"Yep, always confusing the crossed TX/RX. You're right, so from the flight controller's perspective it should only have one device connected to its RX. That is one device sending it heartbeats etc."

"I've done this with my 3DR transmitter. I just soldered a Y-cable that only splits off GND and RX, TX should only be connected to one device. So to run both I have the connector with TX going to the radio and if I want to run without the radio at…"