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ECE 477 Final Report Spring 2004
down system components, trying to find low power dissipation parts that operated at the 3.3V
level that was ideal for the design. It was my goal to have the final remote device package small
enough to be easily held and operated while still allowing for a large information viewing area.
I was responsible for the circuit design and theory of operation homework. This involved
creating the project schematic from the list of components the group had selected. During the
creation of the schematic, the data sheets for each component had to be studied thoroughly to
understand how each component interacted with the others. Before the schematic was finished,
the RS232 to 3.3V logic converter solution had to be changed and a -15V supply for the LCD
module had to be created. The only flaw in the schematic was the inclusion of button
debouncers, which were discarded in favor of software debouncing. Virtually no fly-wiring was
needed to successfully finish the project.
Though not primarily responsible for PCB layout, I contributed many hours toward the
creation of final PCB. My intimate understanding of the device schematics helped me to
organize the components into functional blocks to simplify trace routing. I helped route a
portion of both the base station and remote device layouts.
As the project was built up incrementally, I helped test functionality by testing traces and
using the oscilloscope to confirm heartbeat programs. I helped troubleshoot the problems with
the -15V supply. My studying of the data sheets narrowed down the problem, a larger inductor
was used and the power supply worked successfully. I also suggested that testing the clock of
our inoperative microcontroller might indicate if it was broken or not. I spent several hours
agonizing over the failed RF circuit. I contacted Atmel customer support and studied the data
sheets to no avail. I also trouble shot the communication problem between the base station and
remote device by theorizing that the significant difference in their clock speeds might create
enough disparity in packet generation and detection to cause the remote device to incorrectly
interpret the packets. Once the two clocks were calibrated, the two microcontrollers
communicated flawlessly.
Getting the hardware running was a true milestone. Once the physical aspect of the
design was finished, programming the firmware was quickly accomplished. I helped create the
communication protocol the project used, modeling it after the internet protocol. I programmed
the base station to transmit packets to the appropriate destinations and drop packets with bad
checksums, similar to a router on a network. I programmed the remote device to accept packets
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