THE Bipolar Stepper Driver. Have you seen it?

[Jonathan]

Whilst I agree that the higher resolution microstepping being available with the newer IC is not much especially useful, that statement is largely irrelevant - the lower Rds alone is the reason to use the A3979, especially when you're trying to make this compact. Lower Rds means lower heat dissipation, which means less space is needed to extract the heat, i.e. the heatsink is smaller.

Unless you have 2tpi and want .0001 then it is very usefull...now I'm curious what microstep are all of you using on your machines right now?

Not really, as if you really need extra resolution you'd change the drive ratio between the screw and the motor as the accuracy of micro-stepping is limited. A lot of people here use 10mm pitch screws driven 1:1, so that's effectively 2.54tpi...but the main factors in choosing the microstepping valua are the maximum frequency your controller can output, the maximum feedrate you require and the value which causes the least resonance in the machine.

[John S]

Every time you microstep you loose torque.
So by the time you drop down to 1/16th and need to overcome stiction it will miss steps unit it has enough to make a sudden move so basically anything over 8 is a waste of time.

Also remember systems can't remember microsteps so a shut down and start up will go to the nearest full step regardless of where it was.