Backlash compensation in INdI...

[BillyBoy]

Hello all,
I have a question and wonder if anyone can help..or at least explain
I have been using the Pegasus UPB V2 INdI driver with my Pegasus motor..
But I have noticed when I set backlash compensation in the driver to 100 steps, it only works in one direction....which is when moving out, but does not work when moving inwards, also when it is moving out, it applies the compensation on every outward move....
Is this all correct....

Bill

[Evans]

It is correct. Bakclash compensation should happen only in one direction. This is how the algorithm works.
If you try software backlash compensation at NINA or SGPro you will see that they do exactly the same.
Backlash compensation is implemented IN or OUT (never in both directions)

[BillyBoy]

Ok..thanks for the reply...
And should it happen on every focus motor move in that given direction, or just the first time...as I would have thought after the slack is taken up, there is no need for it again, but then when you change direction, that is when you need it, but this does not happen....if I change direction from outward to inward, there is no compensation, yet there is slack there...
I’m confused by this totally....

[Evans]

It should happen for every inwards movement.
This is a nice video explaining the backlash compensation algorithm

https://www.youtube.com/watch?v=K6zge9b18Ew

[BillyBoy]

Yes good video,
But mine is only working on every outward movement, and you say it should be in every inward movement...hence my confusion...
Every time the focuser moves outward, it then moves back in by 50 steps, which is the BC, but when I move the focuser inward, there is no extra BC movement...
Sorry if I am being an idiot...

[BillyBoy]

This is another error I get during a session with the UPB in INdI too....doesn’t seem an issue but wondering what the issue is at it happens all the time...

CFEB975D-C2EC-42E1-9E5B-F29DF500DA74.jpeg (41.16 KiB) Viewed 18760 times

[BillyBoy]

Also how come the backlash steps aren’t taken Into account on the step count, won’t this throw the final figures out, and mean that a repeatable postion is not possible just going by the step number..?. As every time I move out by say, 500 steps out, it then moves back by 50, but still shows that it’s moved by 500 when actually it’s only moved out by 450....
This is all really co fusing me TBH...I have no idea how or even if this thing works properly...please help...

[BillyBoy]

Any help or ideas....?.?

[BillyBoy]

Well, I thought this was the place to get help direct from the horses mouth, so to speak....but maybe not...

[Evans]

Unortunatelly we are not aware how the indilib driver works. Please note that we do not maintain /develop the INDI driver.
Any indi driver issue or question should be posted to the indilib forum. https://indilib.org/forum

[BillyBoy]

I have asked them, and they say the issue is with the Pegasus software as in the INdI driver all that is done is the value of the BC sent to the Pegasus software, this has been looked into at the code level...and it acts the same in other software too....including your own...have you read all my posts...?
As it does not seem so....
All I am asking is for some help....in explaining why it’s acting in this way...as it makes no sense at all....

[BillyBoy]

Unortunatelly we are not aware how the indilib driver works. Please note that we do not maintain /develop the INDI driver.
Any indi driver issue or question should be posted to the indilib forum. https://indilib.org/forum

So why do you state on your website that it’s “fully” compatible with INdI, when it clearly is not....??

[BillyBoy]

As asked already what are these errors, maybe I get a response this time....

DB01EC4E-8642-4EB2-ACC6-A735E9A318B6.jpeg (41.16 KiB) Viewed 18710 times

[Evans]

This is how our backlash compensaion works:

Lets say backlash is 20 steps.
To compensate backlash on telescope focusers overshoots by 20 steps, and then moves back by 20 steps.  Let’s say I want to move by 100 steps as in the previous example.  Then the focuser should move by 120 steps and then move back by 20, and indicate the position at +100 steps, accordingly. 
Compensation should be applied IN OR OUR. (never in both directions). So algorithm applies the backlash in one direction only

[BillyBoy]

So, let me see if I have this correct, if I set an outward move of 500 steps, and my backlash is set on 75 steps, the focuser will actually move 575 steps outward and then 75 inward...?? Hence why the step count has only changed by the original 500 steps...?? Well that makes sense now, if it adds the backlash onto the actual outward move, that was something I did not know....

So have I got that correct...?

If so how come it will only work on the outward movement, in INdI yet in your own software you have the choice of in or out...??
Thanks