Recently I purchased a beagle board RevC4 and the cables along with
it. The null modem serial cable supplied is of 9-pin but on the board
there are 10 pins for serial. How to connect that cable to the board?
Do I need to cut the pin on the board or solder the required wires and
connect to the null modem cable.
You need to use an IDC10 to DBM9 cable (also called an AT/Everex
cable) for the serial connection. Please see
http://elinux.org/BeagleBoardBeginners#Serial_connection and
http://elinux.org/BeagleBoard#RS232 for more details.
The cable can be ordered from Digikey, soldered manually or found in
computer hardware stores that provide hardware service (it's used to
bring out the serial port from some older motherboards to the
chassis).
Yaman
hi there will 10 pin on the beagle board buy ribbon cable that is
10pin-9pin connector.
I made one myself
connect the 2,3 and 5 pin of the header to 3,2 and 5 pin of DB9 connector
it works for me hope it works for your too 
regards
Nicobari