Hi,
It's a calibration system, and as such it requires high reliability.
Networking and addressing leaves the system open to problems such as
if one RS485 chip goes short circuit, for example, it will bring the whole
network down and screw up the (lengthy) calibration process
Therefore IT MUST be designed this way, unless you can think of anything
better
Separating each channel isolates unit specific problems to just that channel
-----Original Message-----
Declan Moriarty
Sent: 23 August 2005 17:49
To: Multiple recipients of list CHIPDIR-L
Recently, Somebody Somewhere wrote these words
> Hi,
>
> Thanks.
>
> I think I should have been more specific.
>
> We've got an RS485 comms pair, which we want to multiplex between 120
> RS485 pairs.
>
> I.e. 120 channels to 1 (or 240 to 2 in terms of actual wires).
>
> Ive seen a 32 channel analogue switch from Analogue devices, but im
> unsure as to whether an Analogue switch will be ok?
>
To quote the Irishman who was asked for directions to somewhere:
"You know... If I was you, I wouldn't start from here at all!"
You are never going to stand up 1-->120 in an RS485 link without such
heartache as to justify a sane design. What's your baud rate? You would
also need sample & holds everywhere. Network the things and address
them. Start over, my friend.
Imagine when you get the complaint "Channel 87 goes intermittent after
about 5 minutes" How will you sort that?
BTW, the trick with analogue switches is never bring the input below the
negative rail.
--
With best Regards,
Declan Moriarty.
--
Author: Declan Moriarty
INET: [EMAIL PROTECTED]
Fat City Hosting, San Diego, California -- http://www.fatcity.com
---------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB CHIPDIR-L
(or the name of mailing list you want to be removed from). You may
also send the HELP command for other information (like subscribing).
--
Author: Darren Logan
INET: [EMAIL PROTECTED]
Fat City Hosting, San Diego, California -- http://www.fatcity.com
---------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB CHIPDIR-L
(or the name of mailing list you want to be removed from). You may
also send the HELP command for other information (like subscribing).
