If you have a new Iris Quadcopter from 3DR with a FlySky RC Transmitter, you may want to add CH8 option to trigger other features. Below is a walk-through on how to add this to the standard Iris setup.
NOTE: This walk-through works by copying the settings that make CH7 work to CH8. This means you need a preconfigured FlySky from 3DR which is setup for Iris. I will do a later walk-through on how to do it generally for Er9X (OpenTx)