199 lines
7.1 KiB
TeX
199 lines
7.1 KiB
TeX
\subsection{Hardware peripherals}
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Planning of the peripherals was done based on the information provided on large
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parts by David Oberhollenzer. A lot of his advice contributed heavily to the
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direction the development went.
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\subsubsection{Peripheral selection}
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The selection of the hardware peripherals was done based on implementation
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difficulty, common use in computer systems, relevance in current times and
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whether they were fitting for demonstrative purposes.
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\paragraph{Serial Communication interface}
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Serial communication interfaces have been around for a long time. They have been
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used for many different applications from early mouse pointer devices
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\cite{232mouse} to user input terminals\cite{vt100}
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which are far away from the real computer system. They are still very common in
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smaller embedded systems and in the server space, where they are used as a
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simple
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and less error prone way to interface with the operating system and programs
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running there. They are fairly easy to implement as there are interface
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ICs which provide a more generic interface for serial communications
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\cite{pc16550}. Most SOCs
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\footnote{SOC... System on a Chip} have some form of serial communication
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interface. The most common serial interface voltages are 3.3V, 5V and levels
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as per TIA-/EIA-232 specification\cite{rs232}.
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\paragraph{Parallel Port interface}
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Parallel ports are absent on most modern computer systems but historically have
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been the high speed interfaces on computers. Early computer systems used
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parallel-ports for expansions and the ISA-Bus
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\footnote{ISA...Industry Standard Architecture} was for some time the main way
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of expansion for PCs
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\footnote{PC in this thesis referrs to Computer Systems using the x86
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Architecture}. Most younger people remember parallel ports as the port for
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printers on their home PCs. A parallel port is easy to implement because it has
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simmilar use of control, data and address lines as a processor uses internally
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anyway\cite{laval_parallel}. Usage of the standard IEEE 1284 port limits the
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design to the signals on this port or makes the use of the signals on this port
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obligatory.
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\paragraph{Digital to Analog Converter}
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Digital to Analog Converters (or more commonly DACs) are used on all modern PCs
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for sound output. They have been around for longer and some external sound card
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interfaces have been standardised like AC '97\cite{ac97}. Implementation of a
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standard audio interface requires higher speed connections or more precise
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timing for ac97 for example. Earlier computer systems did not have a sound card
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as it doesn't have important usage for computing and user input tasks and later
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on computer systems only had a PC speaker for diagnostics such as the IBM PC AT
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\cite{ibmpc} which can only procude one specific frequency and does not have a
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DAC. A DAC is not easy to implement as it requires a constant sampling rate and
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a buffer to be of any practical use.
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\paragraph{Graphical output / GPU}
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Graphical output on older computer systems such as the EDVAC
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\cite{neumann} was not possible because it requires
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either a heavy load on the processor or dedicated hardware and due to the mostly
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scientific use it was easier to just print the caracters as letters via a
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printer. Drawing characters
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onto a screen is by itself not an easy task as it requires, for example for
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VGA, a Digital to Analog Converter with 25MHz sampling rate and a buffer to
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contain all needed data for one frame or at least parts of it, while the CPU
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renders the frame\cite{vga}. Screen output is one of the, if not the most,
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common form of output on a computer today.
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\paragraph{Inter Integrated Circuit}
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Inter Integrated Circuit or IIC for short is a standard for serial transmission
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between Integrated circuits\cite{iic}. This is done on a master-slave basis and
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transmission speed is fairly low in standard 100kBit/s mode. The bus is used
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on many different platforms for many different things including HDMI DDC
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\cite{ddc}. Though there are some IIC ICs which can interface with a parallel
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bus such as the PCA9564 \cite{pca9564} but these are either limited in
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capability or not easy to use and implement. Most people don't have an
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understanding of IIC as it is only known in technical fields.
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\paragraph{Utility analysis}
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Among the above mentioned processor peripherals from the criteria mentioned
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before a utility analysis was performed. To do this, different points have been
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credited for the criteria mentioned which can be seen in Table
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\ref{tab:utility_base}. The multipliers in Table \ref{tab:utility_base} have
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been applied to the points and the sums in Table \ref{tab:utility_result}
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resulted. Based on this
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result the DAC and Serial Communication interface were chosen as peripherals.
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\begin{table}[H]
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\centering
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\resizebox{\textwidth}{!}{
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\begin{tabular}{ |l||c|c|c|c|c|}
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\hline
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Criteria & serial port & parallel port & DAC & GPU & IIC\\
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\hline
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\hline
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implementation & 0 & 0 & 1 & 4 & 2\\
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\hline
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common use & 2 & 1 & 3 & 3 & 1\\
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\hline
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relevance & 2 & 1 & 3 & 3 & 1\\
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\hline
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demonstrative & 2 & 1 & 3 & 2 & 1\\
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\hline
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\end{tabular}
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}
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\caption{utility analysis base points for peripherals}
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\label{tab:utility_base}
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\end{table}
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\begin{table}[H]
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\centering
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\begin{tabular}{ |l|c|}
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\hline
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Criteria & multiplier \\
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\hline
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\hline
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implementation & -2\\
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\hline
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common use & 1\\
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\hline
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relevance & 2\\
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\hline
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demonstrative & 3\\
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\hline
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\end{tabular}
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\caption{utility analysis multipliers for peripherals}
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\label{tab:utility_mul}
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\end{table}
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\begin{table}[H]
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\centering
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\resizebox{\textwidth}{!}{
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\begin{tabular}{ |l||c|c|c|c|c|}
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\hline
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Criteria & serial port & parallel port & DAC & GPU & IIC\\
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\hline
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\hline
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implementation & 0 & 0 & -2 & -8 & -4\\
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\hline
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common use & 2 & 1 & 3 & 3 & 1\\
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\hline
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relevance & 4 & 2 & 6 & 6 & 2\\
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\hline
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demonstrative & 6 & 3 & 9 & 6 & 3\\
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\hline
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\hline
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\textbf{SUM} & 12 & 6 & 16 & 7 & 2\\
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\hline
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\hline
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\end{tabular}
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}
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\caption{utility analysis results for peripherals}
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\label{tab:utility_result}
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\end{table}
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\subsubsection{Material and Infrastructure cost}
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The peripherals were mostly constructed with materials currently in stock at
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the Hackerspace Innsbruck. This limitation, while driving development time up,
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reduced the material cost significantly as resistors, capacitors and most
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standard logic ICs were in stock for the purpose of such projects. The materials
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which had to be ordered and were used in the final implementation of the
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peripherals are listed in Table \ref{tab:cost_hw}. Infrastructure usage at the
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Hackerspace is unlimted to anyone who is working on a project and a member of
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the community and free of charge.
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\begin{table}[H]
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\centering
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\resizebox{\textwidth}{!}{
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\begin{tabular}{ |l|c|c|}
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\hline
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\textbf{Name} & \textbf{Cost} & \textbf{Quantity}\\
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\hline
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\hline
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ADC 8bit RS-COMPONENTS & € 4.16 &3\\
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\hline
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8-bit D-Latch RS-COMPONENTS & € 2.21 &4\\
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\hline
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MAX232 RS-COMPONENTS & € 2.19 &2\\
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\hline
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Quartz, 1,8432 MHz POLLIN & € 0.15 &4\\
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\hline
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\hline
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\end{tabular}
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}
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\caption{List of ordered components and cost}
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\label{tab:cost_hw}
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\end{table}
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