batata004:
So, in 200 steps (one revolution) this motor should take 0.2 second but no, it takes almost a second.
I suspect you are trying to get the motor to move too fast without any acceleration. It is probably missing steps that you are not aware of.
Start with a slow speed and gradually increase the speed to see what is possible. For high speeds you will need to ramp-up the speed so as not to miss steps (and ramp-down when stopping). Stepper motors also suffer from resonance - especially if they have no load.
These links may be useful
Simple Stepper Code.
Stepper Motor Basics
saximus:
The A4988 library recommends no more than 200RPM.
??? What A4988 library?
An A4988 driver has no limit like that. It requires at least a 1µsec HIGH and 1µsec LOW pulse which implies a max of about 500,000 pulses per second.
...R