User manual

ECE 477 Final Report Spring 2004
requires the development of a communication/authentication protocol between the host and
remote devices. It must be possible for many remote devices to be in operation at the same time.
The protocol must have a way to validate received orders or request the re-transmission of an
order and the remote device must re-transmit any order if it has not received a confirmation of
that order within a certain time. A two channel transceiver will be used for the design because of
cost and design overhead, but a commercially viable system would utilize a transceiver with
more channels.
Power Supply Constraints:
The portable device will be running on batteries and therefore need to consume as little
power as possible. The microprocessor should also be chosen so that it will consume minimal
power to perform the required operations. A watchdog timer will be needed should the battery
voltage drop below its critical level or if any electromagnetic interference or electrostatic
discharge causes the microcontroller to execute erroneous instructions.
Another constraint on the handheld device is the clock speed. Since the design doesn’t
need a high computing power, a slow clock can be chosen for the design. However, we need to
be able to choose a frequency of operation that is fast enough to handle the LCD display as well
as the RF transmissions. The base station can be run on an external power supply and therefore
does not have to be subject to the same constraints as the portable unit. The computer attaches to
the RF adapter directly and therefore the power comes from the computer directly.
Packaging Constraints:
The device should be small and light as to be carried around a restaurant easily. It should
not be much bigger than an average drink coaster, but still need to have a readable display and
easy to use interface with moderately sized buttons.
Cost Constraints:
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