Interfacing the RabbitCore RCM3200 with 5V

Hi all,

I would like to interface the RabbitCore RCM3200 to a 5V system for serial communication.As I understand my options are 2:

a) Since the Rabbit Core Module (operates at 3.3V logic levels) has 5V tolerand pins, I could just use it with the 5V system (which is a 5V TTL device with a minimum high-input voltage of 2.1V).
I would also probably need to use some series resistance to reduce the current (for the case of 5V input in the 3.3V Rabbit Core).

b) Use an RS232 to TTL Shifter and interface with the RS-232 transceiver of the Prototyping Board.

I have little experience with hardware interfacing and I could use any advice or comment

Thx

What is your 5V device? look 74hc245 bi-directional buffer