Download fulltext - DiVA Portal

14
2.3
CHAPTER 2. SPECIFICATION AND SYSTEM DESIGN
Specification
In order to choose the right hardware components and the suitable software
libraries, a detailed specification needs to be made. The specification in the
preliminary design [66] is used as a basis, with necessary changes based on results
presented in the paper.
In addition to the specific requirements for the various components of the
system, there are a few general guidelines that applies to the whole project:
Cost: All hardware components are chosen with price in mind, both for single
units for the actual cost for prototyping, and volume prices with massproduction in mind. Price and availability of components may nonetheless
end in choosing non-optimal components for prototyping.
Time: Time is a scarce resource and will affect the whole project: long lead times
are undesirable, and there is most likely only time for making one complete
prototype. Software libraries that are easy to use and eliminate need for
self-written libraries will be preferred.
This is an educational project, but some care is taken with regard to making
a commercial product. Any choices that would greatly affect the feasibility of
continue developing, finishing and mass-producing the OOD as a commercial
product are avoided when possible.
Physical dimensions
The OOD should be as small as possible. The depth should be prioritised, so
that the device do not protrude too far out of the wall it will be mounted on.
In order to achieve this, some of the bulky components can be placed so that
they are no longer directly behind the display. An small increase of the width or
height of the device is more preferable than having a thick device.
Network
The choice of network technology in the preliminary design was done along with
the choice of display and power supply. Instead of choosing to use battery as
a power source, along with an energy-efficient display and a wireless network
technology, colour LCD was chosen for display, Ethernet as network technology,
and PoE for transporting power. Ethernet is a complex network technology that
can be challenging to implement in embedded systems, but it also fulfills the most
important needs for network in the OOD: