1.This module requires a 3.3 volt supply for VCC, and 3.3V logic.

2.It is not 5V tolant,Connect RX or TX on 5V will destroy this module.

3.You must use a logic level converter, or a 3.3V for Arduino.

4.The 3.3V supply on the Uno has inadequate current capabilit to power this module.

5.You must provide a separate,higher 3.3V supply(about 300mA or better).