I have been trying to isolate an intermittent servo twitch the last couple days. I have the APM 2.5 in an X8 running ArduPlane 2.68.
I have power going to the output rail with a 5V Castle BEC.
The twitch is very random and fairly small deflection. In manual mode if I slowly move the elevator or aileron stick I can get it to do it, just not 100% repeatable.
I have flown the plane a few times. I tested stabilize mode and it worked great, but while flying in either manual or stab mode the plane will twitch randomly as if a side gust hits it.
I started removing components one at a time to see if it would stop. I pulled out the BEC and have been using a JR 4.8v receiver pack for the rest of the testing.
I was down to just the APM (no GPS, telemetry or airspeed connected) and the Futaba receiver. It still did it. Straight out of the receiver it was OK.
I tried a new APM loaded with same firmware and I got the same results.
I have tried both analog and digital servos from Hitec, JR and Futaba.
I had the same APM in my Skywalker and it did not have a twitch. Only change was to add a airspeed sensor and elevon mixing when I installed it into the X8.
Just disabled the elevon mixing in the radio and the APM. Same results
Just tried another Futaba 8FG, calibrated it and same results.
I just remembered that I had a DragonLink through a JR9303 radio on the other Skywalker.
Swapped out to a Spektrum DX7/AR7000, calibrated and twitch went away.
OK, so now I need to find out why the Futaba is causing a twitch. I am using the Futaba R6208SB receiver..
I will try a couple different rx's to see if that changes anything.
Before I swapped receivers I changed the output to MULT vs MLT2.
MLT2 mode enables channels 9-12.
That did not fix it either.
Tried a R617FS receiver and no more twitching!
This requires changing the "frequency" screen from MULT to 7CH
Any ideas what is changing in the Futaba radio to cause a twitch when an 8 channel or higher receiver is used?
Replies
Actually I had that same problem over the weekend when I tried to update the driver software. I've added some instructions on updating the 32u2's driver on the wiki.
I talked with Craig and the APMs are still not shipping with this new ppm encoder but should start in the near future.
Got it flashed. Found more info in another thread. Had to load the USB driver from the Flip software. Now I'll see if the twitch goes away.
Followed steps but I am getting a DLL error when I select USB.
Ah, this problem is well known in arducopter-land. I think you need to update to the latest ppm encoder.
Here's the trouble shooting guide entry including a video with before and after upgrading the ppm encoder on an APM2.5 mounted on a big-ish hexacopter.
Here's the guide for upgrading your ppm encoder for arduplane.
I noticed a twitch when I moved from direct attach to the Futaba RX to using S.BUS. Long story short I wanted my RX out on the wing.. When I reduced my travel from 100 to 75 in the menu and re-calibrated the twitch went away. I noticed my twitch was induced by slowly moving the elevator servo. The ailerons would twitch out.
I chalked it up as something funky S.BUS was doing. After I went back to direct attached to the Rx the problem went away. Interesting that another person is having the same trouble.