Multi-drop network

Heinz-J=FCrgen Oertel wrote:

> Don't like to offend, but did you make your calculations on the best use =
of
> CAN?

Yes. Its an absolute requrement that we be able to transfer 2MByte of
data in under a second.=20

TW

Grant Edwards wrote:

> How about 10base2 Ethernet?

Grant

We are currently using 10Base 2. It is pretty much an obsolete
technology these days. Most of the major manufacturers have obsoleted
their PHYs for it. Designing it into a product that will have a life of
5+ years doesn't seem like a safe decision right now.

Cheers
TW

On Monday, in article
     <GZmdnXf_jYktYPLenZ2dnUVZ_sOdnZ2d@forethought.net>
     donald@dontdoithere.com "Donald" wrote:

>Grant Edwards wrote:
>>>3. Transfer rate > 3MBytes/s = 30Mbits/S
>> How about 10base2 Ethernet?  = 1Mbytes/S
>
>Dosen't cut it.

Considering ISA is classed as a 2MBytes/sec bus (as PC104 = ISA), how are
you going to get 3MBytes/sec across?

Personally at these rates either use as someone else has said PC104plus for
higher bandwidth.

Then consider 100baseT network and accept the uncertainty factor, or split
your 20 nodes into sub-networks of smaller sizes each with its own 'network'
interface. Your network interface then can be RS422/485, or other means.

Personally I think you are trying to "fit a quart into a pint pot".

-- 
Paul Carpenter          | paul@pcserviceselectronics.co.uk
<http://www.pcserviceselectronics.co.uk/>    PC Services
<http://www.gnuh8.org.uk/>              GNU H8 & mailing list info
<http://www.badweb.org.uk/>             For those web sites you hate

Ted wrote:
> I'm looking for a networking technology with the following requirements
> 
> 
> 1. Multidrop.No hub/router/switch
> 2. Up to 20 nodes
> 3. Transfer rate > 3MBytes/s
> 5. Supported by an off-the-shelf PC104 type card for an industrial PC
> (master)
> 5. Easy to implement in HW (slave)
> 
> 
> Anyone got any ideas? CANBus comes close, but isn't fast enough.

With simple selfmade hardware this specification is
doable. As physical medium choose RS422, RS485, LVDS,
all on twisted pair. A separate clock line allows
synchroneous hardware. As serializer/deserializer,
have a look at CPLDs & Serdes.

Rene
-- 
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net

"Ted" <ted.wood@sortex.com> wrote in message
news:1131361041.613821.185530@o13g2000cwo.googlegroups.com...
> I'm looking for a networking technology with the following requirements
>
>
> 1. Multidrop.No hub/router/switch
> 2. Up to 20 nodes
> 3. Transfer rate > 3MBytes/s
> 5. Supported by an off-the-shelf PC104 type card for an industrial PC
> (master)
> 5. Easy to implement in HW (slave)

Since you don't specify a bus width, have you considered SCSI?
Years ago I saw an article in DDJ where somewone had networked a couple of
PCs through SCSI.
I know the SCSI standard does not support more that 8/16 devices, but you
could use the SCSI hardware to implement your own protocol and thus address
more that 16 devices.

Meindert

Paul Carpenter wrote:


> Personally at these rates either use as someone else has said PC104plus for
> higher bandwidth.

No problem.

> Then consider 100baseT network and accept the uncertainty factor,

Its not a real time issue, its a "20 port switches for industrial
temperature ranges cost serious money" issue.

> Personally I think you are trying to "fit a quart into a pint pot".

I'm designing down to a price. If it can't be done I'll have to think
again.

TW

"Ted" <ted.wood@sortex.com> wrote in message
news:1131448317.622174.182400@g44g2000cwa.googlegroups.com...
> Its not a real time issue, its a "20 port switches for industrial
> temperature ranges cost serious money" issue.

And developing your own interface from scratch isn't?

Meindert

Meindert Sprang wrote:

> > Its not a real time issue, its a "20 port switches for industrial
> > temperature ranges cost serious money" issue.

> And developing your own interface from scratch isn't?

I've got no interest at all in developing an interface from
scratch.Thats why I'm asking here.
Although if it meant saving the cost of a 20 port Ethernet switch in
each machine I'd give it serious consideration.

TW

On Tue, 08 Nov 2005 11:31:42 +0100, Rene Tschaggelar <none@none.net>
wrote:

>Ted wrote:
>> I'm looking for a networking technology with the following requirements
>> 
>> 
>> 1. Multidrop.No hub/router/switch
>> 2. Up to 20 nodes
>> 3. Transfer rate > 3MBytes/s
>> 5. Supported by an off-the-shelf PC104 type card for an industrial PC
>> (master)
>> 5. Easy to implement in HW (slave)
>> 
>> 
>> Anyone got any ideas? CANBus comes close, but isn't fast enough.
>
>With simple selfmade hardware this specification is
>doable. As physical medium choose RS422, RS485, LVDS,
>all on twisted pair. A separate clock line allows
>synchroneous hardware. As serializer/deserializer,
>have a look at CPLDs & Serdes.
>

TI makes a number of serdes chips. 

Maybe IEEE 1399 is an option ? Upto 63 devices may be daisy chained
and the data rate is 400Mb/s.  Cable length between devices are only
upto 4.5m. It looks like one of the variants based on this core
technology should handle your requirements. 

Regards
  Anton Erasmus

Ted wrote:

> Paul Carpenter wrote:
> 
> 
> 
>>Personally at these rates either use as someone else has said PC104plus for
>>higher bandwidth.
> 
> 
> No problem.
> 
> 
>>Then consider 100baseT network and accept the uncertainty factor,
> 
> 
> Its not a real time issue, its a "20 port switches for industrial
> temperature ranges cost serious money" issue.

I recently got a 16port 10/100Mbit Switch at FRYs for 20$,
possibly not industrial temperature range.

Rene
-- 
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net