Is it possible to adjust current to a stepper motor with code using Arduino and a stepper motor driver?
I need to keep the voltage more or less the same to match the stepper voltage but then bring gown the current so I can adjust the torque.
This has to be done with code, not with a screwdriver or anything physical.
Is this possible, or is there another way to adjust the torque up and down with code?
No.
Sort of but it gets messy and there is not enough detail in your Q. to give much real advice.
Voltage can play a part in speed/torque calculations but the better option is normally speed as that certainly affects torque with almost all steppers.
Usually more speed = less torque
Otherwise the short answer is the same as zwieblum says.
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I think that this is an XY question. Why do you want to be able to control the torque.