\subsection{Testing and Measurement}

For functional testing and verification of implementation goals measurements
needed to be performed in various different ways, and testing software was
required.

\subsubsection{Measurements}

Measurements were performed, if not noted otherwise, with the Analog Discovery
2 from Digilent as it has 16bit digital I/O Pins as well a a Waveform generator
and 2 differential oszilloscope inputs\cite{ad2}. These were enough for all 
nescessary measurements. Though due to the size and construction of the device,
which can be seen in figure \ref{fig:ad2},
errors were encountered while performing the measurements. These are noted on 
occurance.

\begin{figure}[H]
	\centering
	\includegraphics[width=.6\textwidth, angle=0]{pics/ad2}
	\caption{Digilent Analog Discovery 2;Source: \url{https://www.sparkfun.com/}}
	\label{fig:ad2}
\end{figure}

\subsubsection{Testing}

All testing was performed with an Atmel ATMega2560 due to it's large amount
of I/O pins, 5V I/O, which is the more common voltage level on CMOS
peripherals, way of addressing pins (8 at a time) and availability.
\cite{atmega2560} All 
testing software was written for this ATMega and compiled using the avr-gcc 
from the GNU-Project.

To fully test the developed modules on the backplane a seprate module for the
ATMega was developed, which can be seen in figure \ref{fig:atmega_mod}. The
ATMega is beneath the the black PCB \footnote{Printed circuit board} in the 
center, which is an Arduino\texttrademark Mega. The Arduino\texttrademark is, 
for all indends and purposes, only a breakout of the ATMega 2560 and has only
been used in that way. No parts of the Arduino\texttrademark IDE or other parts
of the Arduino\texttrademark software suite have been used, as they consume too
much memory and the abstraction models used are not compatiable with building
processor peripherals.

\begin{figure}[H]
	\centering
	\includegraphics[width=\textwidth, angle=0]{pics/atmega}
	\caption{The ATMega 2560 module for the backplane}
	\label{fig:atmega_mod}
\end{figure}