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signals would not pass. This assumption proved to be wrong as it would still degrade
the signal existing in the other switching device. With the HEF4066 left powered up
and the enables held to Gnd when a separation of data lines is required, the system
works as it is supposed to.
7.2 Results
The electronic class schedule performs as it was designed. The user may select one of
five buttons and receive the respective picture file on the screen. Designing the system
to handle larger size picture files could enhance the experience for the user. Though
the existing file size of 3 KB is sufficient to deliver the material, as of now files larger
than 10 KB take too much time to transfer and run a greater risk of losing data. The
system can provide an easy way for teachers to put their schedules to the appropriate
rooms without having to travel around the school changing out paper schedules. This
also includes writing extra comments. For example, if a class is cancelled or moved to
another room, this information can be added to the online schedule for the electronic
class schedule to parse and display for users. There are many other improvements that
future students may add as well to ensure that the electronic class schedule is
developed to its full potential.
7.3 Future Development
The speed of the system was limited by the read and write operations of both the
UART connection to the WiFly and the SPI connection to the SD card. During
development the UART connection was tested to run best at the speed of 14400 bps.
The initialization of the SD card must be below 400 KHz, but it can be stepped up
for data transfer. For this project the data rate was only stepped up to 700 KHz, as the
files are around 3 Kb in size. The total transfer from WiFly to SD card takes a little over
two seconds. Future models of the WiFly unit will include SPI connection, being several
times faster than UART, which will effectively speed up the delivery of data. When
these become available, the speed of the data transfer can be increased enabling the
picture files to be larger and of better quality.
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