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