose any other...