Help Arduino Connection

hi i'm using this arduino and i want to interface it in my GSM module SIM900D and test some AT-Commands in Hyperterminal. i am confuse how to connect the two. do i need to use RS232 to TTL converter? my GSM module have only 1 pin for TX and RX and also the Arduino. how i am gonna interface the RS232 to TTL converter to the GSM and Arduino if this device is required?

tnx :~

Arduino(clone)

SIM900D

Links are better than pictures. Links to all the devices in question are good, too.

MrYu2316: hi i'm using this arduino and i want to interface it in my GSM module SIM900D and test some AT-Commands in Hyperterminal. i am confuse how to connect the two.

You need to know what sort of signaling the GSM unit uses on its serial interface - is it TTL, or RS232? In my limited experience RS232 devices usually seem to terminate in a D-sub housing rather than a bare header, so I think there is a good chance it is a TTL interface. In that case you just need to confirm that the two devices are using the same logic levels, or that they're both compatible with each other's logic levels.