Specifications
Chapter 4 – The development platform
When planning how to implement this device it quickly became apparent that it would
require far too much time (beyond the time available for thesis) to design and construct
it from raw components. So the first stage of the implementation was to investigate
which components had already been developed and which components requiring
development.
From the beginning of this thesis the main area of focus was on the software
development either in an embedded environment or on a PC; therefore, a suitable
embedded system platform had to be found to develop the software.
4.1 Platform requirements
The project can be broken into the following functional units. The main component is a
microcontroller that runs an operating system and a TCP/IP stack. It interfaces with a
hardware network interface and MP3 decoder and has enough memory to manage the
buffer requirements of the network interface and MP3 decoder.
When searching for this platform hardware a few basic requirements were considered
important. It must be able to decode MP3 data in hardware. A decision was made that
this is to be done on an integrated circuit that is separate from the microcontroller.
Separation of these components allows reduction in cost and processing power, as the
processor does not have to decode the data into audio. The microcontroller has to be
capable of interfacing with a network physical layer and the MP3 decoder. It has to be
fast enough to transfer data through the network to the MP3 decoder and have enough
power left to process controls and a display. There must be enough storage space to
make a sufficient MP3 buffer. It was decided that approximately 2 seconds of audio
buffer would be all that is needed, equating to about 25Kbytes of RAM. Most players
normally buffer larger amounts than this because they are dealing with shock and
movement related issues. This player is not aimed as a portable player and nor will it
have any moving parts. The buffer that was used was to allow for variations in network
traffic and processing capabilities of the microcontroller. The selection of the network
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