Sending AUX through SBUS

Hi there, does anyone know if it is possible to send the AUX signals through SBUS on the Cube Orange? The docs indicate that the 8 MAIN channels are processed by the IO chip and can be either output through PWM or SBUS, whereas the AUX ports are processed by the FMU chip and output through the PWM ports.

I am using the Cube Orange together with the PX4 flight stack. I want to make sure whether it is a hardware or a software limitation.

Are you saying you have signal input from AUX OUT port? Then send it out via SBUSo port?

I’m not sure if I understand you correctly. I’m having outputs from all 6 AUX OUT ports to ECS/servos. I don’t want to use the PWM ports on the carrier board. The MAIN OUT outputs can be sent through the SBUS output port on the carrier board, but I want to know if it is somehow possible to send the AUX OUT outputs through the same SBUS port, too, or if it the hardware is limited to only outputing the MAIN OUT via the SBUS port.

In Ardupilot you can configure servo to sbuso, so I don’t think there are any hardware limitation.

But isn’t it a passthrough of RC signals that are supposed to actuate, for example, a gimbal with the RC joysticks? In my case, I want to output the AUX OUT signals through SBUS which are coming from a mixer, not from the RC.

Servo channels are not necessarily binded to RC.

For example, you can tell it to stay at specific position. They are not essentially controlled by RC.

I don’t really get it. Do you mean the control signal of sbus come from an external source? Then why don’t you simple control the servo without having it passing through the autopilot? Or do you need it being merged into other sbus signals from autopilot?

Sorry for the confusion, maybe I am not specific enough. I will try to explain my problem in more detail:

I am not using ArduPilot, but the PX4 flight Stack. I’m not sure how the mixer in ArduPilot is working in detail. In PX4, the mixer receives control commands like a roll rate, pitch rate, throttle rate, etc. and translates these commands into PWM output signals for MAIN OUT and AUX OUT

In my setup, the vehicle has 9 engines with ESC and 4 servos. Therefore, I need at least 13 PWM outputs to be able to control them. All engines and servos are controlled by the autopilot (flight controlker) and the mixer translates the control commands into actual PWMs. 8 of these PWMs are given out through the MAIN OUT ports and the other 5 outputs through AUX OUT.

When I am using the physical PWM ports on the carrier board, I have to use an SBUS encoder to convert them to SBUS. However, when I activate the physical SBUS port in PX4, only the 8 MAIN OUT signals are given out through the SBUS port, therefore only the 8 engines/servos specified in the MAIN mixer can be controlled using SBUS. However, the SBUS of the Cube Orange outputs 16 SBUS channels, but only the first 8 can be controlled.

I wonder, if it is a limitation of PX4 or of the Cube Orange. The reason why I ask this question is, because in the Cube Orange Docs (, the system architecture indicates that only the 8 MAIN outputs are given out through the SBUS port (since the IO chip processes them and only the IO chip can output SBUS signals). However, it seems to be possible with ArduPilot to control more than 8 SBUS signals through the SBUS port after reading your links. But in my understanding, the SBUS ports 9-14 are not controlled by the mixer but by the RC (RC pass through). Please correct me if I am getting it wrong.

I think this is a limitation from PX4, as Ardupilot is capable of doing this. You may need to confirm this from PX4 developers.

But one thing I did not understand so far with ArduPilot: are the servo out (SBUSo, Channels 9-13) signals processed by a mixer or are the signals passed by the RC to control a gimbal (for example)? Is it possible to address the SBSU channels 9-13 with a mixer for autonomous flight?

I believe they are processed by mixer rather than a simple pass through. But you may want to confirm this by asking from Ardupilot developers.