58 lines
2 KiB
TeX
58 lines
2 KiB
TeX
\subsection{Backplane}
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To connect the modules to the microprocessor, many pins need to be connected
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straight through. For this purpose a backplane was chosen where DIN41612
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connectors can be used. These connectors were chosen for their large pin count
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(96 pins) and their availability. The backplane connects all 96-pins straight
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through. With the 6 outer left and right pins connected for VCC and ground,
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as can be seen in figure \ref{fig:schem_back_conn}.
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\begin{figure}[H]
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\includegraphics[width=\textwidth, angle=0]{schem_pdf/backplane_conn.pdf}
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\caption{Layout of the DIN41612 Connectors on the Backplane}
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\label{fig:schem_back_conn}
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\end{figure}
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\subsubsection{Termination resistors}
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In constrast to other systems using this backplane, no termination resistors
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were used. This makes the bus more prone to refelctions, however these were not
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a problem during development with the maximum transmission rate of 1MHz, as can
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be seen in the sample recording in figure \ref{fig:reflex}
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\begin{figure}[H]
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\begin{tikzpicture}
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\begin{axis}[
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ylabel=Voltage on MS1,
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xlabel=Time,
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grid=both,
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xmin = -0.000001,
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xmax = 0.000002,
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minor tick num=5,
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width=\textwidth,
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height=0.25\textheight]
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\addplot table [x=t, y=c1, col sep=comma, mark=none] {meas/20200319reflexions.csv};
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\end{axis}
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\end{tikzpicture}
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\caption{Measurement at around 1MHz bus clock on MS1}
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\label{fig:reflex}
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\end{figure}
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The ripple seen in figure \ref{fig:reflex} are most likely due to
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the sample rate of the Oszilloscope, which is around 10Mhz after an average
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filter has been applied. The measurement was performed on the finished project,
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with all cards installed.
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\subsection{Case}
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The case for the backplane was provided by the hackerspace, and is meant for
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installation in a rack. The case is meant for installation of cards in the
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EUROCARD format, therfore all modules were built by this formfactor.
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\begin{figure}[H]
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\includegraphics[width=\textwidth, angle=0]{pics/case}
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\caption{The case with installed backplane}
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\label{fig:case}
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\end{figure}
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