I have attached a PDF that explains what the steppers need in current. The R2 stepper (17HS4402) rating is 1.3 amps. The Robo board uses an A4988 driver with a 0.1 ohm sense resistor. The Robo R2 board Imax current equals the reference, 0.9v, divided by (8 x 0.1 sense resistor) yielding 1.125 amps Imax. From the PDF I can see that microstepping requires 1.414 x 1.3 amp rating of the motor yielding 1.84 amps Imax. There are two windings so I think that number should be cut in half to 0.92 amps. This is less than the 1.125 amps the stepper is being driven with. 1.84 amps would burn up the stepper. Is there anyone more facile with steppers that can help me resolve the current. I am using the Partsbuilt system board an can set the Imax current up to 1.5 amps Imax with an A4988 plug in driver. I thought that I had read that for microstepping the current must be exactly right for accuracy, but I can not find that article right now. Does anyone have any info on over/under driving the steppers in microstepping mode?