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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  • Thanks Dusan, that's exactly what I did, except for resistor. I've used 4.7k. This will work fine as well.

  • Great work. Can you post a diagram of the wiring and components required? For us lowly non-electrics type.


  • Admin

    Good work. I am sure lot of silent APM flyers appreciate this. Thanks for posting.

  • Gary, thanks for wiki page, will be useful for others.

    Dean, you're welcome :)

    Adrian, RSSI_RANGE parameter was added to APM firmware, so once uploaded all ground control clients will pick it up without need of making changes in say Mission Planner. (maybe except for param description)

    The change in firmware is better because all clients like Mission Planner, APM planner for Mac, client for Android and others will receive same rx rssi value from APM.

    I have made code pull request for APM code #688 (needs to be approved):


    We could make this rescale param available just in Mission Planner and this wouldn't require having any firmware changes however all other ground control stations such as client for Android or one for Mac would show different value (not rescaled) which may be misleading.

    If my code change request won't be approved/pulled, I will try my chances with adding this param to Mission Planner only :)

  • Can this setting be added to the official mission planner?

  • This will certainly come in useful. Thanks mate!

  • This looks really useful Lukasz,

    Ive already turned it into a common wiki page here: http://planner.ardupilot.com/wiki/common-rssi-received-signal-stren...

    I will probably still edit it a bit to make it better fit out normal format, but this is one excellent page as it stands.

    If you don't want me to use it on the wiki or if there is anything you would like me to add or change, please just let me know here and I will be happy to do so.

    Great Job| 

    Best Regards,


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