嵌入式串口实例，有部分测试程序，功能：每隔2秒发送“1234567890”，并打印内容。接受也是每2秒一次，并打印内容，出错时打印出错信息-example, some of the test procedures, functions : every two seconds to send "1234567890", and print content. Each also received a two seconds, and Print, Print error error message