Hello to all, i have quadcopter that sitting in shell for years now. I wanted to use it again. I have Taranis X9 Plus 2019 access model with R9M module installed Flex firmware. It has r9 mini receiver on it and i changed receiver to r9mm so i can have inverted Sport for telemetey and maybe Rc controll over Telemetry port. As i understand i need to use inverted Sport on receiver connected to Tx pin on my pixhawk telem port because pixhawk 2.4.8 doesnt have inverter and im not using external inverter. I changed serial 2 options for telem 2 port as described on ardupilot site setting Serial protocol to 10 frsky pass. Serial options i tried 4,7,160 and other that i found on wikii and none worked, i got no new sensor to discover on Taranis OpenTx latest version. Is there a way to use Fport on receiver maybe or im doing something wrong? Is there also a chance i can have Rc control over it also?
You need a diode between Tx and Rx to do the duplexing. 1N4001 or equivalent works.
Serial_options doesn’t work on STM32F4 the Pixhawk has, only on the newer F7 and H7 boards.
Thanks for your reply. Is it matter how i put diode for example anode to tx and catode to rx? Which serial options i need to set when i insert diode then?
serial_options doesn’t work on your FC, so let it at default.
I’ve never had a FrSky receiver with inverted_SPort exposed, and while I know most can be hacked, for ease of fault detection and maintenance, I’ve only dealt with regular SPort.
On regular SPort, TX goes to anode, RX and SPort goes to cathode. On inverted_Sport, probably RX goes to anode and TX and SPort go to cathode. 
There’s only 4 combinations, and you won’t break anything, lol. 