The need often arises to make use of a serial port in connection with a microcontroller thatdoes not have a hardware UART on-chip. Aside from the obvious cases where themicrocontroller application intrinsically requires RS-232 communications to achieve its purpose, a serial output may often be a simple and convenient method of providingdetailed diagnostic information to the outside world while using only a single I/O port pin. Inmany cases, the solution may be to implement the UART function in software.The routines included here demonstrate a method to add such a function to a microcontroller without the benefit of a hardware UART.