80 lines
4.7 KiB
TeX
80 lines
4.7 KiB
TeX
%! TEX root = ../thesis.tex
|
|
|
|
|
|
\chapter{Introduction}
|
|
|
|
This will be a short introduction to the BrainScaleS System and PowerIt.
|
|
|
|
\section{The BrainScaleS System}
|
|
|
|
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}.
|
|
On this hardware, mixed-signal ASICs, or also called HICANNs\footnote{High Input Count Analog Neural Network}, implement a behavior similar to that of a neuron found in biological systems.
|
|
These ASIC chips are placed on a silicon wafer, and grouped into packs of 8, called reticles.
|
|
With these chips complex behaviors of biological systems can be simulated.
|
|
|
|
Focus of this thesis is part of the hardware implementation and only the following components will either be further examined or used later on:
|
|
|
|
\begin{itemize}
|
|
\item Control Units for Reticles, short CURE boards
|
|
|
|
These boards control the power delivery mechanism for each of the 48 reticles.
|
|
\item Analog Breakout boards, AnaB for short
|
|
|
|
Provided by these boards are direct connections to reticle voltages, two per reticle. These are normally shared between all 8 reticles.
|
|
\item and its power supply, called PowerIt.
|
|
\end{itemize}
|
|
|
|
\begin{figure}[H]
|
|
\centering
|
|
\includegraphics[width=.7\textwidth]{pics/waferscale_system.png}
|
|
\caption{The BrainScaleS wafer-scale hardware system, marked are the main components comprising a single wafer system.~\cite{hbpguidebook-brainscales}}\label{fig:wss}
|
|
\end{figure}
|
|
|
|
\section{About the PowerIt Subsystem}
|
|
|
|
The main subject of this thesis is the PowerIt board, photographed in \autoref{fig:pitteststand}. It functions as power supply inside of the wafer-scale 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}
|
|
|
|
\begin{figure}[h]
|
|
\centering
|
|
\includegraphics[width=.7\textwidth]{./tikz/powerit.pdf}
|
|
\caption{
|
|
Photograph of the PowerIt boards top view.
|
|
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}
|
|
\end{figure}
|
|
|
|
This PowerIt board has a integrated STM32 microcontroller\footnote{STM32F405RGT~\cite{stm32f405xx}} which runs a custom firmware based on ChibiOS~\cite{chibios}.
|
|
For this thesis import ant is, that the chip runs at \SI{169}{\mega\hertz}.
|
|
Note that of its internal components mainly a 12bit ADC is used.
|
|
It is clocked with the same internal frequency as the processor.
|
|
|
|
The PowerIt measures the following values via the STM32-internal ADC:
|
|
|
|
\begin{itemize}
|
|
\item input voltage and current
|
|
\item \SI{1.8}{\volt} output voltage and current each for analog and digital circuitry
|
|
\item and the \SI{9.6}{\volt} output voltage
|
|
\end{itemize}
|
|
|
|
which can then be used inside the firmware and read from devices via the I\(^2\)C connection.
|
|
The external device can then get this information from the PowerIt to the BrainScaleS monitoring system.
|
|
|
|
The input voltage, nominal, is \SI{48}{\volt} and therefore the input current should not exceed \SI{41.7}{\ampere}
|
|
Additionally the \SI{9.6}{\volt} are a set voltage obtained by the power supply modules\footnote{5:1 Bus converter IB0xxE096T48xx, 500W each~\cite{vicormods}} which divide the input voltage by 5.
|
|
Lastly the \SI{1.8}{\volt} output voltage is variable.
|
|
|
|
\newpage
|
|
\section{Contents in Detail}
|
|
|
|
The first goal was to be able to change the calibration parameters.
|
|
An upgrade for the PowerIt firmware was added to accomodate for those values.
|
|
This was accomplished with a virtual memory map, which maps every parameter to a specific location and all of them can be changed.\\
|
|
|
|
Calibrating the PowerIt was the next task.
|
|
The calibration characterizes the voltage measuring circuits, whose voltages are either coming into or leaving the PowerIt.
|
|
Additionally there are current measuring circuits for incoming current and both \SI{1.8}{\volt} output currents.
|
|
A reference voltage measurement was used to generate fitted polynomials.
|
|
These polynomials coefficients are the calibration parameters used inside the PowerIt.
|
|
|
|
Taking these calibrations as basis, the \SI{1.8}{\volt} power supplies' behavior through different current draws could be observed.
|
|
A simple model was generated from these measurements and applied.
|
|
Also inmplemented inside the firmware was a first iteration of that model which could now be tested. |