随机生成6为密码并写入密码卡，涉及串口编程-6 randomly generated password for the password and write cards

串口发送开始信号，数码管随机生成十位密码，然后通过按键选择六位密码，按下确认键，将密码发送至上位机(Serial port to send the start signal, the digital tube randomly generated ten password, and then press the button to select the six password, press the Enter key to send the password to the host compu