A stepper motor is driven according to step driving modes including a full-step driving mode, a half-step driving mode and micro-stepping modes. The stepper motor may also be driven in an acceleration phase. A method of controlling the stepper motor includes controlling the current step driving mode of the motor by a processing unit. During the acceleration phase of the stepper motor and the stepper motor being in driven in a current step driving mode other than the full-step driving mode, the processing unit tests, after each speed increase, if a remaining computing power of the processing unit is sufficient for control of the stepper motor to remain in the current step driving mode, and if not the processing unit, in presence of a first switching condition, switches control of the stepper motor to the driving mode having the closest coarser step.