I use 485 pretty extensivly.  I have switched form the standard 75176 to a
SN65LBC184 which only counts as 1/2 a load and has some pretty good built in
static discharge protection.

-----Original Message-----
From: Simon Bryden [mailto:sbryden@FREE.FR]
Sent: Friday, August 16, 2002 6:34 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [PIC]: CAN or RS-485 ?


One issue here is that RS485 only defines an electrical spec; it does not
define the data format or even character framing - you have to do this
yourself. CAN on the other hand defines all of this and more and is
extremely
complex. If you use CAN, you pretty much need to implemnt it in hardware
which
will impact the cost. RS485 is cheaper but you will have a bit more work to
do.

I've never used the MAX485 but can highly recommend the 75176.

Cheers,
Simon.
---

On Fri, Aug 16, 2002 at 12:56:46PM -0700, Nelson Hochberg wrote:
> I am planning a system with a network of PICs.  The PICs will be daisy
> chained together (power and communications) in a standard office
environment
> (fluorescent lights, networked PCs, telephones, HVAC, etc.)  The PICs will
> need to communicate about two bytes (status change of nine LEDs and which
> PIC sent the event) every 5-10 minutes.  Two of the events are pretty
> important and would need to be acknowledged by the other PICs.  Initially,
> the network will be 300' end to end with 18 PICs.  The network could
expand
> to 2000' end to end and about 100-200 PICs.
>
> I've got it whittled down to either a CAN or RS-485 (unless someone can
> convince me another protocol would be better.)  Which one do you think is
> better and why.
>
> If I use 18F248/448 do I need to use a transceiver interface such as
> PCA82C250 or can the PICs connect to the wires directly?  Any
> recommendations for an interface?
>
> I was thinking of using the MAXX485 if I went with RS-485.  Any other
> suggestions?
>
> TIA
>
> Nelson
> nelson@nosuffering.com
> www.nosuffering.com
>
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