Introduction - If you have any usage issues, please Google them yourself
//Experimental board AVR procedures, uart applications, and computer communications, PC loopback send data// connection definition: PD0-RXD PD1-TXD switch location: SW6-7/8 open.// Use the serial port debugger, use the hexadecimal mode, let PC send a character to the MCU, and then will receive the MCU to return value.// Note: This program seeks to UART understanding and demonstration of procedures suitable for beginners to use.// Use the chip 8MHz crystal, 9600bps baud rate