I'm running the APM2.5+ with Arducopter 2.8.? (The version before 2.9)
My Radio is a Spektrum DX8.
All of the radio calibration went fine, but I noticed at the time of calibration that the throttle 'green bar' would randomly blip up to half throttle (or if it was at half it would blip up to full).
At the time i thought maybe it was just because i was inside and usb tethered.
Motor testing without props though verified that occasionally the motors would briefly double speed then drop back to idle or half speed. this was random again, no pattern, once every 5 to 15 seconds.
Fool that I am i thought maybe somehow attaching props would solve this issue, but again, at idle the motors would pulse enough to just lift frame, or if I was almost at takeoff speed the frame would jump up and flip.
I've noticed one issue of uneven thrust front to rear which I think is due to different quality props (front coloured ones appear stronger).
But the throttle pulse/blip thing is my primary concern.
Has anyone else experienced this?
I saw a thread somewhere about flashing the 32u chip to help it keep up with the high speed of futaba 8 channel sets, would the same fix help me? I am only skeptical about that fix due to my board being so new surely it has the latest file in the 32u chip? (The post about the flashing was from 2011).
I've ruled out the tx or rx being the issue as the motor speed is completely stable and constant when powered directly by RX,
SOLUTION (SO FAR)
Changed data rate to 11ms instead of 22ms, the throttle blips have disappeared in the 5 min test i did in the workshop, more tests tomorrow to get conclusive results, but it's looking great so far.
Many thanks to J B for suggesting this fix.
The blips during calibration might suggest an issue with the transmitter or receiver...
Have you checked the channel monitor on your DX8 to see if the transmitter is sending out a faulty signal?
I have the DX8 as well. After unspoken headaches and a couple of crashes, I found that my transmitter was occasionally sending erratic values on the elevator and aileron channels (-70%!). Luckily, my controller was still under warranty and Spektrum replaced it promptly.
Hi Peter, thanks for your prompt response.
After reviewing the monitor (which I only now know exists thanks to you) all the channels appear to be behaving.
As mentioned towards the bottom of my initial post, when motors have been run directly via the RX (and ESC of course) this issue has not been present, which is why i suspect it's an issue on the APM side.
I'm going to replace the APM board with a KKv2 tomorrow morning and see if the issue is present on a KK controller also.
I'm going to move this over to the main forum.
I really hope is not the RX as there is no way I will get a replacement unit in reasonable time, well, unless the shop I purchased it from is feeling charitable to help anyway.
I think I will still run the test with the KK v2.0 board to see if the issue is replicated with it also.
Well I just remembered I have a spare 6ch RX in the workshop, so I connected that up with the same TX and what do you know? Smooth throttle response with no blips.
This doesn't totally confirm to me that the 8ch RX is the fault though, It could also be the APM2.5 having issues with receiving 8 channels
Hi Charlie, what is the firmware version of your DX8 TX? Mine is 2.06. I also have bizarre behavior with Aux1 channel. Channel THR (Throttle) is ok for me. I watched the channel monitor as Peter suggested and I don't see any glitch... I'm using Spektrum AR8000 Rx. Anyway I will follow this post carefully. I did not have time to investigate further but wish to resolve this. .... anyway no fly zone here.... it is freezing -28 celsius... so I guess it is time to do some workbench work :). The reason I'm asking the version of your firmware is because I not sure if my problem started when I updated it recently... I will try to revert back to the previous firmware version over the weekend.
Just a quick note: in order to see your version firmware you need to keep pressing the roller when powering on the TX. Go to "System Settings" and click next until you reach your serial number. Version is at the bottom of the screen. Thx Charlie for your post.
i just bought my apm from 3dr andd tried flashing chip but cant get usb to connect to chip like wiki says so im stuck with the blips....
seems this issue is ignored?
mabye bad batch?
cant believe 3dr would not flash these to work with a super popular futaba t8j radio?
I would be reasonably unimpressed if the APM2.5+ was at fault, the precise reason I bought it from DIYD was not for lack of options but a recent bad experience with a cloned CRIUS AIOP.
i have been able to flash the ppm firmware now... will test soon
Please keep us posted on the results. Notice that you are using a Futaba radio but might resolve Spektrum also... who knows??? ... quick question: how can I see what ppm version I have on my APM 2.5 board?
I experienced the exact same problem that you are describing. I was able to make mine go away by changing my receiver to operate at 11ms. (It was set to 22ms for some reason to start.) I also experienced the same glitches on other channels. (3, 5 and 7 to be precise.)
I found that if I moved my inputs around the glitches followed so it is definitely something associated with the receiver.