The FrSky telemetry does not transmit the radio channels. What you have there looks like a D4R-II. You need to set the jumpers according to its manual to put it into PPM-SUM mode and then connect port 1 to the S.BUS input of Pixracer.
Then you can go back to FrSky telemetry. Check that you get the system voltage on your remote.
That’s an XSR receiver in the photo, and it has no configuration jumpers. The black and red wires from the XSR must be connected to GND and 5V of the Pixracer RC input cable. You can connect either the SBUS or CPPM (white or green) to the RC_INPUT line of the Pixracer, but beware that I have had problems with the XSR’s SBUS output generating garbage after a few minutes. I’m currently using the CPPM output because of that problem. The yellow wire is the S.port bus, and it should connect to both FRSKY_IN and FRSKY_OUT on the Pixracer.
Can someone please explain why the SPORT is connected to both RX and TX of FrSky? Seem very odd. What kind of data is transporting to FrSky? If I only connects the SBUS or CPPM to RCin, will that be sufficient enough to get Radio signal? SInce we can preserver the FrSky for other Serial Sensor? Thank you.
S.port telemetry is half-duplex bidirectional with both transmit and receive on the same wire, but the PX4 device driver configures the UART in normal full duplex mode with separate RX and TX pins.
