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APM RSSI 3.3V input

Posted by Lukasz on November 15, 2013 at 4:12pm

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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:

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Here few pictures:

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

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Hope this helps anyone.


Lukasz

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Comments

  • Chris Mavrakis January 22, 2015 at 11:00am
    To anyone still reading this, I semi-solved my jumpy reading problems by removing the resistor from my filter. Turns out openLRS receivers already have a resistor, so they only need a filter. Still, I get about 10 points jumpyness :(
  • Chris Mavrakis January 22, 2015 at 10:59am
    John80, you were probably running AC 3.1, which does not have the feature. Try with 3.2!
  • John80 October 5, 2014 at 10:18am

    Where can I fond this RSSI_Range parameter? I am running the latest Mission Planner with the latest quad firmware. 

  • Chris Mavrakis July 19, 2014 at 6:35am
    I'd say anything more than 10v is fine. Keep it low though, don't go to 35v+...
  • Pyr8 July 17, 2014 at 3:30pm

    What voltage 10uf capacitor is best....16v?

  • Anton May 21, 2014 at 9:21pm

    This is the rx working in this way, the MP just processes the input data. I had a similar problem - my rx gives the ~1V as min and 2V as max and when it off the value jumps so I made the voltage level convertor and realise program filter which analyzes the data for 1 second and calculating the mean value, so I get the refresh rate of 1sec and some protection from short spikes of the voltage.

  • Chris Mavrakis May 21, 2014 at 3:18pm
    So, I made the cable, with cap and resistor. I do get values on the OSD but they're a bit strange. Especially when my Tx is OFF, the reading jumps around a lot.

    I've used the "view raw" setting but still, when tx is off it jumps about 30%...
  • Chris Mavrakis May 21, 2014 at 12:04pm
    Thanks Anton, but I don't get what you say. My RSSI out is 0-3.3V. Can I just connect this to APM?
  • Anton May 21, 2014 at 10:19am

    Still wait for possibility to set the min and max voltage value as rssi min and max to configure rssi out with MP for proper data displaying.

    Chris Mavrakis
    Currently there is to ways: 0-3.3V and 0-5V corresponds to 0-100%. If your rssi voltage from 0 to >3.3V than the divider will help.

  • Chris Mavrakis May 21, 2014 at 1:09am
    So copter guys have to wait for 3.2.

    I'm wondering, is there a way to make it work on 3.1? Maybe a voltage divider to drop the 3.3V down to what the APM "by default" thinks is 100% signal?

    What's APM's idea of 100% signal, in voltage?
This reply was deleted.