80 lines
4.1 KiB
TeX
80 lines
4.1 KiB
TeX
%! TEX root = ../thesis.tex
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\chapter{Introduction}
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\section{The BrainScale System}
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The BrainScale Wafer System~\cite{hbpguidebook}, developed and used in the electronic visions group at Heidelberg University is a neuromorphic hardware implementation.\\~\\
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For this thesis the following core components are of importance:
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\begin{itemize}
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\item mixed-signal ASICs, named HICANNs, structured in packs of 8 into reticles
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\item Control Units for Reticles, short CURE boards
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\item Analog Breakout boards, AnaB for short
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\item and power supply, called PowerIt.
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\end{itemize}
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\begin{figure}[H]
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\centering
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\includegraphics[width=.9\textwidth]{pics/waferscale_system.png}
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\caption{The BrainScaleS wafer-scale hardware system, marked are the main components comprising a single wafer system.~\cite{hbpguidebook-brainscales}}\label{fig:wss}
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\end{figure}
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\section{About the PowerIt Subsystem}
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The main subject of this thesis is the PowerIt board (\autoref{fig:pitteststand}). It functions as power supply inside of the WaferScale system (\autoref{fig:wss}).
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In which it is providing the wafer with \SI{1.8}{\volt} and the FPGAs with \SI{9.6}{\volt}. Its maximum rated power draw is \SI{2}{\kilo\watt}.~\cite{poweritupgrade}
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\begin{figure}[h]
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\centering
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\includegraphics[width=.7\textwidth]{pics/poweritv2_teststand_2}
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\caption{PowerIt board, top view, receiving \SI{48}{\volt} as input (
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%TODO: color
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) and outputting \SI{9.6}{\volt} (
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%TODO: color
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) as well as \SI{1.8}{\volt} (analog:
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%TODO: color
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; digital:
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%TODO: color
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)}\label{fig:pitteststand}
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\end{figure}
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The brain of these PowerIt boards is a STM32 Chip\footnote{STM32F405RGT~\cite{stm32f405xx}} which runs a custom firmware based on ChibiOS~\cite{chibios}.
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The PowerIt, while providing \SI{9.6}{\volt} and \SI{1.8}{\volt}, also is able to measure the following values:
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\begin{itemize}
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\item input voltage and current
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\item \SI{1.8}{\volt} output voltage and current
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\item and the \SI{9.6}{\volt} output Voltage
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\end{itemize}
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which can then be used inside the firmware.
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While the input voltage is given from outside it is still changeable if the power supply is able to vary its output voltage.
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Additionally the \SI{9.6}{\volt} are a set voltage obtained by the power supply modules\footnote{5:1 Bus converter IB0xxE096T48xx, 500W each}, which divide the input volatge by 5.
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Lastly the \SI{1.8}{\volt} output voltage is variable.
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\newpage
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\section{Contents in Detail}
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The first goal was to be able to change the calibration parameters.
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While this can be done at compiletime, these changes are board specific.
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Therefore they either need to be changed, before compiling, which would require a compilation per board.
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Or else the need to be able to change during runtime.
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For mainly maintainability reasons the second way was choosen.
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But these calibration changes could not be transferred to the PowerIt using the old communication protokol, referred to as PItCOMM version 1.
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A updated protocol was needed and it had to be able to accept not only the beforementioned values, but also any additional information or configuration.
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And while at it the protocol, now PItCOMM version 2, was made to be somewhat compliant with the SMBus specifications.
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This was accomplished with a virtual memory map, which maps every parameter to a specific location in a virtual memeory.
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In this memory, any value which needed to be accessible, be it measurement, calibration or static board information, is mapped (see \autoref{registerbuffer}).
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Whith this as foundation, the PowerIt could be calibrated.
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And the calibration parameters were be stored in a database.
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The Calibration characterizes the voltage measuring circuit, whose voltages are either coming into or leaving the PowerIt.
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Lastly, with a now calibrated board, a power supplys behavior was observed and corrected for, with a regulation mechanism.
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