I believe I have a problem with my Pixhawk and was hoping for some help.  Also posted this on rcgroups.

The issue is that when my speed controllers are hooked up to the Pixhawk they exhibit a bad sync issue.  However when they are connected to my old APM (3.1) or just a receiver directly they do not exhibit these symptoms.  This has resulted in 4 crashes now until I just tonight narrowed down the issue to the Pixhawk.

Can anyone advise what is going on?  Here are the specs of my setup:

Afro 30A ESC's with SimonK firmware (have tried all versions, and made my own with various parameters)

Tiger MT2216-9 1100kv motors

4S 3700mah battery



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Thanks artem, quite stupid indeed! But I'm freaked out now with this quad, nothing goes to plan! Thanks again.... I tested the motors with the stock firmware, and on servo tester, it is pretty good with high impulsion, let's see now how will they perform once reconnected to the PIxhawk.... Tks again much appreciated for your great simple basic comments, I am implementing them to the letter, and minimize forthcoming problems.... Take care. Cheers and Safe Flying Lads!

Don't worry and do not panic, out of my experience most of the sync losses are actually due to the poor electrical connection of ESC to the motor or motor quality itself and only once it was a bad ESC (multistar v2 slim). Take care to salder your motor leads to the ESC than check each ESC/motor/prop with your fligh pack for sync loss on the ground with a simple servo tester.  

motor sink issues can occur when you arm your copter the motors are set not to spin up . this can occurs from time to times just power cycle the copter should be fine. also seen this occur with pix hawk using the arming button enabled motors are set not to spin up one ESC can beep late. power cycle the copter. have better results removing arming button for some reason.


Hi I had the same issue, and stripped down the copter rebuilding it now. But new to MP, and difficulty understanding the Logs. Would you mind having a look please, might i ask for guidance?

Here is the link to the file: https://drive.google.com/file/d/0B7vMeLuh3uvRNzdicDRzSm9XQXc/view?u...

Thanks for your help might you find something relevant... I trust I had a voltage drop, therefore a sync issue, as it crashed 3 times the same day on the front right arm all the time!

Cheers and safe flying Lads!

Hi Artem, I rebuilt the copter with NEW Slim 20 ESC with SimonkFirmware but still have a motor not sync on throttle start, it disappears on recalibrating the ESCs on the PIxhawk each time i arm, which is not recomforting.... I was studying the evening the KKflashtool to set the High Timing and PWM_comp as you suggested, but seriously, after few hours, I cannot find any support out there as to how to set these parameters while reflashing the ESCs with latest SimonK! Harrrr!? You've been kind enough so far with patience towards this issue; but here seriously, I would need you guidance understand which Software you are using for flashing SimonK atmel ESCs in order to set these parameters on the ESC and save them!?!? I am almost there Artem. Tks for your help and support; always much appreciated....

ditch the NEW Slim 20 ESC with Simonk Firmware ! you need BL heli compatible ESC with pix Hawk !!

It's not unexpected to invoke sync issues in autotune as autotune deliberately does lots of very sudden high throttle movement - classic way to invoke desync.

HI OG, you just replied to some of my concerns, but I could not reply directly to your post; when you are suggesting BLHeli, for PIxhawk.... Would you mind sharing compulsory settings on BLheli to get it to work properly, as with BLHeli testing many settings I gave up; as I crashed so many times with 920KV t-Motors and Afro Slim 20A ESC with BLHeli initially! Now I reverted back to SimonK and apart form one motor not spinning on arming; I recalibrate the ESCs and it flies, but not too confident.... I would rather get back to BLHeli; but I wish someone would share their settings for PIxhawk; as it is a serious headache guys!

Same issue; it costed me a Gimbal, new ESCs, changing motors, but still having issues.... I gave up on BLHeli, rebuild the copter; and now with SimonK and still having sync issue on Arming; and I have to recalibrate the ESCs every time before taking off, and it flies... But seriously not reassuring, Lads! 

I really feel desperate, especially as no one is sharing their BLHeli settings.... It's been 2 months of trouble shooting... Never had such issues on APM or any other FCs, and we have build quite a lot of Copters in the past few years; and this PIxhawk, is seriously a pain! HEELLPPP GUys, please; we are too many for it to be just us! There is a problem somewhere else; come on!?

I'm running afro 20a slims from a pixhawk on tarot 650sport.  I've recently extended it with the older 650 arms (which are quite a bit longer) so it's now an 800, with 15" props on 3508 motors.  The ESCs are flashed with blheli, and I extended the motor->esc wires instead of the esc->pixhawk wires, but signal and power lines are run together in the arms with no twisting.  I've done hundreds of flights with zero issues, except for a single flight that I changed the blheli settings to damped light/braking mode and I had a desync.  Changed it back to High frequency and not had a problem since.

My sunnysky v3508 580kv motors do screech a lot though - I read somewhere this is possibly something to do with the waveform that comes out of the afros.  Elsewhere I read this is a potential sign of a motor about to desync, but I've never had a problem with many flights except the one which is understood.

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