[A4988] Default microstepping settings


I’ve connected an A4988 driver to a 1.8º NEMA 17 stepper motor as follows:

  • The pinnes STEP and DIR are connected to a Arduino Nano.
  • The MSx are floating.
  • RESET is connected to SLEEP.
  • A 25V 100uf capacitor between VMOT and GND.
  • As power source I’m using a PC power supply (12V).

Everything goes ok, but
I have to do 400 steps to reach 1 revolution, when in theory should be 200 steps. Why?
Can the A4988 be working in half-step if the MSx are floating?
Should I pull down the MSx?

Thanks in advance.
Regards, Mariano.

A brief glance through the A4988 data sheet will reveal that the MSx inputs are internally pulled down, for a default mode of full step.

Do you have a common ground between the MCU and the A4988?

Without additional information, such as the motor current rating, winding resistance, power supply current rating and A4988 current limit setting, or the program you are using, it is impossible to know what, if anything, might be a problem.


If you post your code, I can take a look to see if there is anything obviously wrong.