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Thread: Embedded Internet enabling methods: Which?
www.piclist.com/techref/index.htm?key=which
face picon face BY : Byron A Jeff email (remove spam text)



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You're right on the mark here Bill. The bottom line is that microcontrollers
aren't really designed for that level of networking. And aside from the
"coolness" factor and compatibility with existing protocols, designing
a full TCP/IP implementation for a microcontroller doesn't buy you very much.

All of your typical heavyweight net applications take advantage of the fact
that the underlaying OS implements the full TCP stack. But TCP as a protocol
puts really heavy demands on the OS. Buffering, retransmissions, flow and
congestion control, and the like cost in code size, data memory required, and
computational complexity.

As I've said before in this forum that UDP/IP is the savior for ucontrollers
requiring internetwork capability because the loss of reliable, sequential
flow controlled delivery completely simplifies the stack implementation. The
only minor cost is having to write an application at the client end to
interact with PIC. But the client doesn't have to be a gateway, it can be
located anywhere on the internet.

The bottom line is that applications are way too varied and ucontroller
way to limited to afford sticking a "standard" OS on them. OTOH a UDP/IP
library could have some utility. Let's see how it stacks up against the
original issues:

"... API library ... standard calls:" This isn't a bad idea. A library with
open, send, receive, and close calls for UDP could be useful.

"certain ports:" The API could easily be designed to handle multiple/varied
ports. And a library implementation would have to. It's just easier to
hardcode a port number...

"[only] ppp/slip link:" This is a matter of the hardware. Ethernet is
easily achievabile with chips like the CS8900. Other's have looked at
RealTek chips and NE2000 interfaces. But the hardware implementations for
PPP/SLIP are much more cost/space effective. A standalone serial link can
be built using a single 8 pin DS1275 or a MAX232 whereas the ethernet
implementations requires a bunch of pins.

Just some thoughts.

BAJ

<200005301430.KAA17022@bikini.cc.gatech.edu> 7bit

In reply to: <CMM.0.90.4.959670198.billw@flipper> from "William Chops Westfield" at May 30, 2000 12:03:18 AM
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