APM RSSI 3.3V input


For some time I wanted to add ability to provide RSSI from FrSky receiver to APM.

RSSI_PIN parameter works fine for that however some of receivers such as mine FrSky D8R-XP outputs 0 - 3.3 V. For that purpose I've added new param and called it RSSI_RANGE.
This was also issue requested before: https://github.com/diydrones/ardupilot/issues/648
After voltage rescaling it works. rxrssi is shown in scale 0-100.

And added ability to rescale in params:


Here few pictures:



I've used 4.7k resistor and 10uF capacitor to filter pulse signal coming from receiver's RSSI output.



Hope this helps anyone.


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  • dumb question, but should the RC filter be closer to the receiver, to the output, or is it irrelevant?

  • I just wonder if the "rssi range" will be in arduplane  ?

    fingers crossed

    cheers darren

  • I've just checked with Randy, and he told me that the rssi 3.3v code update did not make it into AC3.1. It will be in the AC3.2 First release candidate due in two weeks' time.
  • Hi lukasz,

    Im experiencing the same as Farmertom, I've just updated my firmware to 3.0.1 for my tbs discovery but I cannot see the RSSI_Range. I did follow your instructions in order to make the signal work with the components you suggested.

    Kind regards,


  • My branch of code is here https://github.com/lukaszkn/ardupilot

    I've made pull request so it was added 25 days ago.


    APM Plane, APM Copter, APM Rover source. Contribute to lukaszkn/ardupilot development by creating an account on GitHub.
  • Righto, got the filter all hooked up and receiving RSSI but only showing around 60% when it should be 100%. Would you have the code you edited available so that we can compile ourselves. I'm just impatient, and cant wait for it to be added into the arduplane release. Thanks :)

  • The wiring diagram should be posted on the wiki page also :-)

  • Hi,

    When will this be made available? I just downloaded/install the latest firmware and the RSSI_Range parameter did not show up? Am I missing something? Too soon?



  • Thank you for adding this! ;)

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