Below is a quote of a post I made in RCGroups. There was some question about the Magnetometer. I put in some of my observations about Calibrating a Revolution board and its failure to arm sometimes. I do not know if any of these suggestions could be added to the firmware. These comments are not meant to be critical, I hope it is more like feedback to the project. Getting a revo up and flying without Mag or GPS is not too bad. But trying to add mag or GPS ends up with a aircraft that will not arm, more often than not. This can be very frustrating, especially when a CC3D can be setup very quickly and be ready to fly. I wonder if something can be done to make the advanced features easier for us noobs!
Thank you for your efforts on LB GCS it works really well.
http://www.rcgroups.com/forums/showthread.php?t=1809971&page=84#post34511860The GPS/Mag they are working on is a DJI compatible unit. It combines both on a 4 wire set. You will only need one port to connect both rather than one port for GPS and another for mag. The one they recommended in the forums was about $30.
As to calibration of the revolution. Yes it is a real PITA. It needs to be improved. You can recalibrate several times and still end up with a model that spins in circles in Flight Data. Set your multi-rotor on a concrete slab and you cannot arm it as the mag goes red in system health. So then you have to dig out a laptop or a tablet to turn off the mag. Same with the GPS. So if you want to fly indoors you have to have a setup session just to clear the red boxes by shutting them off, then you have to recalibrate. All the calibrations appear to be interdependent.
There needs to be a way for the board to fall through the mag and GPS so you can fly in a shop. Give you a warning set of lights but then allow you to fly.
Example I checked the mag and GPS on the bench. The mag was orange but allowed me to arm. Set on the concrete floor(rebar) and it would not arm. Tried several times then dug out the tablet to see what was going on. Orange on the bench but red on the floor.
So no flying indoors unless you turn off features and recalibrate. My Yuneec will fly in the shop, not happy about it (LED's flashing red and white), but it will fly. So there must be a way to fall through the offending sensors and still allow 6dof flight.