Devices can transmit data over distances of up to 100
meters and at speeds of up to 3 Mbps. Bluetooth uses the 2.4-GHz band with
spread-spectrum technology. Up to eight Bluetooth devices can communicate
with each other in a collection called a piconet.
Bluetooth Profiles define higher-level protocols for specific functions. The
Serial Port Profile supports COM-port emulation.
A7 Engineering, Inc. (www.a7eng.com) is a source for Bluetooth modules with
asynchronous serial interfaces. The eb501-SER module can interface directly to
an RS-232, 5V, or 3V asynchronous serial port. The device firmware supports
Table 8-1: Wireless systems can use standard protocols to carry data.
" +
%( 6 % (
Bluetooth 3M 100
Zigbee 250k 50, extendable with routers
Wi-Fi 54M 40 or more
Chapter 8
154
two modes. In one mode, the modules configure themselves automatically on
powering up. The computers that interface to the modules can communicate as
if they had a wired connection with no software changes required. In the other
mode, the computers that interface to the modules can use plain-text commands
to configure and control the interfaces.
3-.
Another option for asynchronous serial data is to use a serial server with a Wi-Fi
(IEEE 802.11b or other wireless-network) interface as described in Chapter 3.
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