H8 Configuration


I will shortly be staring a new multirotor build and will be building this as a H8 running 8 motors.

As there isn’t a config for a H8, should I run this as an X8 or do I need to learn how to modify the source code and modify the motor configuration?

I ask as I had a TBS Disco which I could not get to fly with the Pixhawk as the arm angles seem different to those hard coded in APM and it quickly goes out of control. The same Pixhawk mounted to and X-Frame of similar dimensions works great so it’s not a hardware issue.


Can’t help with the 8motor config but regards your Discovery do you have any logs? I run a Pixhawk on my Discovery (using V style frame rather than X) and she flies perfectly at slow speeds all the way up to 20m/s (42mph).

Hi Mark, Thanks for the reply!

I have read that people have Disco’s flying with Pixhawk but just never got mine to. I have 2 Pixhawks. When I initially had issues with my 1st Pixhawk in the Disco, I put it into an X Frame and it worked great. I purchased the 2nd Pixhawk, put it in the Disco and had the same issues as the 1st one.

I have tried both X and V frame modes but both modes had the same issue. I also tried downloading the IRIS settings but every single time had had the same issue. The Disco would hover OK but as soon as I moved the sticks to roll or pitch she would oscillate violently and crash.

I have posted 2 logs up to the following locations:
drive.google.com/file/d/0B-OjZI … sp=sharing
drive.google.com/file/d/0B-OjZI … sp=sharing

I do hope you can shed some light on this as I’d love to get my Disco flying. I will still be building the H-Frame as well so if we can get the Disco working I guess I’ll have to go and buy a 3rd Pixhawk…The missus is gonna luv me…not…

Thanks again!


I’ve compared your parameter list to mine and can see some differences.
Try changing the the settings to these, as your desired pitch and roll are well behind the actual pitch and roll they should be able to sharpen up the Pixhawk control on the frame.

Be careful though as my frame is 2kg with 1000kv motor’s and 10x5" props on a 4s. Depending on how far away from that spec your is you may have to adjust the parameters slightly, but if she will fly OK in stabilise and AltHold then you should be able to do an Auto tune to dial it in.







I’d also turn EKF on as my Disco just “feels” smoother with it.

Thanks Mark.

If the weather is good on Saturday I’ll dial in these settings and give this a try. I’ve tried settings similar to this previously but wiil definitely try again. (Have never changed MOT_TCRV_MAXPCT though.)

To Turn EKF on - Is this setting AHRS_EKF_USE = 1 ?


I would use x8. H and x is a quad thing. The quad only has one motor per arm obviously, h4 us to get around a frame torquing issue. X8 has 2 motors oer arm so yaw torque is ideally none unless yawing.

That is the correct ekf parameter to enable.

sent from my phone so apologies for any typos

Thanks RabbitStu,

I’m still waiting for parts to arrive to build the H8 but will try it as an X8. In the meantime I’ll try the TBS Disco with Mark’s config. Roll on weekend!


Hi Mark,

I used your settings but my Disco did the same. It took off and hovered OK but as soon as I put in a bit of roll on the TX and she oscillated violently in roll and pitch and then crashed.

The auto analysis of the attached log is interesting as it has failed - Test: Compass = FAIL - Large compass off params (X:-84.00, Y:65.00, Z:191.00) Large compass offset in MAG data: Z: 191.00 and Test: PM = FAIL - 2 slow loop lines found, max 12.08% on line 4933

Not sure what the 2 slow loop lines means but I uploaded the latest firmware 3.2.1 and re-calibrated the Pixhawk just before flying, Accel Calibration, Compass, Radio and Compass Mot and they all passed so why it failed compass on its first flight is a mystery.

Maybe my Pixhawk has gone faulty. I’ll wait till the parts arrive for my new quad. I’ll configure it as a standard X frame initially and if that does the same then I’ll assume my Pixhawk has gone faulty and will have to return it.

Y̶o̶u̶r̶ ̶r̶a̶t̶e̶ ̶r̶o̶l̶l̶ ̶P̶ ̶a̶n̶d̶ ̶p̶i̶t̶c̶h̶ ̶P̶ ̶a̶r̶e̶ ̶r̶e̶a̶l̶l̶y̶ ̶d̶i̶f̶f̶e̶r̶e̶n̶t̶ ̶t̶o̶ ̶e̶a̶c̶h̶ ̶o̶t̶h̶e̶r̶,̶ ̶f̶o̶r̶ ̶a̶ ̶q̶u̶a̶d̶ ̶t̶h̶e̶y̶ ̶s̶h̶o̶u̶l̶d̶ ̶b̶e̶ ̶a̶b̶o̶u̶t̶ ̶t̶h̶e̶ ̶s̶a̶m̶e̶ ̶i̶f̶ ̶n̶o̶t̶ ̶t̶h̶e̶ ̶s̶a̶m̶e̶.̶ ̶Y̶o̶u̶r̶ ̶R̶a̶t̶e̶ ̶I̶ ̶n̶u̶m̶b̶e̶r̶s̶ ̶a̶r̶e̶ ̶t̶h̶e̶ ̶s̶a̶m̶e̶ ̶a̶s̶ ̶y̶o̶u̶r̶ ̶P̶ ̶n̶u̶m̶b̶e̶r̶s̶!̶ ̶t̶h̶a̶t̶ ̶d̶o̶e̶s̶n̶’̶t̶ ̶l̶o̶o̶k̶ ̶r̶i̶g̶h̶t̶.̶.̶.̶I̶ ̶i̶s̶ ̶n̶o̶r̶m̶a̶l̶l̶y̶ ̶a̶b̶o̶u̶t̶ ̶1̶/̶1̶0̶ ̶o̶f̶ ̶P̶.̶

I̶t̶ ̶i̶s̶n̶’̶t̶ ̶t̶u̶n̶e̶d̶ ̶p̶r̶o̶p̶e̶r̶l̶y̶.̶

edit ignore most of that! I am talking rubbish

I am surprised pitch and roll are so different though!


Cyclone Marcia ran out of steam and the skies cleared so I tested my Pixhawk configured on an X-Frame. The frame is stable as a rock in stabilize mode with no issues just like my original Pixhawk on an X-Frame and I can fly around with no sign of any control issues. (This is with Roll and Pitch PID set at 1200 and with the quad not trimmed)

Remove the Pixhawk and re-install back in the TBS Disco and reconfigure as a V-Frame with PID’s set as suggested for the Disco. (I also re-calibrated everything including compass and compass MOT.)

Take off in stabilize mode and hover with no wind and minimal input all OK but as soon as I try to maneuver she goes out of control, flips and crashes.

Reinstalled back in the X-Frame, reconfigure and calibrate and again she flies perfectly. So even though others are having success with a Pixhawk in a TBS Disco, mine gets airsick and will not fly.

Looks like I’ll have to part ways with the Disco and just stick with X and or H-frames.


I would imagine a disco should fly ok ish with default gains? Have you tried default gains.

sent from my phone so apologies for any typos

Hi RabbitStu,

Yup, I have tried all the available ones that come with the firmware and all variations that I have sourced from several internet forums and sources. I have also tried on many occasion to tune it manually but she just won’t fly. Tis very strange! On several occasions I was thinking it might be a faulty board but if it’s stable in an X-Frame then it suggests that it’s OK. I have reset the board as well, loaded the rover and plane firmwares to reset everything as well. (I didn’t put the X-Frame into loiter modes as I hadn’t done any flight trimming)

All my parts have arrived to build my new frame so I’ve stripped down the test frame and will now build my new frame. Not sure now if I’ll build it as a H8 and may just go with a X8 instead. Haven’t quite made up my mind but might go with the X8 as at least its supported.


Out of interest, what esc, motor, prop combo are you using on the disco? and have you tried changing those items from the X to the disco?
I’m curious if the disco’s esc’s can handle the 490 refresh the Pixhawk is sending out.