Discussions

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

You need to be a member of diydrones to add comments!

Join diydrones

103, pwm, pixhawk, rssi, pin

Email me when people reply –

Replies

- - - - Steve Cain > Mark Jones May 24, 2014 at 1:04pm
        
        Mark,
        
        There a couple of "gotcha's" in the setup.
        
        1) this works with 2.4r727... not the earlier releases
        
        2) despite the ability to select different channels the minim OSD software only works with channel 8. (I think this is where your problem is)
        
        3) I feed the PPM sum stream to the pixhawk, not individual channels. I suspect it will still work with individual channels but my setups are all via a sum stream...
        
        There is nothing you need to do in mission planner to make this work.
        
        I suggest setting the ezuhf signal quality to channel 8 and you will be good to go (other than calibrating it.)
        
        A couple other suggestions... I prefer signal quality to RSSI because it is possible to have really strong signal strength but poor signal quality... this happens when you have things like the camera putting out noise on the 433MHz band.
        
        To find zero and 100% set the minimosd to raw first and write down the numbers that appear when you switch the transmitter on and off... this will give you the figures to calibrate full and null signal... then go back into minim OSD put those figures in and remove the raw number switch...
        
        Sorry for the frustration on this, but it can be made to work
        
        Mark Jones > Steve Cain May 24, 2014 at 6:46pm
        
        Thanks again for your help Steve. I have it performing on the bench as per the RSSI extremes , that being the 900/1600 pwm metrics. I flew it this afternoon and experimented with the RSSI failure points by putting the EZUHF into attenuation mode ( switching from hi to low power while holding the bind button down ) and then flying out low (400 feet )about 1/2 mile in auto mode. The rssi got to about 30%, but did not trigger failsafe. I found by gripping the EZ UHF antenna with my hands at the 3,000 foot mark, , I got the rssi numbers up to around 50 to 60%, and around at 65 percent DID trigger failsafe. I repeated it three times , and would say 65 percent is where rssi is going to indicate failure. I will try , as you suggested, the link quality metrics tomorrow and report my findings. Thanks again for your help !
        
        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.
    - Steve Cain 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

of 3

This reply was deleted.

Activity

Jose Araujo liked Jose Araujo's profile

spencer harvey liked spencer harvey's profile

More…

#xg { position:relative;top:120px; } #xn_bar { top:120px; }

Hello, you need to enable JavaScript to use diydrones.

Please check your browser settings or contact your system administrator.