Sparkfun Logic Level Convertor:
3.3V 5.0V
LV HV
-> TXI TXO ->
<- RXO RXI <-
--------chan1---------
LV HV
GND GND
--------chan2---------
<- RXO RXI <-
-> TXI TXO ->
to use for 3.3v to 5v serial
-> TXI TXO ->
<- RXO RXI <-
--------chan1---------
3.3v --------- LV HV ------- 5v
3.3v gnd ----- GND GND ------ 5v gnd
--------chan2---------
3.3v Rx ---<- RXO RXI <---- 5v Tx
3.3v Tx ----> TXI TXO ->--- 5v Rx
Got this from Sparkfun
Check these out for I2C usage:
http://trandi.wordpress.com/2011/01/03/razor-9dof-imu-i2c-to-arduino/
http://electronics.trev.id.au/2011/06/19/digital-compass-using-i2c-arduino-and-sparkfun-compass-module/>
