Making Things Talk

148 MAKING THINGS TALK

Interactive Systems and Feedback Loops

For example, in the cat bed application in Chapter 3,

there’s no need for the system to respond in more than

a few seconds, because your reaction is not very time-

sensitive. As long as you get to see the cat while he’s on

the bed (which may be true for several minutes or hours),

you’re happy. Monski pong in Chapter 2 relies on a reason-

ably tight feedback loop in order to be fun. If it took a half

second or more for the paddles to move when you move

Monski’s arms, it’d be no fun. The timing of the feedback

loop depends on the shortest time that matters to the

participant.

Any system that requires coordination between action and

reaction needs a tight feedback loop. Consider remote

control systems, for example. Perhaps you’re building a

robot that’s operated over a network. In that case, you’d

need not only a fast network for the control system, but

also a fast response from the camera or sensors on the

robot (or in its environment) that are giving you informa-

tion about what’s happening. You need to be able to both

control it quickly and see the results quickly. Networked

action games also need a fast network. It’s no fun if your

game console reacts slowly, allowing other players with

a faster network connection to get the jump on you. For

applications like this, an exchange protocol that’s con-

stantly opening and closing ...