== Edit 2/15 ==
I've replaced the 2.9 APM_RC libraries with the libs from 2.8, and commented out some code in radio.pde that referenced those libraries. The issue's disappeared using this workaround so at least I can fly on 2.9 using PPM.
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I'm running 2.9 on a Crius V1.1 board with HobbyKing 30A SimonK (bs_nfet.hex) firmware. Motors are NTM 2826 1200kv motors with 8x4 carbon props. Receiver is a TFR4-B running in PPM mode.
This is all on a tricopter with an AUW of 1180g.
As the video shows - there are random power surges in the front 2 motors. For some reason the tail motor doesn't see these surges. I've verified that both front motors and escs are working properly by hooking them up directly to the receiver, so solder connections are all solid. I only see the power surges when it's hooked up to the flight controller (could there be a problem with the header pins?)
At the instruction of Aleksey - I played around with RC_SPEED which defaulted to 490hz. I tried 400hz and 125hz. Lowering the refresh rate to 125hz actually made the defect larger. It surged harder and longer before it caught itself and settled down to the right speed.
At this point - the only thing I can think to do is swap out flight controllers - but that's going to take some time. I thought I'd throw this out there to see if anyone's ever seen anything like this.
I'm attaching tlogs from both a flight and the most recent bench run. My board can't do raw sensor captures, so all I have is whatever standard telemetry gives me. All I can tell from the logs is that channels 1 and 4 go high and low at random intervals.
Replies
I solved the problem when I changed transmitter FRAMERATE from 22ms to 11ms (better described few posts above).
Is this an interesting findings in the work to try to permanently solve the problem?
I've never even seen that board before. To be honest, I wish all the people selling the clones would also contribute to providing support. it's hard enough supporting the 3dr hardware let alone the clones :-(
Just swapped out the RXs with a known working one. Same issue.
It looks like that PPM encoder issue the dev team recently released an update for, but in my case - I don't have an easy way to update the Crius.
I'll reach out to Aleksey and see what options I have (short of swapping back to pwm). I'll start prepping up that Arduflyer in the meantime.
I had exactly same symptoms with APM2.5 and 2.9.1. Using Spectrum DX8 and PWM. I think I have solved the problem when I went to the Transmitter SYSTEM SETUP menu and changed FRAMERATE (from 22ms) to 11 ms. Have tried a lot of times now without symtoms. I dont know why it work, but when I set it back to 22ms, the symtoms start again.
Lito,
You're getting glitches in the radio input to the APM so you're on the right track with the suggestions to swap out the receiver or upgrade the ppm encoder. Below are roll (ch1), pitch (ch2), throttle (ch3) and yaw (ch4) and you can see that even though you weren't touching the other channels in your tests (assuming that the tlogs are taken at the same time as the test) you're getting jumps in the roll and pitch as soon as you raise the throttle above zero.
Our ppm encoder couldn't handle the update rate of the new, very fast futuba transmitters which have over 8 channels so I'd upgrade that first. It's also possible that the ppm receiver you're using can't read the futaba updates quickly enough but I'm less sure about that.
This was a problem with Futaba RX and there was an update for the PPM encoder in the Ardu. Since you are using a PPM signal I'm not sure its valid however you might want to review this problem and see if it solves your issue
http://code.google.com/p/ardupilot-mega/wiki/APM2Encoder
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