RC filtering, triode amplification and Schmidt shaping are adopted. According to the relevant data of the speed sensor, the pulse signal of the speed sensor is adjusted by RC filtering, triode amplification and Schmidt shaping. Because the working environment of most cars is bad, it will interfere with the speed sensor signal, so it is necessary to process the speed pulse signal before inputting it to the interrupt port EINT0. Here, RC filtering, triode amplification and Schmidt shaping are used to adjust the speed pulse signal.