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PROGRAMMED BRAINS 433

Communications Interconnectivity
Not long ago, computers came with a variety of external ports for connecting things to them:
parallel ports for printers, serial ports for phone modems, and game ports for joysticks— among
others. All these provided fairly easy ways to connect the computer to robot hardware.
Today, the typical PC lacks all three. Instead, it relies almost entirely on the all- purpose
USB port. That’s okay, as USB is a flexible system and cables for it are inexpensive. But it
also means you need to get an adapter to convert the fairly sophisticated USB signals from
your PC to a form you can readily use with your robot. These adapters change USB ports into
parallel or serial ports. They’re commonly available from online electronics parts outlets; refer
to Appendix B, “Internet Parts Sources,” for a list of popular Web- based stores.

Data Storage
Whatever your type of PC, you need some means to store your programs and other important
data. Notebook and netbook computers already have this solved; they come with their own
compact drives, either hard disk or solid state.
If using a mini- ITX motherboard by itself, you can pick from a variety of mass data storage
options:

• Flash drive. This appears to the mini- ITX as a standard hard drive, but it actually contains
no moving parts. It’s all flash memory in there. Data capacities are somewhat low when
compared to traditional hard drives, and the cost is more. But flash drives are quiet and
weigh next to nothing, and they aren’t damaged if the robot suddenly falls over.
• Small- profile (2.5″) hard drive. When you need lots of data space, nothing beats a hard
drive. These are compact models made to take up little room. Because they contain a spin-
ning disk drive, you must be careful when using them on mobile robots.
• USB hard drive or thumbdrive. Via the USB port on the motherboard you can connect
any of a number of mass media drives, including compact hard drives and small thumb
drives. When selecting a compact hard drive, get one that derives its power from the USB
port itself. You don’t want the kind that needs to be plugged into a wall outlet.

G In order to use a USB hard drive or flash drive, you must be sure the motherboard can boot
(start) from the USB drive. Most can, but you’ll want to make sure before you purchase any new
board.

Using an Off- Bot PC
Tabletop and teleoperated robots can be controlled with a separate PC. An example of a
tabletop robot is a stationary arm. These can readily be connected to the host computer via a
USB cable. Unless the arm has its own USB jack on it, you’ll need a USB- to- serial or
USB- to- parallel adapter.
Teleoperated robots can also use wireless communication. There are literally dozens of
off- the- shelf standardized solutions for connecting devices (including robots) through the air-
waves, including Bluetooth, 802.15.4 Zigbee, and 802.11 Wi- Fi. From your desktop or lap-
top PC, you connect to a wireless transceiver through a standard USB port. That transceiver
communicates with another transceiver on your robot. This second transceiver can then con-
trol motors, operate a remote camera, even send back video signals to your computer.
If going this route, you can choose between half- duplex and full- duplex communications.
With half- duplex, only one side can talk at a time. For example, you can command your robot,
but it can’t send back information at the same time. For greatest flexibility, you want full- duplex

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