FRSKY Sport passthrough telemetry doesn't work, but MAVLink does work

I’m running AP 4.1.7 on a Matek F405-SE and trying to get FrSky Sport passthrough telemetry (serial option 10) out of UART 1. I’m watching TX1 with a scope and get nothing. When I change to Mavlink (serial option 1 or 2) I see the UART outputing data on TX1.
I don’t have anything connected to Tx1, I’m just watching it with the scope.

Serial1_Options = 4
Serial1_Baud = 57
Serial1_Protocol = 10

Does anyone else have this problem?
What can I do?



s.port is an inverted protocol, so you’ll need an external inverter or else you’ll need a receiver that has a non-inverted s.port pad.

Also, serial options 4 is half-duplex. That’s not applicable to passthrough telemetry which is unidirectional.

Hi Chris,
Thanks for taking the time to reply. After a lot of experimenting I’ve gotten it to work.
When I flashed the R-XSR receiver with the latest ACCESS FW, it seems its S.Port pin changed to using F.Port. The Ardupilot serial protocol for S.Port is 10, but for F.Port I needed to use Serial1_Protocol = 23.

Both S.Port and F.Port are half-duplex (so I’ve read online) so I do need to configure Serial1_Options = 4. The advantage of this is that I don’t need to use a separate SBUS signal to carry the RC, as F.Port does both RC and telemetry over the one wire.

This now correctly sends telemetry back to my Taranix X9D+ which is evident in the Yaapu script correctly showing all the values, however in OpenTx when I search for new sensors it only finds GPS, and none of the others. I suspect this is a problem with OpenTx.



If you get the Yappu script running, then go discover new sensors, you should be able to detect some additional ones I think.

Yes, you are correct, but I don’t understand why. I would expect that the sensors shoudl be able to be detected without the Yaapu script.

The sensors are being reported as a kind of telemetry that OpenTX doesn’t understand. The Yaapu script knows how to interpret the telemetry.

Hi Oliver!
I am having problems to get telemetry out of my Xsr receiver on a Speedybee F405 v3 stack, then I saw your post!
I changed settings the same way you did, but can’t get anything out of it.
Do you have any hints?
Thanks a lot!