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Pixhawk PWM input for RSSI (EZUHF)

Posted by Steve Cain on March 11, 2014 at 6:20pm

Gents I need your help.

I recently upgraded one of my 2.6APM powered quads to a Pixhawk.  One of the reasons I went ahead and did this is because the Pixhawk is supposed to take PWM RSSI signals directly (into the Sbus port aka Pin 103) and I could ditch my PWM to analog conversion circuit is used in my APM.

I have verified that my EZUHF receiver is outputting RSSI in PWM form on one of the channels. (it will move a servo appropriately when the RF gets weak or disappears... and it worked fine for the APM as an RSSI input via a PWM to analog conversion circuit)

And, I have hooked up the PWM RSSI output to the Sbus port (pin 103).... it does nothing.  Shows zero RSSI on the OSD no matter what.

I can't find any useful description of how to configure this in the wiki, mission planner or this site.

How do you make a Pixhawk show RSSI from a PWM input on pin 103 as its advertised?

Thanks for your help.

Steve

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Tags: 103, pwm, pixhawk, rssi, pin
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Replies

    • David m > David m October 22, 2014 at 6:34am

      Here is a tutorial video I made for the EZUHF RSSI / Link Quality with APM 2.6 or Pixhawk

      https://www.youtube.com/watch?v=rh7-D96FIK0 

      • Sergio Vial > David m December 12, 2014 at 9:29pm
        Dear David, I follow up every step on your video, I have the same or even newer firmware in the Minimosd, but the RSSI appear lower when the transmiter is on, and higher when the transmiter is off, so the Link strengh is near 0% when is full strengh and near 100% when the transmiter is off, what I did wrong?, thank you for your very valuable assistance.
        • David m > Sergio Vial December 13, 2014 at 8:11am

          You have done nothing wrong.

          Unfortunately the RSSI is inverted with the EZUHF. 

          In the movie you will see that I chose to use Link Quality which is non-inverted and responds to degradation from interfering signals. In my opinion Link Quality is the better choice anyway.

          • Sergio Vial > David m December 18, 2014 at 6:47pm
            I am not sure, but eventually I chose the link quality on chanel 8, so I cannot understand why it shows reversed on the Minim osd, but I will repeat the procedure to be sure before complaint.

            Regards
  • tenright August 12, 2014 at 4:11am

    I've tried all of the above but can't seem to get it working.

    I am using the 2.4r727 config tool and have flashed to firmware 2.4r726.

    • Steve Cain > tenright August 31, 2014 at 1:29pm

      If you haven't done it already, go to the minimosd extra thread, and download the firmware from the front page of that thread ...2.4r780 or 2.4r781.

  • F. C. Bearsch June 20, 2014 at 1:40pm
    Does this work?
    Going to try
  • Nathan Kinney May 10, 2014 at 1:04pm

    Does anyone know if or when the RSSI over PWM feature will be delivered?

  • David Gu March 12, 2014 at 10:19am

    Hi Did you ever solve this?

    I have a PIXHAWK and a Futaba T8FG and would like to buy a EZUHF for the futaba and then a 4CH RX or the 8CH diversity and use the PPM. Only it will suck to pay 260+ bucks and not have it work. 

    • Steve Cain > David Gu March 12, 2014 at 5:14pm

      David,

      The PPM output from the EZUHF works nicely with both APM 2.6 and Pixhawk.  I highly recommend the EZUHF radio gear.  I have 4ch, 8ch lite, and two 8ch diversity receivers.  All are used for 8 channels (including the 4 channel one) via PPM sum output on channel 1.

      The current "issue" I am having is simply that the PWM (pulse width modulation) output for RSSI or Link Quality that can be sent from the EZUHF receiver  has to go through a special home made circuit to turn the PWM signal into a readable analog signal so the APM or Pixhawk can get signal strength or link quality to show up on my OSD.  I have used 1cell non-brushless speed controllers from hobby king for this for the last year with the APMs and I'm sure it will work ok with the Pixhawk too, I'd simply prefer a direct connection. (as they promised)

      I did hear  from Craig at 3DR that the PWM input for RSSI will be included in a future software release...he did not indicate which one... I have not yet looked to see if it is on the list for 3.2 which is at least 6 weeks away according to Randy.

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