Pixhawk 6C not detecting RC input (PPM/iBUS) from FS-iA6B — QGC says “Turn on transmitter”

Pixhawk
1

Hi everyone,

I’m having trouble getting my flight controller to detect any RC input. Specifically, my Pixhawk 6C flight controller is not recognizing signals from my FlySky FS-iA6B receiver, even though the transmitter is bound and the receiver appears to be working. In QGroundControl, no channels are detected and calibration fails with:

“Turn your transmitter ON”

:wrench: Hardware Setup

  • Flight Controller: Pixhawk 6C flight controller

  • Receiver: FlySky FS-iA6B receiver

  • Transmitter: FlySky FS-i6 transmitter

  • Firmware: PX4 v1.16 (QGroundControl)

:electric_plug: Wiring (PPM attempt)

I connected the receiver using the PPM/CH1 port:

  • CH1 (Signal) → RC IN Pin 2 (PPM/SBUS signal)

  • VCC → RC IN Pin 1 (5V)

  • GND → RC IN Pin 5 (GND)

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:warning: Problem Description

  • Transmitter is bound successfully (receiver shows solid red LED)

  • In transmitter settings:

    • Output mode set to PPM

  • However, in QGroundControl:

    • No channel movement is detected

    • Radio calibration fails with:

“Turn your transmitter ON”

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:test_tube: Additional Observations

  • If I disable PPM mode and connect a motor/ESC to CH2:

    • The motor spins correctly → receiver is working in PWM mode

:counterclockwise_arrows_button: iBUS Attempt

I also tried using the iBUS port on the receiver:

  • iBUS signal → Pixhawk RC IN signal pin

Result:

  • Still no input detected in QGroundControl

  • No channel activity

:red_question_mark: Questions

  • Has anyone successfully used FS-iA6B with Pixhawk 6C via PPM?

  • Does Pixhawk 6C require SBUS instead of PPM/iBUS for RC input?

  • Is the RC IN port dependent on PX4IO, and could that be an issue?

  • Is there a known limitation of iBUS support in PX4 v1.16?

  • Would you recommend:

    • Switching to SBUS receiver?

    • Using UART + MAVLink instead of traditional RC?

:folded_hands: What I’m Looking For

  • Confirmation if this setup should work in theory

  • Known issues with FS-iA6B PPM or iBUS

  • Best practice for RC input on Pixhawk 6C (PX4)

Thanks in advance — I really appreciate any insights or suggestions!

2

Hi there!
You mention

RC IN Pin 2 (PPM/SBUS signal)

What protocol are you using?

PPM should be fine Normally.
Pixhawk 6C does not use PX4IO.

Besides those, someone else will have to help you.

1 Like
3

Thanks for the reply.

I am using PPM protocol. I have tested the reciever Fs-ia6b using an oscilloscope today, confirming that it indeed is spitting out valid PPM signals.
However the pixhawk does not seem to see any signal. I.e. QGC does not show any radio input.

I am unsure on what to do. Tomorrow i will try to simulate a static SBUS signal using an arduino to see if the FC recognizes that protocol (I do not have a receiver with sbus output).

If you have any suggestions, they will be MUCH appreciated.

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4

Sorry if i understood incorrectly.

I have transmitter and reciever set to output PPM.
However I have NOT changed any parameter in QGC for pixhawk 6c.

Do i need to set protocol in QGC aswell? Or is it plug and play?