Px4 Testing

I am starting this discussion to post information for  testing the Px4 platform.

Most of the discussion is currently in the APM vs Px4 thread. ArduCopter on the Px4 is a work in progressand has made great progress. I have Arducopter on a Px4 Fmu board hovering now and I am very glad to see the code base integrated into the Stm32 platorm. Ardupilot represents many hours testing and refinement , many thanks to Andrew Tridgell ,Randy Mackay  and the other developers as well as Gary Mcray for the documentation  on the Wiki

The Px4 can support a Quad with 4 Motors using only the Px4_FMu board with some of its Usart pins defined as Pwm outputs or using the Px4_Io board to supply Pwm motor (servo) outputs. The configuration with the Io board may work better at the moment , the Fmu only has a number of issues to get booted up  configured and running. It may be that all the testing at the moment is being done with boards that use the Px4_Io.

The Px4  usb is software driven not a ftdi chip like the Apm and has given problems but is working now . When the Stm32 bootloader starts it creates a Usb port with its own Id and sets up a DFU device for loading. If no bootloader request is received it jumps to the code startup and creates a usb serial port with a different USB Id for a mavlink connection. Windows drivers have to deal with the Usb connection and connect the appropiate driver.

I think the Px4 vs Apm  answer is that it is still early in the Px4 development but shows great promise.





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  • @chester, i tried setting the battery voltage to actual voltage on the battery using MP. but when i switch the tab the figure resets  to '0'. this is when selecting 'Px4'.

  • Admin

    Hi All, 

    I have been experimenting with my full up PX4 and have found a possible issue when using the USB to power the full up PX4.

    When powering the full up PX4 through the USB connection I have been using a powered USB hub and for good reason. If I try to power the full up PX4 with just the USB connection, it will not communicate with the MavLink connection though all of the leds appear as they should.

    When powering the full up PX4 with a powered USB connection I can communicate with MavLink with no problem. However the GPS number of sats will drift all over the place from 0 to 5 and back down to 0. A measurement of the voltage being supplied to the GPS indicated an out of spec 3.96 vdc.

    When powering the full up PX4 with a battery though the power converter, the GPS will get a solid lock of 7 sats or more indoors and the voltage supplied to the GPS is around an in spec 4.95 vdc.

     When I say full up PX4 I am including the FMU, IO, GPS, Spektrum PPM R/C satellite receiver, and outboard compass. I am supplying the power converter with a 7.2 vdc NiMH battery.

    When powering the PX4 with a battery through the power converter I do not feel that 4.95 vdc is sufficient as it does not leave much margin.

    Has any other member experienced this phenomenon? 


    TCIII ArduRover2 Developer

  • PX4 is cool and seems much more powerful, but I don't understand: what is the official 3DR roadmap for this boards?

    APM 2.5/2.6 now looks like the complete solution: it have the case, new compass at 2.6, etc. Improving 2.6 seems strange btw, Atmega CPU resources seems finished, why outdated board is improving?

    But PX4 looks like beta, it don't have a case, does not support PPM receivers. So, what will be next? New PX4 hardware revision with more pins, normal looking case and external compass? Or there are no plans for this? 

    Is it useful to buy PX4 now, or its better to wait a new one? All modern controllers are using powerful CPU, even 100$ Rabbit have STM on board :) Spending money for Atmega boards seems useless in 2013, but PX4 don't looks like a board, that end-user will want to buy.

  • Hi all,

    I just recently upgraded from my APM1 to PX4FMU+PX4IO. I experienced no issues installing firmware, as long as I use the Qupdate program. No success yet with MP.

    After all firmware is installed (FMU and IO) the board connects to MP without any problem. All sensors are shown in the MP-hud. Logging on the SD card shows no bad things.

    Now, when I try to calibrate the radio, it updates the green bars only every time I turn on the radio. After that, it doesn't update anymore.

    My radio is a futuba F-14, receiver FP-R118F which I modified to deliver the PPM signal. This used to work perfectly on the APM1. As far as I can see, the signal is like it should be. Attached is the signal on the PPM input on PX4IO. I power the PX4 with 12V, power to the receiver is 5V.

    I did a search, but couldn't find anyone having the same issue, it appears like it just should work..

    Any clues are much appreciated!

    Regards, Frank


  • Hi,

    I run ardupilot software on a px4fmu + px4io on an hexa with no problem on following modes : stabilize, alt hold and loiter. I wanted to try the guided mode but I run into problems. I programmed it on CH5 and tried it with a GPS lock and a working telemetry link. Whenever I switch to guided mode, the copter noses up with a pitch of about 30 degrees and rapidly moves backward and loose altitude. I didn't keep it in guided mode too long because I didn't want it hitting the ground or having it flying to far away, maybe I left it in guided mode for 1 second or two. I didn't have time to place a dynamic waypoint on the map. Shouldn't it loiter when switched to guided mode waiting for a waypoint ? Loiter works perfectly just before or just after switching to guided mode. My APM version is the latest stable for PX4 hexa. I flashed it this morning. I had the same behavior on guided mode in previous version (mid-june release candidate).

    Any idea ? Does anyone has the same behavior ?

    Best Regards,


  • Testing a new frame layout and fitted 1306 motors, it now hovers at 30% on 2s1A which is great cause I intend to add micro fpv gear asap ;)


  • Anyone got issues with prearming ? It keeps thinking radio is not calibrated and won't let me arm, but radio (and everything else for that matter) appears fine. I'm using frsky ppm rx and tried 3.0 and 3.0.1 with no luck. Any similar experiences ?

  • I am new to the px4 world but long term successful user of apm 2.5 + FW v3r1 on 2 win7 computers..  I am not able to consistently connect the px4fmu+px4io to MP1.2.59 with MP (tho it has connected only 2 or 3 times with many tries) .. It seems like it has been a hit and miss with many users.. I have seen all the posts and tried the fore-mentioned tricks to get it working..

    It connects right away with QGround Control for the iMac with no problems.. Is there a fix out there? 

  • hi chester can u pls inform a brief of getting battery voltage on mavlink on PX4. or can just give the link.

  • Developer

    I'm not seeing much activity from PX4 users over on the AC 3.0.0 release candidate testing page.

    APM Copter 3.0.0 will be the first release to run on PX4.  I have flown it and many others have flown it on PX4 but it would be great to have some of you testing it as well.

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