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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It doesn't sound like it was a sync issue. 

Unfortunately I can't read that bin file (I'm not sure if it's corrupt or didn't upload properly.  Can you please zip and attach the .log?

Thanks for the reply. I've attached  the log file.

Any help is greatly appreciated! Thank you.


I am sitting with the Hexa and Afro 20A ESC and expiriencing this same issue.

Is there any "consensus" about the problem and a common solution? 

Is latest SimonK firmware working with Afro ESC with Pixhawk?

Will reflashing ESC with BLHeli fix the problem ?


My guess would be there are between 120,000 and 150,000 Pixhawks happily flying around while connected to Simon K ESCs.

Wiring your ESC correctly to the Pixhawk fixes the problem.

ESC compatible with Simon k are not compatible with bl heli chips are differnt on PCB . This is a known issue one way to test to see if really sink issue do compas mot test all motors should spin at the same speed if not get rid of Simon k ESC try BL heli .

Craig and OG, thanks for quick reply.

Actually what I though was a problem was not really a problem with Sync or rather no problem at all. What happened was the following: when I draw up the throttle stick not all the motors started to spin at the same time, some sort of delayed on 1-2 motors till I draw throttle bit more. Then everything works perfectly fine. I had a 15 minutes nice flight, no issues at all!

Therefore I confirm that the latest Afro 30A ESC with SimonK bought one month ago from HK are compatible with Pixhawk on Arducopter 3.2.1.

My first post in this forum, as I am now just about to give up on my Pixhawk project...

I have the exact same problem as Xoltri.

I had my Pixhawk for about 7 months now, and still not beeing able to get it off the ground. 

This guy on Reddit describes the problem I also have, and it sound very much like the one Xoltri have (has?)


Quote: "...SUDDENLY all the motors went to full power. No grinding noise anymore. I closed the throttle but nothing happened it was stuck wide open. I tried to disarm but it wasn't responding,"

Specs on my setup:

Pixhawk from Hobbyking, with the newest 3.2.1 firmware from MP.

Sunnysky X4108S-14 KV 480


4S 5000 mha

It feels like it will not take the throttle, and the suddenly above 50% it goes crazy... I have managed to get it in the air 1 time, this is after I set RC_SPEED to 100, but it is no where easy to get up, and I must admit, I am a bit afraid of those 15" carbon props on a machine I cannot controle.

I have followed all the official guides out that, calibratet motors, ESC's compass etc. 7 or 8 times now and still no luck.

Can anyone help me on this problem?

I trying to use these RG ESCs with just the signal wire (one of them has the ground and it is connected) and i cant complete the ESC calibration and the PixHawk aways ARM but sometimes de motors spin sometimes not.

I'm not sure what is the problem. The other 3 ESC grounds missing or something in the BLHELI values that compromisses it.

Simon Kirby responded to my youtube video with the following:

Hi, all! It turns out that the pixhawk (http://3drobotics.com/wp-content/uploads/2014/02/px4fmuv2.4.3_schem...) uses TXS0108 buffers on the motor PWM outputs. This is a bidirectional buffer with edge accelerators, which in combination with the 220R in series with its output, means that the holding impedance of a static output signal is significantly less than with some more simple (no ESD protection) flight controllers. This means that other noise sources such as from the power wires may more easily induce current in the signal wire, and the 3.3V signal margins versus the 5V ESC MCU may cause some interesting oscillations (as seen here). You may find that simply twisting all of PWM signal wires (with their ground conductor) will reduce the inductance from the power wires enough to solve the problem. The worst case would be non-twisted power wires running beside non-twisted signal wires for long distances (so this problem may also happen more easily on larger crafts). The problem will exist regardless of software (other than its impact on current), but ESCs with ATmega8 (as opposed to ATmega8A) seem to have lower I/O transition voltages and so leave more margin for noise. The best solution would probably be a fully opto-isolated signal input ESC (not currently available for the Afro) that can deal with noise in the signal (by ignoring the offset applied to both the PWM and GND wires). Not to be confused with "OPTO" that merely means no BEC is present. These can be difficult to find sometimes because of this. Please let me know if this does or does not fix the issue for you!

Just wanted to post this so the info didn't get lost.

So basically this confirms that the combination of Afro ESC and Pixhawk is a no-go due to hardware incompatibility? The Afros can work with other flight controllers, and the pixhawk can work with other ESCs, but combining the two is a crash waiting to happen unless you use twisted pairs for the power wires and the signal/ground wires?

Are there any 30A ESCs available that can be flashed through the servo connector like the Afros, but are not susceptible to noise?

Would it be practical to modify Afro ESCs to include something like this?


Or would it just be better to seek out new ESCs? I don't want to risk a crash, and I don't want to twist my wires as that would require more wire length to compensate for the twist, and add weight.

I am flying pichawk with afro slims (essentially afro30a)  for more than year now without ever experiencig sync issues. Just make sure you have latest SK on them or BLheli runs both. About 6month those were flown with 380kv motors and 1555 props on 4s, and about 6month the same ESCs been moved to a different copter with 2216 800kv motors. But yea, I always twist my cables, that's just a general practice to prevent noise from ESCs radiating off the signal wire... 

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