Page 75 - Hacking Roomba

56 Part I — Interfacing

FIGURE 3-13: The circuit in a nifty blue enclosure made from a dental floss container

Connecting to a Computer

The serial tether has a standard RS-232C DB-9 serial port connector on it and many PCs
(older ones anyway) have these serial ports on their motherboards. It’s tempting to just plug in
the tether and start going at it. However, because in this chapter you’re going to try to avoid
breaking things, it’s instead prudent to use a USB serial adapter to guard against any bad volt-
ages entering your computer. No-name USB serial adapters can be had for less than $10 online
and so offer a cheap kind of protection for this and any future serial port–based projects you
may build.

In this book, the Keyspan US-19HS USB serial adapter will be used (see Figure 3-14). Unlike
some of the cheaper adapters, the Keyspan works on all operating systems and has never given
me any trouble, unlike some of the more generic ones I’ve used.
All of these USB serial adapters require drivers to be installed. These are very minor drivers
that won’t mess up your system.