This adapter allows connecting micro-controller boards that have 5V or 3.3V serial interfaces to a PC USB port. The converter is compatible with FTDI USB TTL Serial cables and SparkFun FTDI Basic breakout board. Compared to SparkFun board, uses much more reliable and common nowadays Micro USB connector. It is also cheaper to make (about $7 per board), and so it makes a nice project for practicing your SMD soldering skills :-).
The board is based on FTDI FT231X chip. It provides RS-232 RX and TX signals, as well as DTR and CTS signals that are used by Arduino-like boards for resetting the microcontroller before uploading the code. The board schematic is available in the file section at the bottom of this page.
The board supports either 5V or 3.3V logic levels. It is pre-configured for 5V. To configured for 3.3V cut the trace between pins 2 and 3 of JP1/PWR_SEL on the bottom side of the board, and connect pins 1 and 2 together.
Link to the project on Mouser.com - View and order all components except of PCB.
Link to the project on OSHPark.com - View and order PCB.