数字万用表的简单功能，可以测试一些电压，一些简单是程序在里面-Changes in light water

采用C51单片机实现高精度的数字万用表程序，可以精确到小数点后两位！-Adjust the output PWM duty cycle procedures, key control PWM frequency and pulse width, press S2 to change the frequency, press S1 can change the width, in turn, will not be able, S1 is defined as P3.3, S2 defined t