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The Microcontroller Idea Book - Jan Axelson's Lakeview Research

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Wireless Links<br />

12<br />

Wireless Links<br />

Wires and cables are by far the most common way to connect one circuit to another, but<br />

wireless links are another option. Sometimes a wireless connection is more flexible,<br />

convenient, or practical, because you don’t have to string wires from point to point.<br />

On an 8052-BASIC system, you can use a wireless link to send commands to devices that<br />

recognize and act on them. Or, in the other direction, the devices might transmit to an<br />

8052-BASIC system that acts on the information received. Or you can have two 8052-BA-<br />

SIC systems that communicate with each other over the wireless link.<br />

This chapter describes ways to do these, using infrared energy or radio waves as the<br />

transmitting medium.<br />

Infrared Links<br />

Over short distances and at lower speeds, infrared is a good choice for wireless links. Figures<br />

12-1 and 12-2 show a link whose transmitter sends 4-bit messages to one or more receivers.<br />

Each receiver has a 5-bit address, which enables the transmitter to send a message to a<br />

selected receiver, while other receivers will ignore it.<br />

<strong>The</strong>se circuits are independent modules controlled by manual switches or jumpers, rather<br />

than by a microcontroller. This is a good way to get the link up and running. When that’s<br />

<strong>The</strong> <strong>Microcontroller</strong> <strong>Idea</strong> <strong>Book</strong> 199

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