Hi Alan
As the developer of the driver you can implement it whatever way you think is best. That is ok.

Backlash code in myfocuserpro2 has evolved over the years from lots of user feedback and lots of tests and trials. Not everyone uses rack and pinion or crayford etc. It became very evident that the ability to support different values in and out and control them (enable/disable) became a big bonus as it is not the same on all systems and not within a hair breath of each other, and depending on the step size value there can become large differences.

There should be no appreciable bias if the backlash was set correctly using the method outlined in the manual. If other methods were used I would say you have a good point. As for the real stepper position becoming invalidated over time that is a whole new subject, and I would be happy to share my thoughts and experiences on that, but I think the amount that backlash causes to that invalidation is rather small in the larger scheme of things. In the best of worlds, there are home limit switches and the focuser is sent to home before use, which helps to reduce the errors in position.

Regards
Robert

Read More...