78 lines
4.4 KiB
TeX
78 lines
4.4 KiB
TeX
%! TEX root = ../thesis.tex
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\chapter{Introduction}
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This will be a short introduction to the BrainScaleS System and PowerIt.
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\section{The BrainScaleS System}
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The BrainScaleS Wafer System which is visualized in \autoref{fig:wss}, developed and used in the electronic visions group at Heidelberg University is a neuromorphic hardware implementation~\cite{waferembedding}.
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On this Hardware, mixed-signal ASICs, or also called HICANNs, implement a behavior similar to that of a neuron found in biological systems.
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These ASIC chips are placed on a silicon wafer, and grouped into packs of 8, called reticles.
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With these Chips complex behavior of biological systems can be simulated.
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Focus of this thesis is part of the hardware implementation and only the following components will either be further examined or used later on:
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\begin{itemize}
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\item Control Units for Reticles, short CURe boards
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These boards control the power delivery mechanism for each of the 48 reticles.
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\item Analog Breakout boards, AnaB for short
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Provided by these boards are direct connections to reticle voltages, two per reticle. These are normally shared between all 8 reticles.
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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=.7\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, photographed in \autoref{fig:pitteststand}. It functions as power supply inside of the WaferScale system, described before, in which it provides e.g. 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]{./tikz/powerit.pdf}
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\caption{
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Photograph of the PowerIt boards top view.
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It receives \SI{48}{\volt} as input (magenta) and provides \SI{9.6}{\volt} (green) and \SI{1.8}{\volt} (analog: red, digital: blue)}\label{fig:pitteststand}
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\end{figure}
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This PowerIt board has a integrated STM32 microcontroller\footnote{STM32F405RGT~\cite{stm32f405xx}} which runs a custom firmware based on ChibiOS~\cite{chibios}.
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The PowerIt also measures 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 each for analog and digital parts of the wafer circuits
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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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The input voltage, nominal, is \SI{48}{\volt} and therefore the input current should not exceed \SI{41.7}{\ampere}
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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 voltage 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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An upgrade for the PowerIt firmware was added to accomodate for those values.
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This was accomplished with a virtual memory map, which maps every parameter to a specific location and all of them can be changed.\\
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Calibrating the PowerIt was the next task.
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The calibration characterizes the voltage measuring circuits, whose voltages are either coming into or leaving the PowerIt.
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Additionally there are a current measuring circuits for incoming current and both \SI{1.8}{\volt} output currents.
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A reference voltage measurement was used to generate a fitted polynomial.
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This polynomials coefficients are the calibration parameters used inside the PowerIt.
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Taking these calibrations as basis, the \SI{1.8}{\volt} power supplies' behavior through different current draws could be observed.
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A simple model was generated from these measurements and applied.
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Also inside the formware a first iteration of that model was implemented and could now be tested.
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This all resulted in the testing and quntification of the regulation mechanism, as well as a secondary model that could be used in the future. |