FT232RL USB 3.3V 5.5V to TTL Serial Adapter Module
 
The FT232R is a USB to serial UART interface
A low-cost way to add USB capability to microcontrollers. Use this to give your own breadboard a USB capability for bootloading or downloading sketches.
RXD/TXD transceiver communication indicator
Includes over-current protection, using a 500ma self-restoring fuse
This board includes a DTR pin needed to auto-reset when downloading to your device.
USB Power Supply: 3.3V or 5V