Pixraxer as a RACER

I want to start a thread for the pixracer as a RACER.

My personal background: I started flying with a self-build APM aluminum - wood frame quadcopter (diameter about 70cm) about 5 years ago. Then moved on to small helis and larger (600class) helis with commercial fbl. For about a year and a half I am now flying 250 class quadcopter with naze32 on them. Pure acro through gates, through trees, around obstacles and abandoned houses with loopings, flips etc. Nothing like the big shots on youtube. I would say medium flyer.

Setup: ZMR250, 12a ESC with BLHELI 14.3, 1806 2300kv DYS Motors, 5040 DAL Props. Pure FPV flying. No LOS. This rig flew with the NAZE32 with betaflight just fine. Airmode was a dream.
No GPS, no OSD, no nothing. Just a pure racer :wink:

Changes: pixracer with the latest (from 11.2.16) px4 stack. ACSP4 underneath, but just as BEC for the pixracer. The esc are soldered on the diatone pdb. I didn´t want to change this. The wifi module on top.

Impressions and wishes in the next comments.

Hardware Impressions:

This setup (ACSP4 underneath - pixracer - on top wifi module) barely fits into the ZMR! Good are the pins on the back for the esc. This is a major drawback on the NAZE. But why is the power cable between ACSP4 and pixracer on the right? Everything that sticks out on a side is prone for a tear off.

Software Impressions:

I am just adressing the RACER view in the pixracer!

I used the stock QAV250 settings.
I am flying ACRO only. After now 5 packs trying to fly with it I must say it is not flyable at all. Arming in ACRO isn´t possible. Why not?
In ACRO if you let it hover, it all of a sudden rolls or pitches to a side. There is no certain pattern to it. While flying, after a while it suddenly drifts to a side (back forward lef right - you never now).

Therefore I haven´t tried to do flips or anything. I was just struggling to keep the rig in the air.

I am more than willing (if the weather permits here in the northernmost part of Germany) to try to tune it. But where to start with which parameters?


  • Arming via switch - yes I know that there is a kill-switch an it works on my setup.
    • In ACRO it has to be rock stable. When you put the copter in a certain angle, the fc hast to keep the copter in that angle unless a stick-command via the transmitter is given. Every FBL on a heli does that, not talking about the NAZE.
    • Auto-Tune would be great. With my old APM 2.6 and Ardupilot copter on it, it works great. GTUNE in baseflight is great.
  • Low throttle like the airmode in betaflight would be nice, but first a stable behaviour in ACRO.

Gunnar, thanks for the report. I’ve recently observed the same problem with Acro mode that you describe here, and I’ve filed an issue to track the problem down.

Yeah, my experience with Acro has been similar so far. Not happy at all with the current state of the implementation.

We’re not going to pretend we’re racing experts (yet), so if you know developers who might be interested in this board / ecosystem (with a larger development community and things like Wifi behind it) - they would be very welcome.

Meanwhile we’re trying to get up to speed as fast as possible and Mark is making some very good comparisons of what we achieve right now vs. the state of the art, so I have no doubt he’ll fix this for good.

If I could also add somethings from my wish list

is first the ability to choose between two or more different PID controller. It depends if I fly a race, if I fly freestyle or I attache a mobius/gopro to my frame.
It would be nice to be able to choose easly (by stick combinations) the PID’s that I just need.

Second on my wish list is inflight tuning of PID srttings. A nob and a 3 way switch add/nothing/sub over osd would be nice but not a major request.

Third wish on my list is a blackbox to be able to see where I could tune my copter a better way.

Yes all these features are in cleanflight/betaflight and would be awesome to use theme here as well.

What I miss is a better documentation of all parameters in px4. What they do and what are they good for. Did I missed that?

Thanks, this is very helpful. We have worked out how to fix the acro performance and an update is in the works for today.

It would be fantastic if you could help us with flight testing these new settings:

To find these parameters, go to the param editor (bottom menu item in the setup screen), the click on Tools -> Search

We will also provide screenshots to make it easier.

i have much better acro mode behavior of my Spedix S250AQ with these parameter changes:

The first one is critical, and increasing P and I gains improved the “heading lock” feel.
Let me know if this brings acro mode up to par for you, or whether you needed to tune the PID gains further.

I will test again as soon as weather permits. Sadly not the case this weekend, according to the forecast -.-

It will be great to get your feedback on this, and I hope that forecast is wrong.
May I ask how you modify parameters for PX4? Do you use QGC with a wifi connection, or some other method?
And have you tried the “Set to RC” feature to adjust gains from your TX?

I tried using QGC from an Android tablet via Wifi (ESP8266 on the Pixracer). That worked well enough for basic calibrations in the workshop, but the connection quality at the field was really bad, and it reported “vehicle failed to transmit full parameter list” and didn’t allow me to adjust anything as a result. As posted in the other thread, I suspect that was because the PX4 firmware was a couple days old on the Pixracer, and QGC on the tablet probably auto-updated in the meantime.

Haven’t used “Set to RC”, wasn’t aware that the option exists in PX4. Will check it out, having some pots/sliders for inflight value adjustment can be really helpful.

I have an old google Nexus 7 from 2012 and despite it having the GPS chip broken in it, it works good with the pixracer.
I just flashed the new version and set everything as noted above.
I hope there will be a chance of flying, because the forecast here in Northern Germany (Flensburg) is very bad with rain and wind 5-9BFT.
By the way, how do I know which firmware is installed on the pixracer?
Is there a CLI dump to quickly save and copy parameters to discussions?

There are two ways: You can upload a log file to http://logs.uaventure.com, which includes a param dump in the log. Or you use QGroundControl to save the parameters - that might not be available yet on mobile builds though.

Yes I know,that you can save parameters in qgc. What I want is to have a dump, that I can have a look at with e.g. notepad. Like the cli dump in cleanflight. Also uploading some parameters like in cleanflight.

QGC dumps them to a text file.

I don’t think there are currently any convenience tools to view or upload subsets of parameters from the savefiles. I wouldn’t recommend trying to use the CLI (nsh shell) load function though; just tried save/load to microSD and it seems to have corrupted my sensor calibration.

Update on loading parameters from stored file via NSH console. The warning messages seem to be bogus, my calibration parameters were not corrupted.