Using the digital current control version of the MP6500, I want to switch the stepper current between 1.5A (operational) and 0.5A (standby). So I have left pin i1 open-circuit and am switching pin i2 between ground and +5V from a digital pin on the arduino as required. But when in low-current mode (pin i2 HIGH) the stepper vibrates noisily rather than just sitting there as expected (no stepping in this mode).
So is pulling pin i2 to +5v the same as leaving it open-circuit (high-Z as on the data sheet)? If not, is there a recommended way of driving i2 from an arduino to get the desired effect?
If the two modes of operation are equivalent, does anybody have any thoughts as to why I am getting this strange behaviour?