RE: Re: RS485 - XPL on the wire

["Ian Lowe" <ian@xxxxxxxxxxxxxxxxxx>]

One of the biggest gotcha's for me was simply the technical aspects of
RS485 on the wire...

One station can talk, the others listen - easy enough, but how can you
*tell* someone else is talking?
I guess I'm thinking in terms of a CSMA/CD situation like ethernet and
couldn't find any RS485 chip that gave you Carrier feedback to indicate
that the media was in use.

I guess you'd have to implement a token passing network system like
token ring...

Ian.

-----Original Message-----
From: Frank Mc Alinden [mailto:fmcalind@xxxxxxx]
Sent: 22 October 2004 08:07
To: ukha_xpl@xxxxxxx
Subject: Re: [ukha_xpl] Re: RS485 - XPL on the wire


Hi Lehane / Ian

Like Ian  I am also interested in xpl 485 enabling
stuff...But to develope stuff we need to get more feedback from xPL
Users on the sort of devices that they would like....Would be nice if
several rs485 developements going on at the same time by different
people.....I think there would need to be a RS232 / 485 convertor made
which means one side would have to be bit banged , not aware of any pics
with  2 uarts ??or a commercially available unit ?? .............Have
done a little bit on rs485 and used the chksum as you
decribed.............Im more than happy to get involved in
rs485 projects if  others are and there is enough interest as well......

This link mentions the rs485 stuuf i was playing with
http://skybax.rapidhoster.co.uk/~armagh/page10.html

Frank


----- Original Message -----
From: "g8kmh" <lehane@xxxxxxx>
To: <ukha_xpl@xxxxxxx>
Sent: Friday, October 22, 2004 1:49 AM
Subject: [ukha_xpl] Re: RS485 - XPL on the wire


>
>
> OK,
> I'd missed xpl_devcom in my searches, oops!
>
> LRC-8 is a simple checksum on the message. XOR everything after STX
> including ETX and the result is the checksum. No big deal to do and
> offers some protection against message corruption, which since the
> RS485 is going to be around mains cabling (even taking into account
> normal separations) I think is a reasonable precaution.
>
> Be interested in the PIC implementations....
>
> Thanks,
> Lehane
>
> <snipped>
>
>
>
>
>
>
> xPL Links: http://www.xplproject.org.uk http://www.xplhal.com
http://www.xpl.myby.co.uk
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