hi Folks.

I have just mounted a jdrones gopro gimbal to my stock 3DR quad and have a strange twitch on channel 6 for the pitch control.

When sitting on a desk, the pitch twitches once every few seconds (less than 10). If I look at the radio input I can see the twitch there most of the time but only if there are a few twitches in quick succession. A single twitch hardly shows compared to quick succession where it goes almost full scale.

If I look on the radio (Spektrum DX8) the monitor output shows nothing. Oddly, the tuning graphs also show nothing for channel 6. When I flick the switch between the three positions the graph moves as expected.


Finally, I put a spare servo directly onto the receiver channel 6 and no twitch from it. Nudda. Zip.

So, radio says there is no twitch. Server connected to the receiver shows no twitch. MP tuning graphs shows no twitch.

Radio input on setup shows twitch. Pitch servo for camera responds to twitch.

if I swap to another channel, the problem goes away...

Really confused. Any help please :)

Latest 2.4.1 firmware loaded onto APM 1 (2560)

Ch6 Opt in MP is set to  CH6_NONE



Views: 1562

Reply to This

Replies to This Discussion

Hi Randy,

No, I only have an APM2 (my first)...   (most of my embedded stuff revolves around the rabbitcore)

I have not got to the coding part as of yet, but that is my goal, so there is no time like the present...

hook me up and i will test on the weekend...

Thanks for all your work on this project...   its alot of fun for us!


Corey, Airmamaf,

     I've just put a version 2.6-Beta in the downloads area.  I'm unable to reproduce the twitching..it all seems to work fine.  It's an experimental version so be careful..but it's possible that I inadvertantly fixed this bug when I did the motors refactoring.  It's possible that the twitching was being caused by interference with the previous motors code.

     Could you check it out..maybe just a bench test 'cuz the Beta code is not fully tested (although it's probably ok).

Check if this: http://code.google.com/p/ardupilot-mega/issues/detail?id=508 seems to be related.

I've seen noisy output for no reason.

Thanks Randy, I don't know when I'll have time to test it, because after a hard crash, I had to send back my board to get repaired.

Thanks Randy,

I am going to try it and see if it helps.   :)



Just an update,

I have everything setup and ready for testing.  Got my first compile done, and have the beta firmware loaded.    The bench test went well, with no issue reported.     I have found that on my quad the problem does not always show up right away, so I am going to leave it running for a bit to see if it starts...   

In learning about compiling the source, I found the PPM encoder firmware refresh document.    Randy, do you think it may be a bad load of firmware?  Should I do a refresh?   


On the scope, the twitch seems to represent itself as a jump to a 100% duty cycle.


Thanks again for all of this great work!  


Sad to say, I did get it to reperduce the issue with the beta firmware...   Can you help me get the logs for you Randy?





     Yes, if you could try reloading the ppm firmware (if you have an atmel programmer or equivalent) that would be great.  You've probably found it but the wiki page is here for the APM1 (I assume you have an APM1).

     Just a dataflash log or tlog would be great:

      Dataflash logs needs to be downloaded explicitely from the APM (connect with a USB cable, push the terminal button on the APmissionPlanner, then click the download logs button and pick the last one or two on the list).

     Tlogs appear in your APMissionPlanner's "logs" directory (i.e. wherever it was installed).

   I agree with Andke's comments below re issue #508 (twitchy aileron) which seems to have been mostly resolved by updating the ppm firmware.  weird!

Here are the logs from tonight.    When i left it on the ground, it did not seem to happen.   So i did some indoor flight and it started...  Landed it and it did it a little more, and then stopped.    

PS, I am a apm2, So I should be ok to flash the PPM encoder...  



Hi Again,

Here is another log.  flew for a bit and then landed.    Just a bit after it self disarmed, the was one twitch..   I think I am seeing it in the pitch in log.  


I must say, Seems to be beter though...


HI Randy,

I did get a chance to reload the PPM firmware.  (I tried to load the latest for my APM of ArduPPM_v2.2.66_ATMega32U2. and it did not seem to like it.   The send-receive leds flashed constantly.     So I reverted to the original of 2.2.65... 


This did not seem to help my issue though. 

Here is a video of the issue and a pic of my rig.


Thanks Again Corey





     I've had a look at your logs and I don't see any strange twitching in the roll or pitch.  We don't log the CH6 in the dataflash so I can't see what that's doing.  We do log all the radio input in the tlogs so they might be interesting to see (they appear in your AP Mission Planner directory).  I'm not sure what the update rate of the tlogs is..it might be 10hz which might be fast enough to catch the problem.

I still think it's most likely a radio problem.  You're using a copter right?  If 'yes' can you load the "ArduPPM_v0.9.87_Arducopter-APMv1.4.hex" ppm encoder from the downloads area?

Also do you find it happens when the sticks are in a certain position?  Like throttle down and roll fully left?

Reply to Discussion


© 2018   Created by Chris Anderson.   Powered by

Badges  |  Report an Issue  |  Terms of Service