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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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103, pwm, pixhawk, rssi, pin

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Replies

- - - - Mark Jones > Steve Cain May 24, 2014 at 1:09pm
        
        Thank you for the quick response ! I will try changing to channel 8 , and hopefully get some results ...thx again.
        
        Rob > Mark Jones May 24, 2014 at 12:54pm
        
        Just had the same issue - APM 2.5.2 and MinimOSD - looks like on CH7 the RSSI is not working in MimimOSD, on CH8 it works though. EZUHF, PPM Muxed, RSSI on CH8. Only problem now is that its reversed ...
      - mP1 > Steve Cain March 13, 2014 at 7:05pm
        
        Good stuff, minimosd-extra is always evolving, its always worth grabbing the latest of all the artefacts and trying them because new stuff is always appearing.
    - Steve Cain > mP1 March 13, 2014 at 6:10am
      
      MP1
      
      Thanks for the tip, (I set ch8 to output RSSI, which it is doing), but I don't see how to tell the MinimOSD to read ch8 as the RSSI channel in the config tool.
      
      I am running 2.3.0.8 minimextra config tool and version 2.3 copter in my quad.
      
      Which screen do you find the RSSI channel selection in the config tool? I don't see it.
      
      What setting if any do i need to make in MP?
      
      Thanks for your help.
Steve Cain March 11, 2014 at 6:37pm
Some context for my post above from the Pixhawk overview.

Virtual Pin 102: Servo power rail voltage. This is an internal measurement of the servo rail voltage made by the IO board within the Pixhawk. It has 3:1 scaling, allowing it to measure up to 9.9V.

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). Can alternatively serve as SBus out but not yet implemented.

per the pixhawk overview
- Extensive I/O interfaces with dedicated connectors
  
  Fourteen PWM servo or ESC speed control outputs.
  
  Five UART (serial ports), one high-power capable, 2x with HW flow control.
  
  Two CAN I/O ports (one with internal 3.3V transceiver, one on expansion connector)
  
  Spektrum DSM / DSM2 / DSM-X® Satellite reciever compatible input: Permits use of Spektrum RC Transmitters.
  
  Futaba S.BUS® compatible input and output.
  
  PPM sum signal input.
  
  RSSI (PWM or voltage) input.
  
  I2C and SPI serial ports.
  
  Two 3.3 volt and one 6.6 volt Analog inputs.
  
  Internal microUSB port and external microUSB port extension.
  
  Contains its own on board microcontroller and stacks with the FMU.
Steve