Pixracer Feedback Thread

@Sn0west use the settings from the QAV250 (which are here) but make these different:

  • MC_ROLLRATE_P = 0.025
  • MC_PITCHRATE_P = 0.04
  • MC_ROLLRATE_D = 0.001
  • MC_PITCHRATE_D = 0.0005

Let us know what you get then.

Hi all, Iā€™ve got a rig going with the following setup:

  • Blackout Mini H
  • SunnySky X2204 2300kv motors
  • FrSky X8R receiver
  • RCTimer M8N GPS/Compass on a shortened (down to almost nothing) MRM mast

I have been testing over the past several days but today was the first really smooth test flight. I did add baro foam between the board and the frame plate, but otherwise the Pixracer is hard-mounted. I am using the PX4 QAV250 defaults for the most part. ESP8266 is very nice to use in lieu of the usual 3DR telemetry radio.

The only thing I havenā€™t finished up is the telemetry display on a Taranis running the latest OpenTX. I do use battery telemetry as a rule so I have that on the smart port as well.

Again, wonderful work guys!

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When I have had uBlox issues and I know everything is wired correctly. I open uBlox uCenter and reset the GPS to defaults. Connect to the Flight Controller and boot. The Controller detects and configures the GPS as it requires.

It turned out to simply come down to weather, my working location, and the tight airframe confines. Now with the GPS on a very short rigid mast it fixes just fine when outdoors. Iā€™ve been working with GPS while developing products for years but there is always more to learn!

I do have one of the RTFQ GPSā€™s on the way as well but that might just end up on another Pixracer :slightly_smiling:

Cheers.

It doesnā€™t work at all.
The default values in qgc do not match the list you gave me for qav 250. Strange isnā€™t it?

Here the screenshot of the values I tried.

The value MC_PITCHRATE_D = 0.0005 dose not exist.

Could the problem be a esc problem? I use bheli opto 20 amps with simonk firmware on it.

and my motors are tigers
I could flash them, but I never did this so I would need advices what values to change or what firmeware to use.
If nothing helps I will take it apart and rebuild it from scratch :grin::unamused:

I use qgc 2.9.2 and the master firmware.

Are you using the wifi for your connection to the ground station while flying, or just for programming it? Have you done any range testing w/ the ESP8266?

I havenā€™t range tested. Iā€™m a little careful flying since it is winter here and there is a lot of snow on the ground. I will say it is crazy the range those little chip antennas can get even just around the house!

Just wanted to say that I managed to get rid of my vibrations. So I just tuned my pidā€™s in my basement, I have no ideas hoe it would fly.
Anyway Iā€™m glad that Iā€™ve fixed it.

Here are my settings. Just for the very basic basement setup.

I built my copter today, and sameā€¦ It was oscillating wildly.
Sn0westā€™s basement params got me in the air.
Motors are KDE 2304 2300 with 6x3 Graupner C-Props. Running on 3s.
Sn0west, please post any updated params, when you do more tuning.

Iā€™m very confused by the flight modes, too. Coming from APMā€¦
Is this normal for px4?
Safety switch was non functional. Lights solid when I power the copter, and no need to press it.
I canā€™t arm or take off in any mode other than Manual. I can switch to altctl in the air, but thatā€™s difficult.
And, I canā€™t disarm in altctl mode!! This one was disturbing. I held the stick bottom left for a while. The props were not spinning. But, when I picked it up and it went unlevel, the motors jumped to life! If I switch back to manual, I can disarm.
Should the motors slowly spin when the throttle is down?

Is there a previous forum or manual with more info on configuring px4?

thanks for any help!

Ha Iā€™m glad I could help someone :slight_smile:
But as I said those values are not reliable and Iā€™m not sure how they behave outside! I need a lot more time into PID tuning.
The stock PID are for biger copter with less thrust than race copters with powerful setups.

I never got a answer if there will be a way if tuning PID in the air with a nobe and a switch like in cleanflight. This would make life way easier.

Ther is a kill switch (RC_MAP_KILL_SW) this will stop all your motors.
I also would like to have a arming switch and that the motors are spining but I did not find out how to do it. I think itā€™s not available at the moment.
Imagine you are at a race and the at the start you need to arme with sticks. Until you get in the air your opponents already finished the first lap of the race :wink:

And also here, I never got a answer, armingyour copter in a other modus than manual is apparently not possible, unfortunately. I would love to arm in acro modus butā€¦no chanceā€¦

Does your ā€œsafety switchā€ work?
I thought maybe px4 didnā€™t use it.
But, I put APM on my pixracer, and still, the safety switch light immediately lights solid red, and I donā€™t have to press it. Usually it flashes until it is pressed.
Iā€™m not sure if my switch is broken, or maybe its behavior is different on pixracer?

The safety switch is currently ignored by the PixRacer. What is your preference? Do you think itā€™s necessary, or that the arming mechanism is sufficent?

Thanks!
I donā€™t think itā€™s necessary. I just wanted to be sure there wasnā€™t something wrong.

Have any of the Ardu or PX4 devs taken the advice of others (like peabody124 of TauLabs) and got the OneShot stuff working yet? For a ā€œracerā€ board, even if you refute its use, the ability to enable is a game changer for some folks.

What is the status on: ā€œOneShot PWM output for new ESCsā€?

ā€œHere you can see the latency from an update from the gyro (MPU9250 IRQ) to the completion of the pulse is about 300 Āµs, which is much better than the several milliseconds with traditional asynchronous PWM.ā€

Px4 supports it. Arducopter probably will in the next major release.

Can you link the relevant info for setup? I didnā€™t jump out at me on Google.

That was tough to find! (Iā€™m not being sarcasticā€¦ it really was)

https://groups.google.com/forum/#!topic/px4users/UWPFu9XuKzY

  • Support for OneShot outputs (set PWM_MIN to 150 and PWM_MAX to 250 to get there)

I have lost the ability to connect pixracer to QGC 2.8 while using the the setup panel for the ESP8266 WiFi Bridge when I changed from 921600 to 57600 baudā€¦ QGC should be able to pick up the UDP link on boot up using 57600 so that I can use the setup panel to go back to 921600 and hopefully reconnect to QGC? So far I have had no luckā€¦ What am I missing?

So Iā€™ve just managed to test-hover my QR400 for the first time. No issues to report, everything seems to work as advertised - except that it doesnā€™t really keep to ā€œPWM_MINā€ value. At idle throttle, giving roll/pitch/yaw input speeds up one respective pair of motors and completely stops the other, whereas I would expect the ā€œthrottling downā€ motors to remain at PWM_MIN and keep spinning. But I donā€™t think itā€™s a big issue, and it shouldnā€™t present itself in normal flight. (Before anyone asks: yes, the ESCs are calibrated properly - the lower PWM threshold is set at 1150 in BLHeli, and PWM_MIN in PX4 is set to 1175).

Iā€™ve used the QAV250 preset. The frame is a Flyduino QR400 using Tiger MN2213-950kv motors, T9545 props, Littlebee 20A ESCs and a 4S Lipo. No oscillations or anything to report, stock PIDs seemed adequate (though the 30 second long living room hover is not much of a test).

Try the latest build of QGC: 2.9.2 is working well for me at 921.6K baud

It worked for me too at 921600 until I changed it 57600ā€¦ I just donā€™t know how to get back to 921600ā€¦