Specifications

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3.2.10 Removable Flash Memory Module
This module is present to satisfy the requirement that a common flash memory card
interface be supported in this project. Possible memory cards available for consideration
are: CF, MS, SD/MMC, and xD. The type of memory card used must sup port an auto-
detect feature when cards are inserted in the memory slot, capacities of 128MB to 2GB,
and interface using SPI. The selected card type should be easily accessible by the public
and cost less than $30.00 dollars. Lastly, the card type needs to support hot-insertion and
removal.
3.2.11 User Interface Module
The general r equirements state that the device must have an LC D-dr iven user interface
that simply and quickly allows a user verify correct operation and access device configu-
rations. In conjunction with the display, 10 push buttons must be included to navigate
through screens. These buttons must support push/hold button interpretation for slow-fast
behavior for scrolling and field editing. The screen must be easy to read/interpret and avoid
cryptic readouts. Consideration must be taken for future multi-language support.
3.3 Firmware Breakdown
The design of the firmware was also done in a modular fashion. However, the delimita-
tion of the firmware modules was not done strictly based on a functional breakdown of the
system requirements. Instead, it was based on how much hardware detail was needed to
execute an operation or perform a specific function. The varying amounts of detail placed
different operations into different layers. These layers, depicted in fig. 3.2, are as follows:
hardware abs tr action layer (green), memory management layer (blue), networking layer
(yellow), operating system layer (red), and the application layer (purple). The purpose
for a design like this is portability. The code written for this project can be used in the
future for other projects. This frees up a future designer to pick hardware without strongly
considering previous projects. Specifics of these layers and how they help satisfy the overall
design requirements is contained in sections 3.3.1 to 3.3.7.