What's the current status of RSSI support on Pixhawk?

I'm been searching and reading (even in Github), but haven't found any definitive answer(s) yet.

Is this something that is already supported or is it in a todo queue somewhere (which I can't find)?

The manual refers to PWM RSSI. Unfortunately, there are 2 flavours of PWM (servo PWM as EzUHF uses for RSSI I believe, and 'normal' PWM as FrSky outputs for RSSI). The manual isn't clear on which it's referring to, or if it's both:


If it's referring to servo-PWM {

  then I must make a RC filter for my FrSky RSSI output


else {

  just connect it directly.



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  • Hi,

    I've Frsky x8r and Pixhawk with the lastest firmware on board. Can you explain me how make the connections between the Frsky x8r and the Pixhawk. I know I need a RC filter.

    Thank you very much.

  • There is no code AFAIK in APM for pwm rssi. We read analog voltage, that's it.

    Connecting directly might work but most likely there will be delay in the rssi information received by the pixhawk, or it will jump up and down all the time.

    Just use a voltmeter on your rssi signal and see what happens, APM will the same thing.

    I personally use the RC filter on my D4R, D8R, X8R, X4R..

    To be complete, having PWM rssi in APM should be possible and I believe there is a PR in Github for that .. never commited AFAIK

  • I tried with the Iris, join ch 2 of  frsky D4R-II rx to sbus on pixhawk, and it works. By the way I am using arducopter 3.1.5

    PS dont forget this: Quote

     "Reply by Matthias Badaire on May 13, 2014 at 3:08am


    Virtual Pin 103: RSSI (Received Signal Strength Input) input pin voltage (SBus connector output pin). This is the voltage measured by the RSSI input pin on the SBUS-out connector (the bottom pin of the 2nd last servo connector on the 14 connector servo rail). 

    Modify RSSI_PIN to 103


    Modify RSSI_RANGE to 5.0


    (I modified RSSI_RANGE to 3.3 and get value rxrssi of up to 99 in MP)

    • So I already did this and I'm only getting 100%, 75% or 0% in the RSSI

      • Are you using x8r rx? In my case I have a pretty good resolution..... I regularly see values in mid 90, 80, 70 and 60..... Never gone lower though... 

  • Out of my experience, x8r + pixhawk do not need a filter, just plug and play. First read it on the 3.2 beta forum, tried and it works, but have not seen it documented thought.

    • Do you want me to take a video?
      • it's ok man I just want to know if it's working ok as the guy above wrote it won't register correctly

        • Looking at RSSI on taranis vs rxrssi in MP difference is about 8-9% but I think this is more due to taranis showing its own RSSI i.e. how well it receives the telemetry from x8r (which uses more bandwidth thus introducing more errors) also taranis is on the ground with all the wifi mess and x8r in the semi-clean air, so I think this is a legitimate difference. 

    • Can anyone confirm this?

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