On Wed, Jun 23, 2004 at 01:44:11AM +1000, Trungie*! wrote:
> I have a PIC device that connects to my PC via serial port for constant
> communication.

OK.

>
> I would like to have over 10 PIC devices connected to my PC somehow for
> communication.

Well that's a challenge. A couple of questions:

1) Do all of the PICs have to be able to communicate at the same time?
2) Is the communcations required going to have to be bidirectional?

> However, i would not like to buy some sort of expensive multi serial port
> card for it.

That could be painful.

>
> What sorts of things can i do to over come this problem? Potentially i would
> like to use over 10 of these PIC devices at once.

Well it gets back to the questions above. If each and every PIC needs to be
able to independently communicate at the same time, then you're pretty much
stuck with having a serial port per PIC and the multi-serial solution.

However if you can arrange so that the PC can pick which PIC to talk to, then
you can arrange what is known as a multidrop network where all of the PICs
share the same serial connection.

The most popular hardware interface for multidrop serial is EIA485 (also known
as RS485). It's cheap and reliable. However there's no specified protocol that
sits on top of it to talk to each of the individual PIC nodes. So you'll have
to fish around for ways of doing it.

Hope this gets you started on the subject.

BAJ

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