用AVR单片机AT8535的普通IO口来模拟串口RS232的发送和接受-With AVR AT8535 common IO port to simulate the sending and receiving RS232 serial port

但我们可使用的串口资源有限的情况下，我们可以利用单片机的IO模拟串口发送数据。-However, we can use the serial port with limited resources, we can use the single-chip analog serial IO to send data.

verilog IO模拟串口,用IO模拟uart进行串口通讯，无需硬件串口(Verilog io analog serial port, using io simulation UART serial communication, no hardware serial port)