An optimized control scheme for driving a stepper motor with the index control mode is proposed and analyzed in this paper to control the stepper motor more accurately and effectively. Based on the built-in five-digit digital-to-analog signal converter (DAC), six stepper motor operating modes, namely 1/32 micro steps, 1/16 micro steps, 1/8 micro steps, 1/4 step, 1/2 step, and full step, can be selected. Only four control ports are required for switching of operating mode and motor steering. The simulation results show the optimized circuit can output accurate current signals to control the stepper motor.