Hello

I have an MAMBA F405 DJI MINI fligt controller and will use it with my Futaba T14SG and SBUS receiver instead DJI RC.
On the FC I connected my SBUS receiver on RC (TX1) port like the FRSKY R-XSR on the electrical plan. In Betaflight port UART1 is set to serial-RX and receiver configuration is on serial-based (sbus) and sbus.
But my problem is that I don't receive any signal inputs in betaflight while moving the sticks. I tried also to play with the following settings:
serialrx_inverted 
serialrx_halfduplex
sbus_baud_fast

Still no input signal. I know Futaba SBUS is inverted (3.3/5V signal 0, GND signal 1), can't find any information if this is possible on the port I connected the SBUS. Is FRSKY also inverted like the Futaba SBUS or inverted to the SBUS from Futaba so basically
not inverted?
Anyone know what I could try? Or do I need an inverter for the SBUS signal?

Futaba (the inventor of the SBUS protocol) uses a real inverted SBUS signal with 5V representing a binary 0 data bit and 0V represents a binary 1 data bit.

By comparison, FrSky uses an inverted version of the Futaba SBUS signal (so an inverted inverted SBUS signal if you like) whereby 0V represents a binary 0 data bit and 5V represents a binary 1 data bit.

The RC input on the Mamba F405 flight controllers has a hardware inverter on it designed to take the FrSky version of an SBUS signal which it then inverts to make it like a native Futaba SBUS signal. The problem with feeding a native Futaba SBUS signal into the SBUS pad is that the hardware inverter will (incorrectly) invert the signal to make it like a native FrSky SBUS signal which means the FC can't understand.

Fortunately the Mamba F405 FC uses a software switchable hardware inverter on the RC pad input which you can simply just switch off. To do that, run the following commands in the CLI and see if you then get stick movements in the Receiver tab. I'm not 100% sure if you need serialrx_inverted switched on or off, but start with it off which is the default setting.

Thanks for your information and the help. Even disable the inverter in the code didn't work. So I flashed the newest firmware and cleard the settings, without any code the stick movement did work.

Now I have the next problem, it works as long as the DJI air unit is unglugged. When the air unit is plugged in, the RC input doesn't work anymore. Do you have also a software solution for this? Otherwise I will try to cut the SBUS cable from the air unit to the FC.

That's good news

The SBUS pin in the DJI socket and the RC pad are both connected together internally on the board via copper traces, so the SBUS signal from the Air Unit will be interfering with the Futaba signal on the RC pad. The only way to stop that is to remove the (yellow) HDL wire from the plug, and while you are at it you can also remove the (brown) GND wire as well because that's not needed either.