mkr1000 and SIM800L

Hello to everybody,
i have buy a gsm module

and try to study how connect this module to the mkr1000, but i'm not sure (and if) is necessary protect TX and RX pin

GSM -> mkr1000

VCC -> diode 1N4007 -> 5V
RXD -> (directly or with resistor?) pin 14
TXD -> (directly or with resistor?) pin 13

Thanks in advace for the help.