@Jerry21 Translated to English:

Good afternoon, I need quick help.

I have built a seed meter for sowing field crops with a Uno and an Arduino Stepper Motor Shield v2. I created a test unit a couple of months ago that worked well. With the help of the example stepper code, I was able to vary the speed, etc., from 1 rpm to very quickly.

Yesterday I reassembled it to place it on the machine, and now I have noticed that the stepper motor no longer has consistency, and I have returned for example code.

If I vary:

myMotor->setSpeed(10); // 10 rpm

4 rpm are slower than 1 rpm, 8 rpm are faster than 10! and the variations are continued at higher speeds.

I tried a brand new second engine shield v2. I have tried another stepper motor.

These are the motors I use: [link deleted]
12-volt power from a very large battery.

I can't explain it at all, but it's business-critical.

I just connected version 1 of the motor shield board and that's fine!

Sorry, we cannot support you here, this forum is for users of Duet electronics running RepRapFirmware. Try asking on the Arduino forums.

Ian