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INDI Library v1.8.5 Released (19 Apr 2020)

April 2020 release of INDI Library v1.8.5 introduces new drivers while providing fixes and improvements to existing devices and core framework.

Always focus from one direction

1 month 2 weeks ago 1 month 2 weeks ago by kross.
kross
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Always focus from one direction #54655
Well actually....

I looked at that picture. 21 iterations to reach focus! Wow. Polynomial works pretty well for me, and usually in 7 or 8 iterations.

I suspect a universal anti-backlash mechanism would be useful, so that it isn't tied to one focus algorithm. Or more likely, it will need to be added to polynomial algorithm. (Are there more algorithms? I don't remember).

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1 month 2 weeks ago
DerPit
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Always focus from one direction #54664
IIRC I had placed a wishlist request for this feature some time ago. As in a general option for all focusers to always end moving inwards, ideally with a configurable overshoot amount. I think it would be a very useful thing to have!
So I would definitely welcome it if you go ahead and implement it :D

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1 month 2 weeks ago
knro
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Always focus from one direction #54667
So you can implement this in your driver with Ekos needing to know about it. Once you detect a switch in direction, you perform the large move and then go back to that position again. As far as Ekos is concerned, it's just waiting for you to finish your move.

Jasem Mutlaq
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1 month 2 weeks ago
DerPit
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Always focus from one direction #54669
But couldn't (shouldn't?) that capability go to the general INDI focuser class, so that any driver can benefit?

openSUSE Tumbleweed KStars git INDI git
GPDX+EQMOD, CEM60EC, ASI1600+EFW+EAF+ASI290 mini

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1 month 2 weeks ago
El Corazon
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Always focus from one direction #54671

DerPit wrote: IIRC I had placed a wishlist request for this feature some time ago. As in a general option for all focusers to always end moving inwards, ideally with a configurable overshoot amount. I think it would be a very useful thing to have!
So I would definitely welcome it if you go ahead and implement it :D


I also would love to have that configurable overshoot amount, both on the initial way out (how far from established focus the module moves the focuser before homing in again) and on the return after the U-curve has been established.

In theory, the polynomial algorithm should be faster, but that only applies to a system without backlash or with only minimal amounts. The moment there is any backlash, the linear approach is clearly superior in my hands.

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1 month 2 weeks ago
El Corazon
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Always focus from one direction #54672

kross wrote: Well actually....

I looked at that picture. 21 iterations to reach focus! Wow. Polynomial works pretty well for me, and usually in 7 or 8 iterations.

I suspect a universal anti-backlash mechanism would be useful, so that it isn't tied to one focus algorithm. Or more likely, it will need to be added to polynomial algorithm. (Are there more algorithms? I don't remember).


The approach to the minimum is very methodical and does take longer than the polynomial, but it is also very versatile, as it works GREAT with analog focusers and FCUSB. There, the movements of the focuser are highly load dependent, in contrast to steppers. Nonetheless, the linear focuser handles that with flying colors. But making it more configurable, as Peter suggests below, would definitely be especially useful for such analog systems, I agree.

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1 month 2 weeks ago
kross
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Always focus from one direction #54705

knro wrote: So you can implement this in your driver with Ekos needing to know about it. Once you detect a switch in direction, you perform the large move and then go back to that position again. As far as Ekos is concerned, it's just waiting for you to finish your move.


I've already done that. I was asking if putting this in Ekos as a universal solution was better. :)

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1 month 2 weeks ago
kross
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Always focus from one direction #54706

DerPit wrote: But couldn't (shouldn't?) that capability go to the general INDI focuser class, so that <em>any</em> driver can benefit?


Doing it there, rather than in the Ekos UI, is also an option. I hadn't considered that.

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1 month 2 weeks ago
ChrisRowland
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Always focus from one direction #54740
A number of focuser drivers already have backlash implemented. it isn't difficult.

Implementing it in the base class could be quite a lot more work because it would still need to refer to the actual driver to handle detecting when the initial slew has stopped, start the final slew and wait for it to stop. All of that is currently done in the driver at present.

There's also a lot of variability in how backlaash is done. I've described one that is handled in the Indi driver but it could also be in the low level driver hardware.

Better to let each driver handle it in the way that suits it.

If you need an example the Celestron SCT focuser driver has one implementation.

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1 month 2 weeks ago
knro
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Always focus from one direction #54741
I concur with Chris. This has a very good potential of introducing regressions if introduced at the base class. Let each driver handle it as it sees fit.

Jasem Mutlaq
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1 month 2 weeks ago
kross
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Always focus from one direction #54743
Very well. That certainly makes it easier for me, since I've already done most of the work in my Waveshare driver. :)

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1 month 2 weeks ago
RDBeck
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Always focus from one direction #54810
I implemented backlash compensation in my moonlite-compatible arduino code at https://github.com/beckrd/Moonlite_Focuser . I always move x steps beyond the targeted amount when moving outward and then move to the target inwards. As Jasem mentioned, the focus module just waits for the moonlite driver to report that the focuser is at target position.

Feel free to use the code or logic as you see fit for your implementation.

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