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Ethernet

Discussion in 'Microcontrollers, Programming and IoT' started by coffeecuppepsi, Apr 4, 2010.

  1. coffeecuppepsi

    coffeecuppepsi

    9
    0
    Apr 4, 2010
    Hi!

    I have experience with PIC and protocols, however I can't get my head around ethernet.. What i want to do i make an embedded server to monitor inputs in my house, i may then log into the Server via my fone and view inputs, set outputs, etc...
    I know there are hundreds of suck projects on the net, however all the ones i found use premade libraries etc... i don't just want to put someone else's code into my PIC and not know what it does!! i really want to UNDERSTAND what sort of protocols and commands my pic needs to respond to in order to do this....

    PLEASE if anyone out there can suggest some reading material for me i'll appreciate it..
    regards
    ryan
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,192
    2,694
    Jan 21, 2010
    Why not look at microchip's open source implementation of the TCP/IP stack. ALternatively, there is an old sourceforge project that involved interfacing an ISA network card to a PIC.

    Here is a very old project that describes the process in overview.

    Here is a (1980) spec for ethernet. Wikipedia provides a useful gateway to the TCP/IP specs. (Wikipedia's entry for 802.3 similarly provides lots of information -- and pointers to source documentation -- for ethernet, but are you *really* going to be implementing the hardware level?)
     
  3. coffeecuppepsi

    coffeecuppepsi

    9
    0
    Apr 4, 2010
    thanks for the info. nah i don't need to do hardware, as the pic18f i've chosen has the hardware, i just need to add the rj45 plug :)
    what i don't want is to simply use the tcp/ip stack without knowing how much of it i'm really using and how it works...
    i'd like to write my own stack, with the minimal code needed to do what i need it to do
     
  4. coffeecuppepsi

    coffeecuppepsi

    9
    0
    Apr 4, 2010
    ethernet socket

    Hi guys!
    most circuit diagrams use an ethernet socket with internal magnetics... the example in mikroElectronica however does not mention this, it just shows a socket with a few resistors and one inductor.... does this work? i suppose the magnetics makes a better system, but the second option should be good enough to just hook up to my hub for testing at home?

    cheers
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,192
    2,694
    Jan 21, 2010
    Perhaps a link or two would help us help you...
     
  6. coffeecuppepsi

    coffeecuppepsi

    9
    0
    Apr 4, 2010
    Fair enough !

    here's the mikroelectronica example..
    http://www.unitone.com.br/arquivos/mikroeSch.jpg

    there's no mention of magnetics... also pins 1 to 8 differ with the second schematic.. which is this one...
    http://www.tehhouse.us/book/that/wp-content/uploads/2010/01/enc28j60_app.png

    as you can see, on the socket, pins 4 and 5 are shorted in the second diagram but not mentioned in the first... most anoying are pins 7 and 8 on the second diagram shorted together... but these are signal pins on the 28j60 on the first diagram...

    can anyone explain this to me please??

    cheers
     
  7. 55pilot

    55pilot

    434
    3
    Feb 23, 2010
    The first diagram has the magnetic built into the connector. The rest of the confusion is about semantics of documentation.

    Ethernet requires a transformer. There is no getting around that. Some RJ connectors are made with transformers in them. Some PHYs are made with transformers in them as well. Because you do not see a transformer explicitly listed in the schematic does not mean it is not there.

    ---55p
     
    Last edited: Apr 20, 2010
  8. coffeecuppepsi

    coffeecuppepsi

    9
    0
    Apr 4, 2010
    Thanks! I went out and bought the correct socket (with magnetics).
    Now another question. I HAVE read the documentation, but there's still something i'm not getting, the TCP/IP stack from microchip.. if i use a 28J60 ethernet controller then some opperations would be handled by the chip itself, so i don't need the entire TCP/IP stack? or do i?.. where can i draw the line at what the chip does and at what the stack does?
     
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