Feature request: Instant trim ?

Hi guys,

I'm using Deviation with my Devo8S (in fact, I bought it because of DeviationTX to replace my Spektrum DX5e and control my DSM2 planes), and I love it. Thanks for this great work !

I had a look at er9x and Open9x, and they provide a very cool feature called "Instant trim".

Instant Trim to trim your model instantly from the stick positions.
Note: Trims are not transferred for Thr stick.

The use case is very classical for a plane: first flight(s) always need to do have trimming on most axis. With this feature, you just keep the flight on a straight line by correcting on the sticks, toggle the switch and the trims on Ail, Rud and Ele are setup automatically.
You just need to release the stick to their neutral and your plane is trimmed and flight straight !
So very useful.

Do you think it could be a new feature or is it possible to program this function with some complex mixer mojo ?

This looks like a great feature and it shouldn't be too hard to implement.

I think this is just a new switch type, which read ELE, RUD and AIL channels values when toggle from Off to On and write it to the ELE, RUD and AIL trims when toggle from On to Off.

Should it be implemented as a special mode with a switch only temporarily associated to it? The switch (or maybe a button?) could have its normal function after trimming.

Hi,
I think that we have just to read all INPUTS that are assigned to TRIMs (Menu Model => Trims) ... and then apply the INPUTS values to
the corresponding trims ... Is it false?

domcars0 wrote: Hi,
I think that we have just to read all INPUTS that are assigned to TRIMs (Menu Model => Trims) ... and then apply the INPUTS values to
the corresponding trims ... Is it false?

I think domcars is correct, you want to transfer the value of the Sticks at that moment to the Trims.

As for disruption in flight - for a plane that is not to serious as one would press the button once in stable flight and it would be simple to release the sticks to neutral the moment you press the button.

I am stil trying to think how it can be used to set the SUB-TRIMs on FBL heli's in flight where you have drift due to a swashplate that is not 100% level?

Take care RandMental , this is not to set SUB-TRIMS but TRIMS!
Anyway this is not userfull for helis (this feature must probably be disable for heli models) but as said by BitOne for planes.

I think that a good start can be a call to TRIM_Instant() in the main.c EventLoop() function

Understood! I know we are talking about TRIMS, not SUB-TRIMS, which I agree for Heli's should be disabled.

My comment about SUB-TRIMS was because after getting a new Heli in the air or after repairs, I normally land a few times to change a SUB_TRIM value a few clicks up or down to get the swashplate "level" and remove a bit of drift (450 size and larger heli's)

I never use SUB-TRIMS to level the swashplate, I use ball links.
I think that SUB-TRIMS are made to precisely adjust the servo arm on neutral.
Sorry for my frenglish but when I said that the feature has to be disable for helis, I did'nt spoke about TRIMS or SUBTRIMS but about the InstantTRIM.

I use this feature all the time in er9x. I assign it to the trainer switch (as most er9x users do).

And yes, it DOES apply instantly, not after landing. It works great. You hold your sticks so the plane is level, pop the trainer switch and then a moment later let go of the sticks. It takes a little timing but great function.

After you land, you can see what the trims are at, and either just leave them or make the proper changes in your links.

domcars0 wrote: I never use SUB-TRIMS to level the swashplate, I use ball links.
I think that SUB-TRIMS are made to precisely adjust the servo arm on neutral.
Sorry for my frenglish but when I said that the feature has to be disable for helis, I did'nt spoke about TRIMS or SUBTRIMS but about the InstantTRIM.

No need to apologise, I am sure we all understood what you meant.
I do find many times that a full turn on a ball link is to much, and then subtrim is an easy way to get it adjusted. Especially in the field it helps as you don`t have to fiddle with the mechanics of the heli.

Apologies for going way off topic here.

Hi guys,

Thank you very much for all this valuable feedback.

I really like the operating described by domcars0:

I think this is just a new switch type, which read ELE, RUD and AIL channels values when toggle from Off to On and write it to the ELE, RUD and AIL trims when toggle from On to Off.

Doing this you'll have the choice to apply the trim values while flying or after landing if you prefer.

And if you apply it to a momentary switch, it could work like on ER9X with the trainer switch on the 9X (I do not know if a Devo model has a momentary switch, but I saw a hack to add one on Devo8S).

Now, some remarks on this feature:

Sound Feedback:
Could be interesting to get sound feedback when the stored value is applied to the trim (switch go back to 0 position). It makes sense to me as (if I understand correctly) the future version of Deviation will feature sound feedback on the trim to know if the trim has been applied or not (case where you are already at the limit)
The sound could be two short beeps for example.

Behavior when trims are already applied
Two possibilities:
- only the sticks position is applied without the already applied trim values. It has for effect to forget the already applied value. Not so good as the final trim will not match the trimmed flight if trims were not null.
- the stick values are added to the actual trim values. Much better, as the Instant trim feature work as expected from the user point of view.

Behavior when the stick values are out of the limit of the trims
This case can easily happen when the trim steps are pretty low and the sticks go out of the limits easily. Or it can happen as well when the stick values are plain far from the neutral position.
Two main possibilities (maybe more...):
- trim steps are changed if needed to allow the trim value to match stick positions
- if the value is over the limit, the trim is set to its limit
I would prefer the second solution, as the first one can be very dangerous if using in flight. Moreover, instant trim is about automating trimming. Therefore it should not have a bigger impact area than trim themselves where they are manually set.

But it could be nice to have a way to warn the pilot that the trims have not been fully applied because of over limit value. For example, the same sound than the one produced when manually reaching trim limit could be self-explanatory.

What you guys do you think ?

• On which setup page do you think we can ask the user which switch to use as the instant Trim?
• If a switch is use as the instant Trim it can't be use for anything else.
  If a switch is already assigned for something (mixer for example), we can't propose it for instant trim switch.
• Instant trim is only available for plane models (not for heli).
• For sure new values of trims are : trim old value + stick value (anything else is crazy)

domcars0 wrote:

• On which setup page do you think we can ask the user which switch to use as the instant Trim?

I think on the trim page, it makes more sense (it's a trim feature).

domcars0 wrote:

• If a switch is use as the instant Trim it can't be use for anything else.
  If a switch is already assigned for something (mixer for example), we can't propose it for instant trim switch.

I agree.

domcars0 wrote:

• Instant trim is only available for plane models (not for heli).

No real opinion on that, do not know enough about helis.

domcars0 wrote:

• For sure new values of trims are : trim old value + stick value (anything else is crazy)

You're right !

BitOne wrote:

domcars0 wrote:

• Instant trim is only available for plane models (not for heli).

No real opinion on that, do not know enough about helis.

I try not to use trims with my helis whenever it works. But sometimes I wish I had not to fumble at these little trims (and leave the sticks alone). I think I would use such a feature for my heli for proper setting it up. I would correct the trims effect by correcting the mechanics, of course... And (as RandMental wrote) on the field trims are easier to use than to screw at the mechanics and I would appreciate a fast way to apply them.
But I see that a plane has greater advantage of such a feature.
In another thread we discussed individual trims for different flight modes. Maybe this feature would be a first step in this direction to get a feeling if these flight modes are wanted.

Just a reminder again, for heli's we need to talk about SUB-TRIM (for FBL heli's), NOT the normal trims discussed here for planes.

For heli's I would love a way to translate stick position that results in a stable hover and no drift, into the correct subtrim values as we now discuss for planes. However, I have no idea how to make the back translation, as it will also counter gyro drift (which change over time) in addition to mechanical setup and balance factors.

I'll move this to another thread, it is off topic here.