I've just upgraded my X8 to Copter 3.5 RC8.
The first flight was uneventful, just a bit of additional Alt-hold oscilation, however the second flight triggered an EKF failsafe, and by the looks of it all the devices connected via i2c stopped providing data.
On i2c I have connected Optical Flow, Lightware SF11/C, Compass and LED.
(previously, SF11/C was connected via serial, but I wanted to free up the serial port for a 2nd GPS)
I've checked the wiring and nothing seems to have come loose.
I'm thinking either I've overloaded the 5v supply on the i2c port (although all these devices together use <500mA)..... or maybe there's a problem with running Lightware devices on i2c.
On a separate note, I Optical Flow doesn't seem to stay enabled after power cycling some times. (I had double checked it was enabled before this flight, but the log shows it was disabled again).
2017-06-18 14-12-06.bin (1.5 MB)