Towards a Platform for Widespread Embedded Intelligence - ERCIM

iments. We tested and evaluated several
development boards for different
FPGAs. However, the flexibility of
reconfiguration was a limitation on most
of them. In the end we chose a very
simple and available FPGA board, the
so-called 'Suzaku system', which was
small and allowed us the flexibility of
reconfiguration that we required. This
system is really a Single Board
Computer in an FPGA with an external
flash memory for reconfiguration data
and some communication controllers for
LAN and serial line I/O.
We are now at version 1.0 of our project
roadmap. This is the first major version
where the tags are independent of any
development PCs or external computers.
The tag is now completely embedded on
the Suzaku board where the Xilinx
Spartan FPGA is configured with a
Microblaze CPU and devices for running
a Linux operating system variant.
Additionally, the tags are independent in
the sense that they can reconfigure themselves.
A simple web server is running
on the tag and, through a specific interface,
clients may download new configurations
for the FPGA, then the tag will
reconfigure itself and come alive again
with the basic CPU + Linux configuration
plus the newly configured hardware
architecture and the interconnections
between these sub-systems. The web
server interface enables a client to down-
Media streaming execution.
System-Level Design
of Fault-Tolerant Embedded Systems
by Alain Girault
load new configurations either directly
from itself or from any networked server
holding properly defined system configurations.
In order to test version 1.0 of the
AHEAD tag, we are currently developing
a demonstrator for MPEG recoding
and re-scaling. The objective is to
configure the tag for receiving massively
encoded media streams such as the
MPEG4 format and to decode the
stream, downscale it for a small screen
low-resolution viewer such as a PDA or
a Smartphone and recode the stream in a
more easily decoded MPEG format (see
illustration). MPEG4-streams are of
course well suited to limited bandwidth
Fault-tolerance is the ability of a system to maintain its functionality, even in the
presence of faults. With the advent of ubiquitous computing and distributed
embedded systems, it is becoming an aspect more and more crucial. We have
provided new functionalities to the SynDEx system-level CAD software. SynDEx
is ideal for optimising distributed real-time embedded systems and our new
functionalities allow us to guarantee a specified fault-tolerance level for the
generated embeddable code.
Our contribution to research in the faulttolerant
embedded systems consists of
several scheduling/distribution heuristics.
Their common feature is to take as
an input two graphs: a data-flow graph
ALG describing the algorithm of the
application and a graph ARC describing
the target distributed architecture (see
figure).
SPECIAL THEME: Embedded Intelligence
distribution over the net, but the complexity
of decoding them is too
demanding for low performance and
limited power devices such as PDAs and
Smartphones. The tag recodes the stream
for less performance and power in
decoding, but the format will demand a
higher bandwidth. This demand, however,
is not a problem since the tag and
the client are very close and higher bandwidths
are possible even with low
power. We expect to test this tag-based
recoder version of AHEAD by the end of
this year.
Please contact:
Kjetil Svarstad, NTNU, Norway
E-mail: kjetil.svarstad@iet.ntnu.no
Also shown is a table giving the worstcase
execution time of each operation
onto each processor and the worst-case
transmission time of each data-dependence
onto each communication link.
The architecture being a priori heterogeneous,
these need not be identical. Below
is an example of such a table for the
operations of ALG. The infinity sign
expresses the fact that the operation I
cannot be executed by the processor P3,
for instance, to account for the requirement
of certain dedicated hardware.
ERCIM News No. 67, October 2006 25