cyclegadget:
ah... another question, is it possible to directly connect my arduino uno r3 board TX and RX and gnd pin to RS232 serial port pin 2,3 and 5?
You need a max232 chip for that.
A link for example: http://sodoityourself.com/max232-serial-level-converter/
so i cant directly wire up those of pins of TX, RX and GND? and why?