EDIT: Figured out what was going on, and it did turn out to be simple.  As tempted as I am to delete this out of embarrassment, I'll leave this post present and put the details at the base of the post for those interested or if someone else with the same problem stumbles onto this.

Hi all, sorry to bring some old tech up, but I am a bit lost when it comes to getting my A2 Flight Controller compass to calibrate.

I bought an unused S900 kit + A2 as an open box a couple of years back, and have been assembling it over the last 12 months.  I am very much a beginner and have been gleaning information and learning as I go.  It's been a challenge, but I'm ready to put it into the air.

I am using an external FrSky X8R receiver and a Taranis+ transmitter.  Battery is 16000 mAh 6s.  I have inputted as much basic information as I can into the A2 assistant software to suit, although I have not made any adjustments yet to Gain values or motor idle speeds.  The assistant software is version 1.9.

The issue is that I can't get it into calibration mode.  All of the components are fully up-to-date with their latest firmware, but when I set the drone up outside, I either get a set of continous red flashes on the LED module, and then after a while of unplugging/plugging the battery again I get a constant and rapid green and yellow flash.  I mapped a 3-position switch to the U-channel, and I can see the channel map values changing when it's plugged into the A2 assistant software and I'm flipping the switch back and forth, but the LED light  on the drone will never turn blue, even when I'm out in the middle of an open field away from any magnetic interference and rigourously flipping the U-channel switch.  When it's plugged into the assistant software the only error message is about Abnormal Compass data, which does not go away.  The IMU is calibrated and ready.   I can test run each motor successfully through the software, but cannot get the motors to spool out in the field.

I have seen posts from other users talking about changing flight modes, but this is confusing and I'm not sure what this means.  When I flip the switch for the U-channel, it's supposed to change between modes and trigger the compass calibration process?? - but this isn't happening.  The strange thing is that on the assistant software, it will display MODE: Atti RC Status: Normal down on the bottom of the screen, but if I switch the U-channel is goes to MODE: GPS Atti RC Status: RC Lost.  Switching the U-channel back will not change the MODE, it will stay on GPS Atti no matter what I do, no matter how many times I flick the switch, no matter what position the switch is in.  The RC Status does however cycle between Normal and RC Lost.

Can someone please tell me whether this is normal behaviour?  Why can't I switch between flight modes?  I'm not sure what I am doing wrong, or what I'm missing.  If someone could also explain the flight modes to me and which position on the U-channel switch is supposed to be ( and whether it can be changed ), that would be helpful.  

The closest I have found to an answer is this thread.  The forum member who posted it could also not get into calibration mode.  Apparently they figured out that the travel on the switch was incorrect and adjusted it.  I don't really know what this means or what the blue boxes are that they are referring to.  The travel of my U-channel is sitting on a little over 10,000 in either direction on the channel mapping - enough to cross the red mark on either end.  

Any thoughts from experienced users ( current or historical ) would be appreciated.  I can upload screenshots or maybe video if needed.  

Hopefully it's something simple.

**Update: The other thread that I referenced was on the money, but I didn't understand what the person was referring to.  The blue boxes are on the Basic - RC tab of the software assistant next to the receiver type, where you can see the U-channel cycling as you use the switch under the heading "Control Mode Switch".  When cycling the switch, the selection pointer on the scale would exceed the top and bottom boxes and only activate the Fail Safe boxes instead.  I figured out how to lower the limits on my transmitter for that switch in both directions until the selection pointer would successfully fall into the boxes for the flight modes.  

I was then able to get into calibration mode successfully, and was nearly ready for flight.

After a few more hiccups ( like swapping around the channels for the main sticks and making sure the throttle was correctly assigned and not reversed ) I managed to fire up the drone.  I stop/started it a few times while it sat on the ground until I bit the bullet and let the throttle slowly increase to lift-off.  Unfortunately the drone tipped itself over while still on the ground and broke a few prop blades.  It seems I have to get everything a bit better balanced or else there may be an issue with something else.

To any future readers, hopefully you find out what info you need.  Good luck and happy flight.

EDIT: Figured out what was going on, and it did turn out to be simple.  As tempted as I am to delete this out of embarrassment, I'll leave this post present and put the details at the base of the post for those interested or if someone else with the same problem stumbles onto this.

Hi all, sorry to bring some old tech up, but I am a bit lost when it comes to getting my A2 Flight Controller compass to calibrate.

I bought an unused S900 kit + A2 as an open box a couple of years back, and have been assembling it over the last 12 months.  I am very much a beginner and have been gleaning information and learning as I go.  It's been a challenge, but I'm ready to put it into the air.

I am using an external FrSky X8R receiver and a Taranis+ transmitter.  Battery is 16000 mAh 6s.  I have inputted as much basic information as I can into the A2 assistant software to suit, although I have not made any adjustments yet to Gain values or motor idle speeds.  The assistant software is version 1.9.

The issue is that I can't get it into calibration mode.  All of the components are fully up-to-date with their latest firmware, but when I set the drone up outside, I either get a set of continous red flashes on the LED module, and then after a while of unplugging/plugging the battery again I get a constant and rapid green and yellow flash.  I mapped a 3-position switch to the U-channel, and I can see the channel map values changing when it's plugged into the A2 assistant software and I'm flipping the switch back and forth, but the LED light  on the drone will never turn blue, even when I'm out in the middle of an open field away from any magnetic interference and rigourously flipping the U-channel switch.  When it's plugged into the assistant software the only error message is about Abnormal Compass data, which does not go away.  The IMU is calibrated and ready.   I can test run each motor successfully through the software, but cannot get the motors to spool out in the field.

I have seen posts from other users talking about changing flight modes, but this is confusing and I'm not sure what this means.  When I flip the switch for the U-channel, it's supposed to change between modes and trigger the compass calibration process?? - but this isn't happening.  The strange thing is that on the assistant software, it will display MODE: Atti RC Status: Normal down on the bottom of the screen, but if I switch the U-channel is goes to MODE: GPS Atti RC Status: RC Lost.  Switching the U-channel back will not change the MODE, it will stay on GPS Atti no matter what I do, no matter how many times I flick the switch, no matter what position the switch is in.  The RC Status does however cycle between Normal and RC Lost.

Can someone please tell me whether this is normal behaviour?  Why can't I switch between flight modes?  I'm not sure what I am doing wrong, or what I'm missing.  If someone could also explain the flight modes to me and which position on the U-channel switch is supposed to be ( and whether it can be changed ), that would be helpful.  

The closest I have found to an answer is this thread.  The forum member who posted it could also not get into calibration mode.  Apparently they figured out that the travel on the switch was incorrect and adjusted it.  I don't really know what this means or what the blue boxes are that they are referring to.  The travel of my U-channel is sitting on a little over 10,000 in either direction on the channel mapping - enough to cross the red mark on either end.  

Any thoughts from experienced users ( current or historical ) would be appreciated.  I can upload screenshots or maybe video if needed.  

Hopefully it's something simple.

**Update: The other thread that I referenced was on the money, but I didn't understand what the person was referring to.  The blue boxes are on the Basic - RC tab of the software assistant next to the receiver type, where you can see the U-channel cycling as you use the switch under the heading "Control Mode Switch".  When cycling the switch, the selection pointer on the scale would exceed the top and bottom boxes and only activate the Fail Safe boxes instead.  I figured out how to lower the limits on my transmitter for that switch in both directions until the selection pointer would successfully fall into the boxes for the flight modes.  

I was then able to get into calibration mode successfully, and was nearly ready for flight.

After a few more hiccups ( like swapping around the channels for the main sticks and making sure the throttle was correctly assigned and not reversed ) I managed to fire up the drone.  I stop/started it a few times while it sat on the ground until I bit the bullet and let the throttle slowly increase to lift-off.  Unfortunately the drone tipped itself over while still on the ground and broke a few prop blades.  It seems I have to get everything a bit better balanced or else there may be an issue with something else.

To any future readers, hopefully you find out what info you need.  Good luck and happy flight.