The One-Pin UART is said to convert a single I/O pin of a MCU/MPU into an efficient RS-232 test port without stealing valuable resources and without adding to the production cost of the product. The device is targeted at MCU/MPU-based products where software tools create the need for an additional serial port during development, production testing and subsequent maintenance.The single I/O pin can handle all the necessary handshaking and transfer of data to achieve a high-speed, bi-directional interface. A buffer is used between that interface and the RS-232 test port to allow some independence of operation. Connections are made using a test clip for the I/O pin and a DB25 connector for the test port. Only a small amount of target code space is required in addition to the one I/O pin.