I used to make test systems of electronic components with GPIO, GPIB, and air cylinders. But we could test only very simple components. We are required to test pretty complex components including I2C I/F these days. We searched for suitable solution. I found that PC serial ports control micro controllers which control DUTs via I2C and such systems can easily be implementd by reading this book. Using new PC without serial port, we can use same system by adding USB virtual COM port. I thank the author for giving me recent knowledge about serial port links.