Hardware Hacking Projects for Geeks

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In Chapter 10, How to Build an Internet Toaster, I use several wires to

send and receive serial data so that the toaster could communicate with the

controlling PC. As you hack your own projects, your circuit may need to

communicate with other items. Wired and wireless methods are available.

Let’s take a look at the options.

Wired

One of the least expensive ways to allow two CPUs to communicate is by

connecting a set of wires between them. If the CPUs are a few inches apart,

they can have wires connected directly. If they are farther apart, a direct

connection will not work well due to noise picked up by the longer wires.

To alleviate this problem, I’ll cover several standards for medium range (1

to 100 feet) and for long range (more than 100 feet).

RS-232

The RS-232 standard is one of the oldest and most enduring bit-serial data

interfaces. It was originally used to allow video and teletype terminals to

communicate with a mainframe computer and modems. It can effectively

allow two machines to communicate up to distances of 100 feet at speeds

from 300 bits per second to 115,000 bits per second. This standard is still

in use today to connect a personal computer to modems, printers, and other

peripherals.

Many CPU and microcontrollers include hardware for an RS-232 connec-

tion. These engines are called Universal Asynchronous Receiver Transmitters

(UART