Hi,

I am testing the serial ports on a Single Board Computer(SBC) running Linux kernel 2.6.29. I usually do this by connecting the serial port to another PC serial port, then doing "cat /dev/ttyS0" on PC and "echo hello > /dev/ttyS0" on the SBC. However in the current system, "echo hello > /dev/ttyS0" command does not return at all! Also no characters appear on the destination port. I am running the echo command as root. The system boot messages show that the serial port in indeed /dev/ttyS0. What could be the problem?

Thanks in advance,
rohit.

Could be a plenty of different problem...
Is the proper serial driver loaded into the running kernel (cat /proc/devices)?
Is the serial hardware properly configured (setserial)?
Is the serial communication properly configured (stty)?

Does it return if you disconnect the device from the serial.