RCIN - RCOUT Delay on Ch3

It was suggested by a respected member of RC Groups to contact you, the developers, of an Issue I have.
Current setup of 2 crafts:

450 QUAD
20A Mini Simonk ESCs
3DR IRIS motors
PixHawk 2.4.8
Firmware 3.4.1
FrSky X8R Rx connected SBUS
FrSky XJT Tx module in a Turnigy 9x Tx modified with SmartieBoard 9xtreme

550 HEX
AirGear 350 motor/ESC set
Same FC, Rx and Tx

Since before the Tx mod, (Stock Turnigy 9x with 9X8Cv2 Rx and PPM converter) I would experience a motor shut off delay.
IE, the motors are still powered after cutting throttle.
I posted the logs for both craft in RC Groups and sure enough, they pointed out there is a delay between RCIN and RCOUT on Ch3.

The crafts “bounce” on contact during any automated landings - motors do not shut off instantly like what I see my friends posting.

Could someone take a look at the logs and see if there is any solution to this issue?
2016-11-13 10-15-40.log (888.0 KB)

This was seen with 3.3.3 firmware too.

Also, I would like to add there is a severe delay now with RCIN and RCOUT.

Add Tarot 680pro to the fleet
Tarot 4006/620KV
Same ESCs as the 450
Same FC, Tx & Rx
Tarot 1355 props
The issue still occurs with 3.4.4 on all three craft

Understood - now if I can only get the RCOUT ch3 delay fixed :smiley:

I also noted that even after re-calibrating ESCs on 3.4.1, it takes a lot more throttle to get the motors spinning. And even then, only two, adjoining or opposite, motors begin spinning before the other two until more throttle is applied.

If it’s in an altitude hold mode (which is any of Loiter/Pos Hold/Althold), depending on what your status of vehicle level is, you might see motors spin up out of sequence. Also, in those altitude hold modes, liftoff won’t occur until after half throttle.

Props will try and spin themselves in such a way to level the vehicle before takeoff if it’s not level.


There’s a 2 second delay after arming before the motors start spinning. That’s a change added for safety in AC3.4.

An ESC calibration should sort out the issue with some motors not starting or you can increase the MOT_SPIN_ARM parameter to account for the size of the deadzone at the bottom of the ESC’s range. You should make sure MOT_SPIN_MIN is also 0.02 above the MOT_SPIN_ARM.

Thanks again for the reports!

Any time!

I am in Stabilize when this happens.
I am accounting for the 2 second delay.
This is seen on multiple rev ups, way after the 2 second arm delay - replicated on demand.
Also, sometimes on the rev-up, the craft is almost to the tipping point before the other two motors kick in.

Wasn’t there an issue with Simonk Firmware and PixHawk?
What I do not understand is the issue is not there with 3.3.3

All of this was discovered when I saw someone else PixHawk based craft land (RTL, Land or auto command) and the motors turned off instantly.

Mine continue to run for almost 5 seconds after RTL, LAND or AUTO land.

Video of the delay issue:

Two motors opposite motors spinning up faster than the other two means it’s trying to control it’s yaw but isn’t able to probably because it’s on the bench.

I think the delay you’re seeing in the throttle is caused by the spool-up logic which takes 0.5 seconds to spool up and another 0.5 seconds to spool-down. It’s possible we could shorten this time.

If you’re feeling a little brave, here’s an experimental AC3.4.2-rc2 firmware with the spool-up time reduced to 0.1 seconds. Maybe you could give it a try to see if it improves things?

Thanks for the feedback!

I’ll put it on my list for this weekend.
Got to have a stable platform for a construction update video I compile on a monthly basis for the school I work for.

This is no reflection to you and your abilities but I am not sure if this experimental version will help.
I have seen this behavior since 3.2.1 with APM2.8. I thought the delay was normal until a friend showed me that PixHawk landing. So I upgraded to get that effect thinking that would be great, props shut down on touchdown to prevent tipover in case of wind kicking up. (lost an ESC to that effect once on APM2.8)

Then, I saw the same behavior on 3.3.3 as 3.2.1
And then I noticed the THROUT delay as in the video.

But I will certainly check for the opposite/ adjoining motor issue fix with your firmware.

(Don’t hijack a topic, start a new one :wink: ) Thx :thumbsup:

2016-11-19 16-01-21.zip (2.1 MB)
3.4.2 is even worse with this issue.
Spooling up has suffered a setback - quite close to 2 second response time from my input to the motors spinning.
And even then, motors 3 and 4 do not spin until I get to about 30% throttle and even then, they are lagging…not catching up.

Too many “new” things going on to compare to 3.3.3 issues.

Logs uploaded as requested

Not a bump - additional information

I just completed a Tarot 680pro HEX build and I just performed the maiden flight with displays the SAME behavior as my 550 HEX and 450 Quad.

Motors will not shut off on touchdown during automated landings.
And, there is still a throttle delay between RCIN and RCOU Ch3

Let’s review;

450 and 550 on 3.3.3 - motors will not shut down on automated landings/ delay between throttle action and motor spin as shown by log file.

450 and 550 on 3.4.1 - same behavior.

450, 550 and 680 on 3.4.2 - same behavior

550 on 3.4.3-rc1 - putting the throttle to 100% and pulling back within a split second, the motors are so delayed they react after the throttle is back to 0%

And this behavior is seen with the release of 3.4.3
Motors will not shut off on touchdown during automated landings.
And, there is still a throttle delay between RCIN and RCOU Ch3
Someone please help.
I cannot get the same behavior as my friends do with their 2.4.8 Pixhawks.

And, this issue has been going on for too long - OP below:

So, the normal, unaltered behaviour of 3.4.x is the one here from this https://youtu.be/ua8OLkIvyas?t=5m08s

where the automated landing deploys the landing gear automatically and stops the motors after landed.

I would suggest that you reset your config and start from scratch. To do that flash a ArduPlane version reboot and then flash again Copter.

The delay you speak on TH is really dependent on which flight mode is active, because most of the modes are like a fly by wire system, where the system receives a order and tries to comply within a given set of parameters with the desired user input.

If you want a more “direct” mode try Acro.

This is a completely wiped firmware load by loading ArduPlane then 3.4.3 from MP.
That has begun to be my common practice to loading firmware.
This happens with the following flight modes:
Stabilize (delay in energized motors stopping from being energized)
PosHold with zero throttle descent.

I see your video and that is exactly what I get.
However, I am now checking with the other group to see if they can link me the video of the shutdown I described.

Shooting from the hip here, but make sure you don’t have any delay programmed into your throttle channel on your TX.

Verified, no delay there.


I installed my CX-20 Tx/ Rx on my DJI550 - same throttle/ LAND delay.
Still waiting on that friend’s video of the instant shutdown on LAND

Update - This is why I got PixHawks for my crafts but I do not see this landing behavior.
Motors shut off instantly on contact (listen to the motors de-energize on contact)
They still spin but they do not have power to them - mine do as seen in the previous video.

And even more evidence of the motors shutting off instantly on landing.

Please…this issue was originally posted in September and is still not resolved.