This is an extremely simple GUI for calculating ideal configuration register values for serial communications (UART, SPI, I2C) on Renesas RX microcontrollers.  Given the target bit rate and CPU clock, it generates the configuration register values which yield the smallest error.

Download

Source package (Visual Studio 2010 project).  Includes binaries for .NET 4 or better (see bin subdirectory), should work correctly under Mono without modification.