Re: Development of a distributed system based on firewire- advice needed...

On 31 Jan., 20:07, "Paul E. Bennett" <p...@xxxxxxxxxxxxxxxxxx> wrote:
maxpowe...@xxxxxxx wrote:
Hello,

I am comparatively new to the embedded world and hope to find here
some advices and inspirations and maybe answers to the many questions
I have.

Welcome to our world.

I am going to develop a distributed application with the following
characteristics. A central control programme (probably on a PC) shall
talk with a number of embedded devices (microcontroller with sensors
and actuators etc.) and the transfer rate shall be relatively high (in
fact there are real time issues). Also, the embedded devices shall be
hot pluggable meaning that the central control should become
immediately aware of a new deviced being plugged into the system.
Also, direct communication between the devices shall be possible which
suggests a multi-master-bus-protocol.

At first, I had the idea of developing all this Ethernet TCP/IP based
and develop all the hot-plug logic on my own. Unfortunately, TCP/IP is
too slow and I found that actually firewire is fast enough, cheap
enough, it's multi-master and it already has hot pluggability built
in!!! (Am I right??)

Not dealt with firewire but why does your analysis of the system
requirements suggest that you could not meet the real-time requirements
with a fast ethernet based system. There are some extensions to the TCP/IP
and ethernet protocols that address providing communication of data in
real-time across the network (sometimes by reserving specific time-slots
within the communications for specific purposes). See IEEE1588, TTP and
SafeNet for further information.

1.) Do you think, firewire is a good choice for my type of
application?? (it is an industrial one)

Don't know at this stage without some more specific details.

You say this is an industrial application and have hinted that there will be
sensors and actuators associated with each of the nodes. I would hope you
have done some work to establish what your system safety requirements are.
If not, you may have to consider wider measures than just whether or not
you are using Firewire, Ethernet of some other communications medium.

--
********************************************************************
Paul E. Bennett ....................<email:/...@xxxxxxxxxxxxxxxxxx>
Forth based HIDECS Consultancy .....<http://www.amleth.demon.co.uk/>
Mob: +44 (0)7811-639972
Tel: +44 (0)1235-811095
Going Forth Safely ..... EBA.www.electric-boat-association.org.uk..
********************************************************************

Hello,

thanks for your reply.....so, far the project is still in an early
stage with a lot of (unsure) assumptions concerning safety, speed etc.

The main reason why firewire came into my mind, is the "hot pluggable"-
feature the network shall provide (whatever bus or protocol is used).
This means, whenever a device is plugged into the system, the control
system shall become automatically aware of it.....I hope that I can
get this feature "free of charge" when i use firewire as a lot of very
clever people have developed it within 10years......and secondly, from
what I read it is very fast and safe.....

Concerning ethernet....I have so far only dealt with programming TCP/
IP and UDP/IP-applications, but because all the communication is
implemented in software, it takes quite a long time to transmit
packets, if i am not mistaken....I mean, when you use TCP/IP you have
to open sockets, bind to it, send data to the socket and so on.....you
are not directly using the (fast enough) ethernet protocol......To be
honest, I have no idea how i could develop an application that
communicates over pure ethernet, not TCP/IP over Ethernet.....I would
like to know that by the way, so if you have an advice here...

Thanks anyway...

.

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