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wireless comms/networking

Discussion in 'General Electronics' started by Jeffrey Dutky, Aug 19, 2004.

  1. I'm an amatuer electronics hacker (a couple of college courses and a
    bunch of reading) and I'm interested in fooling around with wireless
    networking stuff. I've surfed the web for 802.11 related chips but am
    finding my lack of experience a problem: I just don't understand most
    of the jargon or acronyms and I'm not too clear on how the different
    parts fit into the overall system. I need a good primer on something,
    but I don't even know enough to name the subject.

    Almost everything I've seen is clearly operating in the
    analog/radio-frequency domain, with which I have almost no experience.
    I've seen ONE product that appears to provide a CPU bus interface on
    one end and antenna connections on the other, everything else lived
    somewhere inbetween (closer to the antenna than the CPU bus), so I
    need something that covers that subject matter.

    Any advice would be appreciated.

    - Jeff Dutky
     
  2. What do you want to *do*?
     
  3. First, I'm trying to add WiFi to an ARM based device I'm building.
    Currently I have a WiFi Compact Flash card, but I'd like to free up
    the CF slot.

    Second, I'm just curious and willing to learn. There is clearly a
    bunch of domain specific stuff I don't understand. I'd rather learn to
    fish than keep buying fish fillets.

    All I need is either a pointer to a good book (or two) or some of the
    appropriate terminology so I can do a useful web search.

    - Jeff Dutky
     
  4. Wi-Fi is way overkill for a beginner. You'll end up spending more
    time configuring than actually understanding.

    Your best bet is to make your own transceiver using the basic analog
    techniques you have learned so far. A Colpitts oscillator and a few
    OP-amp circuits will go a long way. Focus on being able to get a
    simple mark or space over your bi-directional virtual wire from one PC
    to the other, and attach this wire to the trasmit/receive pins of the
    UARTs, making sure to set the baud rate at lowest level available.
    You can use basic tools like HyperTerminal to see if it is working.
    It will also be fun to add whatever LED indicators to your circuit you
    need to show transmit and receive, etc.

    Once you are able to get a byte from one end to the other somewhat
    reliably, everything else will follow, as you can program any
    higher-level functionality (like framing and error correction) using
    the serial communications functions.

    The speed and range won't be as good as Wi-Fi, but such a project
    would prepare you for the higher-level jargon.

    -Chaud Lapin-
     
  5. If your card has an USB port, you could use an USB WiFi adapter - or you
    could get/use an PCMCIA port.

    My problem in answering is because I do not know if is an this is something
    you are playing with for "hack value" or you are trying to build some
    product to sell. If it is for self, I would choose to hack a commercial
    product .. see below,.
    The trouble is that the volume of what one has to learn in order to *build*
    something like a WiFi device with the associated protocol stack is so large
    that one will spend maybe a year figuring out what to do and how to do it -
    in the meantime the standards will have changed and the hardware device you
    wanted to use are entering the "Last Buy" zone!

    Therefore the Lego Design Principle (tm): *Buy*/Download the stuff, slap it
    together and get the *Application* you wanted to *use it for* going on some
    generic hardware; If there is a volume market in it one can re-engineer it
    into a product rather faster than by designing from scratch.

    Look at LinkSys WRT54G f.ex.: There is a vanilla Intel IXP425 Development
    board in that with a Broadcomm WiFi Device on it, running an Embedded
    Linux - the source and toolchain is available from LinkSys too - all for
    less than USD 100.

    The Linksys NSLU2 network storage device follow the same formula:
    Concentrate on The Job, Source in the Components (soft and hard) and add the
    Icing that make the Ready-Made Cake Mix into Your Product.
    The above devices are hackable - and there are tools on the net too:
    http://www.linuxdevices.com/news/NS5922195910.html
     
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