A programmable filter with adjustable cut-off frequency is designed based on AT89S52 microcontroller unit(MCU) and X9241M digital potentiometer
and the resistance of X9241M can be selected by software program.Experimental results show that the cut-off frequency error is less than 10% when stepping from 6 kHz to 20 kHz.The programmable filter can be applied to the signal filter processing of data acquisition systems.