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'[ot]: wifi cameras'
2004\01\12@181036 by rad0

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Can anyone explain or provide a link to an explanation
how this works?

I know the various wifi devices become items on the
wireless network.

Is a device like this 'home brewable'?

The camera, for instance, comes with an application that
evidently communicates with the camera and displays the
picture in a little window.

Thanks

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2004\01\12@182117 by Josh Koffman

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Well, I think you need to define home brewable. Also, it depends on how
small and integrated you want it to be. You could always put a USB
webcam on a laptop, stick an 802.11 card in it and run some software.
However, if you want it all in a tiny little package, if becomes much
harder. Coding for 802.11 isn't trivial, even on a processor designed
for IP communications like the IP2000 series from Ubicom.

Josh
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completely foolproof is to underestimate the ingenuity of complete
fools.
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rad0 wrote:
> I know the various wifi devices become items on the
> wireless network.
>
> Is a device like this 'home brewable'?

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2004\01\12@192226 by M. Adam Davis

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I'd actually like more information about this, as I always considered
802.11 devices as simple packet devices - you give tham an ethernet
packet, and they deliver it to all the other 802.11 devices in range.  I
thought they took care of the physical layer completely.

Is there something more to 802.11 devices that I wouldn't have to deal
with on, say, an NE2000 ethernet card?

Thanks for the info!

-Adam

Josh Koffman wrote:

{Quote hidden}

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2004\01\12@192433 by Herbert Graf

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> Can anyone explain or provide a link to an explanation
> how this works?
>
> I know the various wifi devices become items on the
> wireless network.

       The devices I've seen basically have a web server embedded, to the network
the camera looks like any other Ethernet device, with a web server.

> Is a device like this 'home brewable'?

       Most definitely, easiest way is with an old computer an Linux. To keep it
similar in size to those on the market isn't trivial though.

> The camera, for instance, comes with an application that
> evidently communicates with the camera and displays the
> picture in a little window.

       Usually you open the connection with a web browser, the camera's server
uploads a Java applet that results in you seeing the video. Neat devices,
far to expensive at the moment for me, but prices will drop. TTYL

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2004\01\12@200701 by Liam O'Hagan

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You could perhaps implement such a device using something similar to the
Lantronix Xport that I'm in the process of buying...

http://www.lantronix.com

> {Original Message removed}

2004\01\12@220619 by Josh Koffman

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Hmm. Well, I remember a discussion a few years back, someone wanted to
use some 802.11 cards to run an intercom I believe. I think they
scrapped the idea when they realized that much of the work involved was
done in the software driver, not in the hardware, thus making embedded
work pretty hard. I'm guessing it's a lot harder than regular 802.3,
because you have to deal with added things like spread spectrum,
encryption, and while I haven't studied it in depth, I would guess there
is something running even below TCP that deals with radio packet
sequencing.

Just my thoughts though, use at your peril :)

Josh
--
A common mistake that people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools.
       -Douglas Adams

"M. Adam Davis" wrote:
> I'd actually like more information about this, as I always considered
> 802.11 devices as simple packet devices - you give tham an ethernet
> packet, and they deliver it to all the other 802.11 devices in range.  I
> thought they took care of the physical layer completely.
>
> Is there something more to 802.11 devices that I wouldn't have to deal
> with on, say, an NE2000 ethernet card?

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2004\01\12@225429 by M. Adam Davis

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The most recent discussion on this list about it (IIRC) was someone
wanting to record several channels of audio simultaneously, and the
reason 802.11 was scrapped was because you couldn't gurantee latency,
and just like ethernet if things get too congested packets start
dropping like crazy.

I was considering making a wifi phone last year with a compact flash
wifi card.  Not enough time...  One of these days I'll poke around the
available source code.

Unfortunately they are becoming more like winmodems - the processing of
packets, error detection/recovery, etc are moving away from the card.
An example of this is the Intel centrino.

-Adam

Josh Koffman wrote:

{Quote hidden}

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2004\01\13@015039 by Jonathan Johnson

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check the transfer rate of the device(actual throughput rate). Decide on
what level of resolution and compression your intending to use, this will
give you a size per frame, multiply this by the number of frames per second
you want to transmit, if you want real time video you will need 25fps for
PAL or 30 for NTSC, this will give you your required data rate. If the first
figure is less the second, go back to drawing board. if the first figure is
larger than the second, then decide on how you are going to implement your
compression algorithm (software or FPGA etc), you should about now have a
serial stream which you need to convert to TCP/IP packets (XPORT? I dont
know its throughput) then you will need an 802.11 type bridge for your
ethernet packets to be sent over the WLAN. at the other end you either need
an access point or bridge to get your ethernet packets back, next you will
need either a decompression engine and a composite video out or some
software to receive and decode the packets, ready for display.

I think that should be a basic rundown of what you need to do(excluding a
step here or there, nothing substantial...I think), but dont quote me as I
havent done one myself before.....and I'm tired n hungry :-)


Cheers


JJ

{Original Message removed}

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