Hi everyone, we are building a equipment powered by batteries. It has RS232 interface. When we plug/unplug rs232 cable (connecting to PC on another end) with the equipment on, the MCU inside the equipment sometimes crashed. I observed the 5V power line inside the equipment, high voltage spike can be caputred by the scope. I think it is caused by the different ground between the equipment and the PC. Any idea to prevent such kind failure? The rs232 transceiver inside the equipment has ESD protection function. Thanks for any suggestion.