X-Git-Url: https://bilbo.iut-bm.univ-fcomte.fr/and/gitweb/dmems12.git/blobdiff_plain/345031161b496f25408c29c01bbca3a77157de9f..c482d536e2ec5b766bfa6368469c810f7798f3f7:/dmems12.tex

diff --git a/dmems12.tex b/dmems12.tex
index 93d7fbc..314368e 100644
--- a/dmems12.tex
+++ b/dmems12.tex
@@ -245,14 +245,16 @@ CPU. But this is not the case for phase computation that used only few
 tenth of values.\\
 
 In order to evaluate the original algorithm, we translated it in C
-language. Profiles are read from a 1Mo file, as if it was an image
-stored in a device file representing the camera. The file contains 100
-profiles of 21 pixels, equally scattered in the file. We obtained an
-average of 10.5$\mu$s by profile (including I/O accesses). It is under
-are requirements but close to the limit. In case of an occasional load
-of the system, it could be largely overtaken. A solution would be to
-use a real-time operating system but another one to search for a more
-efficient algorithm.
+language. As said further, for 20 pixels, it does about 1550
+operations, thus an estimated execution time of $1550/155
+=$10$\mu$s. For a more realistic evaluation, we constructed a file of
+1Mo containing 200 profiles of 20 pixels, equally scattered. This file
+is equivalent to an image stored in a device file representing the
+camera. We obtained an average of 10.5$\mu$s by profile (including I/O
+accesses). It is under are requirements but close to the limit. In
+case of an occasional load of the system, it could be largely
+overtaken. A solution would be to use a real-time operating system but
+another one to search for a more efficient algorithm.
 
 But the main drawback is the latency of such a solution : since each
 profile must be treated one after another, the deflection of 100
@@ -278,40 +280,45 @@ some hardware constraints specific to FPGAs.
 \section{Proposed solution}
 \label{sec:solus}
 
-Project Oscar aims to provide an hardware and software architecture to
-estimate and control the deflection of cantilevers. The hardware part
-consists in a high-speed camera, linked on an embedded board hosting
-FPGAs. By the way, the camera output stream can be pushed directly
-into the FPGA. The software part is mostly the VHDL code that
-deserializes the camera stream, extracts profile and computes the
-deflection. Before focusing on our work to implement the phase
-computation, we give some general informations about FPGAs and the
-board we use.
+Project Oscar aims  to provide a hardware and  software architecture to estimate
+and  control the  deflection of  cantilevers. The  hardware part  consists  in a
+high-speed camera,  linked on an embedded  board hosting FPGAs. By  the way, the
+camera output stream can be pushed  directly into the FPGA. The software part is
+mostly the VHDL  code that deserializes the camera  stream, extracts profile and
+computes  the deflection. Before  focusing on  our work  to implement  the phase
+computation, we give some general information about FPGAs and the board we use.
 
 \subsection{FPGAs}
 
-A field-programmable gate  array (FPGA) is an integrated  circuit designed to be
-configured by  the customer.  A hardware  description language (HDL)  is used to
-configure a  FPGA. FGPAs are  composed of programmable logic  components, called
-logic blocks.  These blocks can be  configured to perform simple (AND, XOR, ...)
-or  complex  combinational  functions.    Logic  blocks  are  interconnected  by
-reconfigurable  links. Modern  FPGAs  contains memory  elements and  multipliers
-which enables to simplify the design and increase the speed. As the most complex
-operation operation on FGPAs is the  multiplier, design of FGPAs should not used
-complex operations. For example, a divider  is not an available operation and it
-should be programmed using simple components.
-
+A field-programmable gate array (FPGA) is an integrated circuit
+designed to be configured by the customer. FGPAs are composed of
+programmable logic components, called configurable logic blocks
+(CLB). These blocks mainly contains look-up tables (LUT), flip/flops
+(F/F) and latches, organized in one or more slices connected
+together. Each CLB can be configured to perform simple (AND, XOR, ...)
+or complex combinational functions. They are interconnected by
+reconfigurable links. Modern FPGAs contain memory elements and
+multipliers which enable to simplify the design and to increase the
+performance. Nevertheless, all other complex operations, like
+division, trigonometric functions, $\ldots$ are not available and must
+be done by configuring a set of CLBs.
+
+Since this configuration is not obvious at all, it can be done via a
+framework that synthetize a design written in an hardware description
+language (HDL), and after, that place and route 
+
+ is used to configure a FPGA.
 FGPAs programming  is very different  from classic processors  programming. When
-logic block are programmed and linked  to performed an operation, they cannot be
-reused anymore.  FPGA  are cadenced more slowly than classic  processors but they can
-performed pipelined as  well as parallel operations. A  pipeline provides a way
-manipulate data quickly  since at each clock top to handle  a new data. However,
-using  a  pipeline  consomes more  logics  and  components  since they  are  not
-reusable,  nevertheless it  is probably  the most  efficient technique  on FPGA.
-Parallel  operations   can  be  used   in  order  to  manipulate   several  data
+logic blocks are  programmed and linked to perform an  operation, they cannot be
+reused anymore.  FPGAs are cadenced more slowly than classic processors but they
+can perform pipeline  as well as parallel operations. A  pipeline provides a way
+to  manipulate  data  quickly  since  at   each  clock  top  it  handles  a  new
+data. However, using  a pipeline consumes more logics  and components since they
+are not  reusable. Nevertheless it is  probably the most  efficient technique on
+FPGA.   Parallel operations  can be  used in  order to  manipulate  several data
 simultaneously. When  it is  possible, using  a pipeline is  a good  solution to
 manipulate  new  data  at  each  clock  top  and  using  parallelism  to  handle
-simultaneously several data streams.
+simultaneously several pipelines in order to handle multiple data streams.
 
 %% parler du VHDL, synthÃ¨se et bitstream
 \subsection{The board}
@@ -597,7 +604,7 @@ largely beyond the worst experimental ones.
 
 \begin{figure}[ht]
 \begin{center}
-  \includegraphics[width=9cm]{intens-noise20-spl}
+  \includegraphics[width=9cm]{intens-noise20}
 \end{center}
 \caption{Sample of worst profile for N=10}
 \label{fig:noise20}
@@ -605,7 +612,7 @@ largely beyond the worst experimental ones.
 
 \begin{figure}[ht]
 \begin{center}
-  \includegraphics[width=9cm]{intens-noise60-lsq}
+  \includegraphics[width=9cm]{intens-noise60}
 \end{center}
 \caption{Sample of worst profile for N=30}
 \label{fig:noise60}
@@ -618,7 +625,7 @@ SPL on $N = k\times M$, i.e. the number of interpolated points.
 
 We assume that $M=20$, $nb_s=1024$, $k=4$, all possible parts are
 already in lookup tables and a limited set of operations (+, -, *, /,
-<, >) is taken account. Translating the two algorithms in C code, we
+$<$, $>$) is taken account. Translating the two algorithms in C code, we
 obtain about 430 operations for LSQ and 1550 (plus few tenth for
 $atan$) for SPL. This result is largely in favor of LSQ. Nevertheless,
 considering the total number of operations is not really pertinent for
