User manual

ECE 477 Final Report Spring 2004
8.0 Schematic Design Considerations
The goal of our project is to design a wireless ordering device (WOrD) which will allow
a customer to view limited menus and possibly other information at a commercial establishment
(e.g. a restaurant or bar). The end purpose of this project is to allow a patron of a restaurant to be
able to order drinks and appetizers while they wait for a table and have their order waiting for
them as they are seated. A transceiver connected to a host computer’s serial port will serve as a
base station transmitting menus and other information to the remote devices via an RF
transceiver. Each remote device will enable a user to navigate the menu and place orders which
will be sent to the host computer. A bank of LEDs will illuminate on the remote device when the
host computer alerts it that the user’s table is ready. Each remote device’s interface will include
an LCD display, menu navigation buttons and a bank of LEDs.
An asynchronous RF transceiver will be used to allow communication between the host
computer and remote devices. This allows for a low-power, relatively simple hardware
implementation. It is possible to use a single chip solution with a printed antenna to minimize
board and package size. A 128x128 graphic LCD display [7-1] will be used to display and
navigate menu information. The viewing area allows for a user to easily read the menu without
the need for scrolling. The LCD display allows for 16 lines of 22 characters, this is ample for
multiple level menus as well as food price and information. The LCD driver contains an 8K
SRAM module, allowing ample room to store menu text and graphics. Because the LCD module
uses 5V logic, the remote device will be powered by a 6V battery pack.
Theory of Operation
The microcontroller on both the host computer and remote device is the Atmel
ATmega162V [1]. The ATmega162V can operate at both 3.3V and 5V logic. The remote
device requires the 3.3V level for lower power consumption, it also needs the large number of
I/O pins to interface with the RF transceiver, LCD module and navigation buttons. The remote
device’s microcontroller can be operated at 3.3V and 1MHz to lower power consumption. The
ATmega162V also has dual USARTs which the base station requires to interface with both the
PC and remote devices. The primary function of the remote device’s microcontroller is to relay
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