I need help in configuring the serial ports correctly. I have used sample codes from How-To pages with limited successes. One of the problem is that after I write to /dev/ttyS1, the permission changes from crw_rw_rw_ to c_w__w__w_. This does not occur to other ports. Another is that the write() reports the bytes written, but the target device did not receive the bytes. However, I am able to read data from the target device. Can someone explain the minimum configuration need to perform asynchronous I/O to multiple ports? Since the read() can only read 255 bytes at a time, I would also need to know how to activate interrupts for multiple ports. Thanks in advance.