On Tue, 4 Sep 2001, Byron A Jeff wrote:

> 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.

Couldn't agree more.

> 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.

Again, agreed.  Actually, I can think of uses for an HTTP interface to a
PIC, but I think a lot could be done without it.

> 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.

UDP definitely is a lot simpler to implement.  Once you have IP/UDP sorted
out, you have the use of DNS, SNMP, and other very useful protocols.  The
only real down side is that most firewalls will summarily deny UDP, so
it's commercial applications are a little limited for some products.

> 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.

Here's where I have a problem with most existing stacks.  SLIP is OK for
something that will be connected to a dedicated box - like directly wired
to a Linux machine's serial port, for example.  But for applications that
will need Internet dialup connectivity, PPP is pretty much a requirement I
would think.  Actually I'd be much happier with Ethernet, but there you
have a requirement for either an ISA bus card (endangered species) or lots
of surface mount and some magnetics.  I have a couple of stalled projects
because I just haven't found a really good solution for this issue - but
then I work with a peculiar set of restrictions, so this is not a problem
for a lot of people.

I've also spent a lot of time writing a "bulletproof" modem dialer, one
that will be able to handle redials, busies, no-answers, modem hangs, etc.
It's NOT pretty and takes an awful lot of code space as it is.  One of
these days I need to rip it completely apart and start from scratch.

Dale
---
Hallo, this is Linus Torvalds and I pronounce Linux as Leennuks.
Hallo, this is Bill Gates and I pronounce 'crap' as 'Windows'.

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