This article shows how to use the PIC16F84 microcontroller with PicBasic to design a quick & effective, serially controlled, I/O-Expander. Using PicBasic makes developing handy single-chip devices like this extremely simple.-This article shows how to use the PIC16F84 microcontroller with PicBasic to design a quick & effective, serially controlled, I/O-Expander.　Using PicBasic makes developing handy single-chip devices like this extremely simple.