@guitobenito, your topic has been moved to a more suitable location on the forum as you're not interfacing with a PC 
RS232 uses different signal levels and they are inverted. You will need a converter, e.g. based on MAX232. Search for Arduino TTL to RS232 or for Arduino RS232. You will need the sigal pins 1, 2 and 3 of your image.
For RS485, you will also need a converter; search for Arduino TTL to RS485 or Arduino RS485.
Both should be equally easy from a hardware pespective; RS485 will be a little more complex from a software perspective.
Note: just picked two boards from the SparkFun website; there are others.