1：读取输入P1.0口的电压值，由于硬件实现了将5V以上的电压转换为三分之一的输入定呀，

　　　　 由于电动车单个蓄电池最高电压为12v，经过运放电路，输入到P1.0口的电压值最高是4V

　　　　 2：当读取到的电压小于3V，声光报警电路接通并报警。

　　　　 3：P1.3口具有高低捕获功能，本程序设定是下降沿触发。

　　　　 将捕获到的数字经过转换后送到数码管显示。

　　　　 4：数码管是4位带小数点共阳数码管。用于显示转速大小。转速单位是Km/h。

　　　　 一般电动车最高时速不超过100Km/h，所以数码管前两位显示整数部分，

　　　　　　 后两位显示小数部分。

　　 5: 加入了按键切换里程与速度功能。定义P1.1口为按键功能-1: P1.0 port read input voltage value, due to the hardware implementation of the above 5V input voltage into a third set Yeah, because a single battery electric vehicle for the maximum voltage 12v, through the op-amp circuit, the input to the P1.0 mouth highest voltage value is 4V 2: When reading the voltage is less than 3V, sound and light alarm circuit is turned on and the police. 3: P1.3 port has a low capture feature, the program is set to trigger on the falling edge. The captured after the conversion to digital LED display. 4: Digital tube with a decimal point is four common anode digital. Size used to display speed. Speed ​ ​ unit is Km/h. General electric car a top speed of no more than 100Km/h, so the first two digital tube display the integer part, fractional part of the two displays. 5: adding buttons to switch mileage and speed capabilities. P1.1 port is defined function keys