When the system is up, there will be three device nodes ttyS0, ttyS1, ttyS2 in the /dev directory, and set the tx of ttyS0 Connect to PC via serial port with rx, and execute echo 111> ttyS0 in the
When the system is up, there will be three device nodes ttyS0, ttyS1, ttyS2 in the /dev directory, and set the tx of ttyS0 Connect to PC via serial port with rx, and execute echo 111> ttyS0 in the