set current

[ziyangwang007]

Thanks for your work on TMC2130 library.

I feel confused about setting current.

I find two methods to set current.

One method is to write the "irun“ and ”vsense “ register. and then the "Irms" could be calculated by: (float)(irun()+1)/32.0 (vsense()?0.180:0.325)/(Rsense+0.02) / 1.41421 1000;

The other method is for SilentStepStick2130 by measuring the voltage on the Vref pin and adjusting the voltage with the potentiometer. I achieve it follow by the instruction in other website: https://learn.watterott.com/silentstepstick/faq/ https://wiki.fysetc.com/TMC2130/

The question is that what is the connection between these two methods, and the meaning of the mathematical expression in your library.

Thank you!

[teemuatlut]

irun and ihold set the registers directly and you'll need to calculate the CS values yourself, also accounting for selecting the correct vsense setting.

SilentStepStick2130 is a shorthand for setting the current with default hold multiplier and default Rsense value from Watterott TMC2130 design. This can also be achieved by just calling rms_current(mA). It does not measure the voltage on Vref. https://github.com/teemuatlut/TMC2130Stepper/blob/188d5fe35d4406a8e342737dc0107046d1ce1585/src/TMC2130Stepper.h#L17

You can see the logic behind the math in here: https://github.com/teemuatlut/TMC2130Stepper/blob/188d5fe35d4406a8e342737dc0107046d1ce1585/src/source/TMC2130Stepper.cpp#L343-L371

The easiest way to set the current is just with rms_current(mA) or setCurrent(mA).

[ziyangwang007]

Thanks for your reply!

Yes, for software part, I could set current by these functions: setCurrent() or SilentStepStick2130() or run_current() or irun().

But after I completed the software part to set current, I could still change the current by changing hardware part. I could change the resistance of a resistor on the SilentStepStick2130 board (Vref could be changed).

So it makes me confused.

irun and ihold set the registers directly and you'll need to calculate the CS values yourself, also accounting for selecting the correct vsense setting.

SilentStepStick2130 is a shorthand for setting the current with default hold multiplier and default Rsense value from Watterott TMC2130 design. This can also be achieved by just calling rms_current(mA). It does not measure the voltage on Vref. https://github.com/teemuatlut/TMC2130Stepper/blob/188d5fe35d4406a8e342737dc0107046d1ce1585/src/TMC2130Stepper.h#L17

You can see the logic behind the math in here: https://github.com/teemuatlut/TMC2130Stepper/blob/188d5fe35d4406a8e342737dc0107046d1ce1585/src/source/TMC2130Stepper.cpp#L343-L371

The easiest way to set the current is just with rms_current(mA) or setCurrent(mA).

[teemuatlut]

If you've enabled I_scale_analog, then the current is also scaled according to Vref.