Replacing analog potentiometer with digipot for DC motor speed control
Since the datasheet mentions an isolated signal, you could use an optocoupler from an arduino PWM output:

The cap smooths the PWM into a more &quot;DC&quot; voltage.
&quot;+5&quot; &quot;out&quot; and &quot;gnd&quot; on the right side of the circuit should be the three terminals of the existing pot.