FT232RL USB 3.3V 5.5V to TTL Serial Adapter Module (Cable sold separately)
 
Description of FT232RL USB TO TTL Converter
The FT232RL USB to TTL 3.3V/5V FTDI Serial Adapter Module is a popular module that is used to connect a TTL serial communicating device to a PC via a USB mini port. This converter module has options for different output voltage options which are set by the jumper on the board. FT232RL USB to TTL Serial Adapter Module can be used to upgrade any legacy peripherals to USB.
 
In Summary: 
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
 
Applications of FT232RL USB TO TTL Converter
Below are the applications of FT232RL USB TO TTL Converter:
Programming AVR, ARM-based microcontrollers/microprocessors.
USB to RS232/RS422/RS485 Converters
USB Smart Card Readers
For serial communication with GPS devices
Serial terminal on devices like Raspberry Pi