Embedded webserver on an 8 bit MCU

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Back from the grave.

To advance my knowledge of embedded systems, I would like to build an
embedded webserver on an 877 PIC microcontroller.  Nothing fancy as
far as the webserver is concerned.  

From what I gather, i need to impliment a tcp/ip stack on the MCU and
somehow hook it up to an ethernet card.  For now, I've focused my
efforts at learning TCP/IP in as much detail as I can.

Have any of you guys done such a project and if so what advice can u
give me.  I'm just trying to learn so go easy on the abuse...  

Re: Embedded webserver on an 8 bit MCU

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Take a look at the following link:

http://www.ethernut.de

I think the Atmel AVR is a much better choice than PIC 16 series for
any application that requires the use of C language.

regards,
Johnny.


Re: Embedded webserver on an 8 bit MCU
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Apart from the good link to ethernut which the other poster provided,
there are many such projects around. In particular I can recommend you
the Book from Jeremy Bentham "TCP/IP lean" which contains a PIC
Webserver example and all TCP/IP related information source code etc.

The best piece of information to get me started was the slaa137.pdf /
slaa137.zip technote from TI which describes how to implement the very
subject on one of their MPU's. I found the TCP/IP stack there
(including all source) a very good starting point in that it really
focuses on the "bare bones" of the topic. It's therefore easyier to
understand. Reading the related RFC's (start with RFC 793) will also
help a great deal. Understanding the TCP state engine - while not
rocket sience - is not that easy at the first glance. You therefore
may have to use multiple sources.

If you want to go the easy route or find it too dificult to implement
all by yourself you may also want to take a look at what Rabbit
Semiconductor offers ( www.rabbitsemiconductor.com ). There you can
get Core Modules all ready including a complete developement
envireonement with a TCP/IP stack, Webserver code etc. etc. Another
probably similar aproach is the EZ80 stuff from Zillog. They don't
work with PIC's though.

If you intend to do more stuff with your developement except for
switching two or three things on and off through the webserver, you
probably should consider using something other than a PIC. In other
words - it's doable with the PIC, but apart from the webserving there
are probably not much resources left to do other things.

HTH

Markus


Re: Embedded webserver on an 8 bit MCU
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Olimex sells a ready-made version of the above:

http://www.olimex.com/dev/msp-easyweb2.html

Leon



Re: Embedded webserver on an 8 bit MCU
Thanks guys but I should have added to my original message that I intend
to stick with the PIC.  I know there are other microcontrollers out there
which might be better suited for this task.  My objective however is to
learn more about TCP/IP and struggle through it.

My idea for this project was fired when I heard a couple years back of a
guy who built the smallest webserver by using the smallest 8051 chip he
could get his hands on.  I figured if he could do it on such a small chip,
I should be able to do it on a much larger 40 pin PIC 877.

I'll check out the resources you recommended for learning this.  Right now
I'm studying the basics of TCP/IP.

Re: Embedded webserver on an 8 bit MCU
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http://www-ccs.cs.umass.edu/~shri/iPic.html


Re: Embedded webserver on an 8 bit MCU

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That's exactly what I had in mind except I plan not to use an external
EEPROM to store webserver files.  In fact I remember visiting the guy's
iPIC server when he first got it up.  It attracted so many visitors
that the little iPIC crashed.  He had to take it offline and set up a
simulated version of it on a webpage.  I remember reading the text file
'History of the World' on his iPIC though. :)

Now if only he had provided the TCP/IP code and explained it.  He
claims the TCP/IP code fits in just 256 bytes with the EEPROM chip
holding the server's files.  Pretty impressive little gizmo.





  

Re: Embedded webserver on an 8 bit MCU
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Actually you can find on the net the sources of Russian guy who did
the same.
There is mirror of his page at PICLIST:
http://piclist.com/techref/piclist/petrovwwwpic/index.htm

Note that this is hard to say TCP/IP stack. It handles very limited
features of TCP/IP and allow only single connection.

Best regards
Tsvetan
---
PCB prototypes for $26 at http://run.to/pcb
(http://www.olimex.com/pcb )
We've slightly trimmed the long signature. Click to see the full one.
Re: Embedded webserver on an 8 bit MCU
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It's clever, but it's not what the author claims it to be.  Here's the
rough algorithm for how it probably works:

1.  receive header of IP frame (via SLIP)
2.  swap destination and source addresses (and ports)
3.  send the modified header in reply
4.  use the destination port number as EEPROM address
5.  send the data found at that address, byte at a time

It gives somewhat the appearance of a real TCP/IP stack, but it
certainly *not* RFC-1122 compliant as the author falsely claims.  For
instance:

       3.3.2  Reassembly

          The IP layer MUST implement reassembly of IP datagrams.

          We designate the largest datagram size that can be reassembled
          by EMTU_R ("Effective MTU to receive"); this is sometimes
          called the "reassembly buffer size".  EMTU_R MUST be greater
          than or equal to 576, SHOULD be either configurable or
          indefinite, and SHOULD be greater than or equal to the MTU of
          the connected network(s).

Obviously, this implementation (and all similar ones) cannot support
reassembly because they simply don't have enough memory to store a full
frame (which MUST be greater than or equal to 576 bytes).  Such
implementations are interesting but they are not real TCP/IP stacks any
more than a toothpick is a grand piano.

Ed


Re: Embedded webserver on an 8 bit MCU
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I don't think you'll be able to implement a robust TCP/IP stack and
HTTP server on that microcontroller without external RAM and probably
external flash.

Rabbit Semiconductor has complete development kits for
Ethernet-enabled core modules starting under $200. A full version of
the compiler and TCP/IP stack with source code is included with all
dev kits. You won't get to implement your own stack (a very
non-trivial task), but you can still learn a lot.

Here is a live web server demo running on a core module:

  http://demo.zweng.com:8147


http://www.rabbitsemiconductor.com
http://www.zworld.com
http://www.imaginetools.com

Re: Embedded webserver on an 8 bit MCU

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You may also want to look at the Wiznet chip. This is a chip that runs
a TCP/IP stack which you can access as am 8 bit peripheral or via an
I2C Bus. It can handle up to 4 simultaneous links, which should be
fine for any sort of web based user interface.
With the W3100A you need in the order of 10 instruction lines to be
able to ping your device.

Regards
   Anton Erasmus


Re: Embedded webserver on an 8 bit MCU

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Have a look at www.edtp.com

http://www-ccs.cs.umass.edu/~shri/iPic.html
http://www.edcheung.com/awards/pic2k/code.htm
http://members.vol.at/home.floery/electronix/picnic/webserver.html
http://www.kyllikki.org/hardware/wwwpic2 /
http://www.olimex.com/dev/picprojects.html
http://web51.hw-server.com/links.html
http://www.commlinx.com.au/microcontroller.htm

Alex



Re: Embedded webserver on an 8 bit MCU


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Thanks Alex, that should prove helpful.

  

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