功能：开机检验数码管好坏，用串口通讯发送一个十六进制数，两位数码管显示，并有八个发光二极管 以二进制的形式点亮，其十六进值与数码管显示一致。-Function: boot test digital tube mixed with serial communication by sending a hexadecimal number, the two digital tube display, and eight light-em