Returns the number of μS between your call to read() and when the last tick was received.
It can be used with a low resolution encoder in conjunction with getDurationOfLastTick() to estimate the fraction of a tick.
Where Encoder is the name you have given to the device in Project Designer.
This function only returns sensible values if the encoder is using interpolation.
If the encoder has not been rotating for a long time then it may return a strange value. You can guard against this by checking the motor is currently being asked to move or whether it is at a stand still.