What kind of serial port? How is it connected? Are the grounds hooked up?
A typical DB9-style PC serial port operates at around 12 volts, that's way more than what your Arduino can handle... Voltage level shifting is required to make it work.
What kind of serial port? How is it connected? Are the grounds hooked up?
A typical DB9-style PC serial port operates at around 12 volts, that's way more than what your Arduino can handle... Voltage level shifting is required to make it work.