A little project with not much use. The circuit connects to the PC:s USB-port via V-USB. It also connects to the serial port via RS232. The PC-code can send two different messages to the AVR (ATTiny2313) via USB, the AVR responds by sending one of two messages to the PC's serial port. This device is powered from USB, no external powersource is used.
The point? It can be used in testing, where debug-messages are sent to the serial port.