The original Arduino board has spawned dozens of variations and from the Arduino Mini to the Arduino Lilypad, there is a huge selection to choose from. But not all of these boards have a direct USB connection, leaving it up to you to figure out the best way to connect your new board to your computer. That's where the USB 2 Serial Converter comes in.
This board converts a USB connection into a 5 volt Serial TX and RX that you can connect straight to the Arduino Mini, Arduino Ethernet or other microcontrollers, allowing them to talk to the computer. It features an Atmega8U2 programmed as a USB-to-serial converter, the same chip found on the Arduino Uno. The '8U2 firmware uses the standard USB COM drivers, and no external driver is needed(however, on Windows, a .inf file is required.)
The USB Serial Adapter has an onboard mini-USB connector and 5 pins including RX (for receiving data from the computer) and TX (for transmitting data), 5V, Ground and Reset. The 5 pin serial connector is compatible with a standard FTDI connector.
By connecting the reset line of the USB 2 Serial Converter too the reset line of your Arduino board, you can enable the automatic software reset feature. This will automatically reset your board when you initiate an upload from your computer.
Below is a list of compatible Arduino boards. However, this board will work with any 5v serial Arduino board, or as a general purpose USB to 5v serial converter.
Arduino Mini Pro
Arduino LilyPad Simple