> On Sat, 17 Jul 2004 12:32:18 -0700, DM McGowan II wrote:
>
>
>>http://www-ccs.cs.umass.edu/~shri/iPic.html
>
>
>
> 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.
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
"zalzon" <zalzonishappy@zalll.com> wrote in message
news:v0lhf051arjtgu6lstocj60rhhbtu7hrtb@4ax.com...
> 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...
On Sat, 17 Jul 2004 07:34:41 GMT, zalzon <zalzonishappy@zalll.com>
wrote:
>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...
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
Reply by Tsvetan Usunov●July 18, 20042004-07-18
zalzon <zalzonishappy@zalll.com> wrote in message news:<pan.2004.07.18.06.06.20.341246@zalll.com>...
> On Sat, 17 Jul 2004 12:32:18 -0700, DM McGowan II wrote:
>
> > http://www-ccs.cs.umass.edu/~shri/iPic.html
>
>
> 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.
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.
Reply by zalzon●July 18, 20042004-07-18
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.
Reply by Brian Murtha●July 17, 20042004-07-17
zalzon <zalzonishappy@zalll.com> wrote in message news:<v0lhf051arjtgu6lstocj60rhhbtu7hrtb@4ax.com>...
> 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.
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:8147http://www.rabbitsemiconductor.comhttp://www.zworld.comhttp://www.imaginetools.com
Reply by DM McGowan II●July 17, 20042004-07-17
"zalzon" <zalzonishappy@zalll.com> wrote in message
news:v0lhf051arjtgu6lstocj60rhhbtu7hrtb@4ax.com...
> 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...
"Markus Zingg" <m.zingg@nct.ch> wrote in message
news:abthf0posrae1bj441r2pfdssucpc3p1kl@4ax.com...
> >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...
>
> 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.