> Would you need designated hardware, or could it be done all
> electronically via given wires (Stepper or bldc servo)?

A driver like the L298 has low-side sense resistor in series with
the motor coil. The voltage across the resistor is passed back to
eg an L297, which is commonly used with the L298. The L297's
comparator uses the coil voltage vs a Vref to determine the coil
current, for chopping etc. Vsense is available to any IC

http://www.uni-kl.de/elektronik-lager/419182

As Jason shows, a discrete circuit can be used to deliver Vsense
to an ADC

I'm not sure what you mean by "Resistance" in the Subject. Do
you mean the amount of current needed as the motor tries to
move against a load ? If the coil is being chopped or PWMed,
then the start of a drive cycle can be used as the start point for
gathering data to track the increasing coil current

Joe


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