On Mon, Sep 03, 2001 at 10:14:51AM -0700, Richard wrote:
> Hello all,
>
> I'm looking for some assistance in working on a small PIC project, to keep me out of mischief
> while
> living in London for a few years.
>
> What I wish to create is a PIC TCP/IP based board, that has the ability to be controlled
> entirely by TCP/IP and perhaps rs232 for monitoring/test purposes.  It will control a few 12 volt
> items lets say turn on a led, or a little motor,   and also have the ability to turn on/off a 240v
> load.
>
> So basically the board can be controlled by a standard PC, via TCP/IP or RS232 and it will allow
> you to turn on and off a couple of relays for lights and motors, and also a 240 load on and off.
>
> I also do not believe in reinventing the wheel, so thought I'd put out some feelers to see what
> others have done,  maybe there are some do's and dont's also.  Which particular PIC chip would
> be
> the best to use for this kind of a device...  I'd prefer to use the most powerful PIC chip that I
> can ... powerful being the most universal for future enhancement etc.
>
> I guess I'm kind of looking for a partner to work with remotely, or together on coming up with
> a prototype and to further the ideas and main idea for the devices use.
>
> I have seen a lot of the PIC based web servers, which could possibly be the core TCP/IP and
> control system for the device.  This will be a fun project to get into if anyone is interested.
>

Well I'll throw in the same two cents I always do on the subject:

I believe the the core power of the Internet and the TCP/IP protocol is in
network routability. Once you get the power to transmit packets over multiple
networks, the vast majority of the power of the Internet becomes available.

So when it comes to small uC projects, I personally believe that IP is the
key enabling technology.

Almost everytime this subject comes up, the context of the PIC based webserver
get bandied about. While cute in concept, I believe that it's not the most
effective use of the PIC's resources. Much of the same functionality can be
achieved with simpler protocols.

I believe that the appropriate transport protocol is UDP. With its paper thin
wrapping over the core IP protocol, and its standard and widely deployed API
interface, it's perfect for a PIC to interact on the Internet.

I do realize that it will require a bit more effort from the client interfacing
to the project. But all that's really required is a bit of interface from
the user to UDP. This can be done in Java, Perl, or PHP fairly easily. Since
the client (or gateway server if you choose to go that route) has much more
resources, and well tested network stacks, it'll save a heap of work trying to
debug the networking on the PIC.

My students and I have been working on and off on a UDP/IP/SLIP stack with
a linux gateway interface. The interface box is simply to allow for SLIP to
be used. Since SLIP is basically a trivial wrapper over IP, it's real easy
to implement and test on the PIC.

The project has been slow/dormant for the last 9 months or so. I'm hoping that
a new batch of students will pick up the flag. The last significant work was
getting PING working. Extending to and UDP/IP stack shouldn't be that
difficult. Eventually testing with a RS485 multidrop network is on the list
of things to do.

As for hardware there are a couple of good ideas floating around out there:

1: parallel port network pods. Many have Linux drivers from which the protocol
can be gleaned.

2: ISA port cards. Same deal.

3: RTL8139 chips. Have a simple 8 bit mode with some limitations. Real cheap.

4: Serial. This is the option I'm pursuing for now.

Anyway I hope this gives you some things to think about.

BAJ

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