LCD Encoder Have Slow Response When Connected with Arduino Uno and Stepper Motor

Projects General Guidance
9

I'm not sure whether is there any blocking in coding or not.

u8g.firstPage();  
  do { draw(); } while( u8g.nextPage() );
}

Unfortunately, the display code is blocking. I don't know how the execution time compares to the desired 10ms between stepper pulses, but it may be longer.

You may wish to update the screen, only when the values for the digitalRead(pinEncButt) or encoderValue have changed.

I'm not familiar with your display or the library, but it may be possible draw unchanging portions of the display
(for example "Test Encoder" and "www.mauroalfieri.it") in set up, or otherwise only one.