Copter 3.6.8 PixRacer w/ FrSky R9 Slim+ RX Telemetry not initializing

I have a copter that has a PixRacer running 3.6.8 and has been running great for some time. I originally had a FrSky X4SB RX and was using the FrSky port on the pixracer to pass telemetry to the RX and everything worked great. I decided to upgrade to the new R9M and the R9Slim+ and thought originally it would be a direct drop replacement. After installing and finding out that the Telemetry was not passing I started to search the internet for help. Others claim to have great success with other FC other claim they did have a problem until the firmware on in BetaFlight or others have been fixed. What I am finding is that when the R9Slim is powered up with the PixRacer the telemtry com fails to pass anything. But if I boot the PixRacer first and the wait for it to completely load then power the RX telemtry starts to flow. I reached out to frsky and they claim it is the FC that has the problem not the RX because others are working. Is there a chance to add a delay to eliminate a timeout that must be happening when the S-Port on the R9 RX is used to pass telemetry?

Edit - Just one more thing I did purchase a " FrSky Yaapu Telemetry Converter" to see if it was just a problem with the FrSky Serial4 on the PixRacer. Using the converter I plugged it into Telem2 and set the protocol to 10 and also found the same issue. A race to recognize the S-Port happening. While on Telem2 again if I boot the PixRacer completely first then power the RX telemtry starts to flow on Serial2.

Thanks again for all you awesome work…

I don’t have any problem with a PixRacer and an R9 Slim (not +) and Frsky telemetry on Latest Rover. Serial 4 Protocol 10. I wouldn’t think Copter would be any different.

You are the 2nd to report passthru telemetry problems on the Slim+

I don’t have one, but FrSky’s pdf says it’s an already inverted port, so it needs an inverter if connected to the Racer’s special FrSky port and probably a straight cable and a diode on a regular serial, like Telem2.
I don;t think a “yaapu cable” will help.

If you have an F7-based FC, you can load 3.7-dev and play with the SERIAL_OPTIONS.

The slim+ has an inverted s- port on pin 7 I think which is also labeled rx. this is what was supposed to make this receiver so versatile with f4 controllers because on other receivers you had to hack the board to get uninverted s-port. frsky really confuses things because they are inverting the inverted I guess. The standard s port should not be different on the r9slim+ than other receivers but there is something off for sure. I did try both the standard s-port and the inverted s- port. The only one that works at any level is the standard s-port but only after the pixracer is fully booted then boot the receiver and telemetry flows.