I am using a Teensy 3.5 to build a box to control everything on XPlane's GNS430/530, and I have run into a couple of snags.
First, I have searched all over the web looking for how to detect that the GNS430 MSG indicator is on.
I have found how to send the MSG button press from my Teensy board to XPlane with sim/GPS/g430n1_msg, but I can't find out how to tell it is needed.