Check out my solution, posted earlier last year in this thread: 

indilib.org/forum/focusers-filter-wheels....html?start=48#54478

That has been working flawlessly for me ever since. 
 

I see. Today is arrived arduino and stepper 5V is perfect.
Ettore

To share my setup

indilib.org/forum/focusers-filter-wheels...er-driver.html#69334

@Kevin My system is now working. The WaveShare HAT obviously was faulty, the replacement part does work now. Focus in & out in the focuser module does spin the motor in the correct direction, movement is smooth and silent. There might be an opportunity next week to try the autofocus under real time conditions outside. I will report. Two question:1. So far I finished an imaging session leaving the telescope focus where it was at last. When I now start Ekos the next time the actual focuser position is at 0 in the focuser module. If I wanted to check the focus with autofocus, I can only focus out, not focus in as a position below 0 is not possible. What do I do to change the field „Steps“ to a value >> 0 without that the motor spins so that both focus directions are possible? I tried with setting the absolute position to a certain value, but then after finishing the INDI server, the motor spins to bring the former absolute position does to 0. 2. What are the parameters „Polling (Perod(ms), in options tab)“ and „Syn(Steps), in main control)“ used for? Thank you for the support. It seems to be a great driver.

You can use the Syn control to set the driver's notion of its position to an arbitrary value. So if you know that you finish up one session at position 450, and don't touch the focus, next time you fire up your system you can Sync to 450 and go from there.

Those of you who suspect a defective Waveshare HAT might want to try using the Motor B controller.
If I am not mistaken, to select which motor driver is used edit the file wmh_focuser.cpp
Edit line 91

@ Ihoujin

The defect that I found on motor controller A did exist also on controller B, I checked both. The faulty board had a board revision 2.1, the new board did not show a revision at all, so I suspect a design change or a faulty production lot ...

@ Kevin,

I was out in the garden this night and tried the waveshare focuser: it worked like a charm! Great stuff!

Excellent, glad to hear it!
 

I thought I should share what I have done. So here is one of the focusers I have created based on the Waveshare Stepper HAT.

Very nice!  What stepper did you use?  I ended up using a larger stepper (NEMA-17) with a belt/loop under tension.  I really like the smaller stepper and worm gear arrangement you used.  And for this purpose, a larger gear ratio seems better since it enables finer control and decreases the required torque to move the focuser.

It's a tiny stepper motor I found on Aliexpress with a built in 50:1 gear box. The worm ratio is 120:1. Together it is a very high gear reduction. The position resolution is insane. A command for 100 steps barely has a noticeable effect on a bahtinov pattern. I had to use an initial step size of around 800 for the autofocus to get a good V curve.

I am thinking of selling my design as a kit.