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From: Mitch Crane on 22 Nov 2006 20:31

Does anyone have the pinout for the GA800BT WiFi board. I know it's
actually connected to a USB port.

Below is what I have. I'm sure of everythig but the ones marked 'nc'
(just guessing that they aren't connected).


3
. g
3 n n n D D 5
v c c d - + v

o o o o o o o
o o o o o o

n n g n n 5
c c n c c v
d


There is also a row of through-holes above the Realtek chip which are
labeled 5v, D1-, D1+, GND, NC, NC in that order.

I'm curious as to whether this thing will run without the 3.3v (I'm
guessing not) and if I can make my own cable to use it with another PC.

Any suggestions on a circuit to convert the 5v to 3.3v and use that
would be appreciated.

--
ybbxvatyvxrnobeantnvayvivatyvxrnurergvpyvfgravatgbneguheyrrerpbeqfznxv
atnyylbhesevraqfsrryfbthvyglnobhggurveplavpvfznaqgurerfgbsgurvetrareng
vbaabgriragurtbireazragnertbaanfgbclbhabjohgnerlbhernqlgborurnegoebxra
From: Paul on 23 Nov 2006 02:51
Mitch Crane wrote:
> Does anyone have the pinout for the GA800BT WiFi board. I know it's
> actually connected to a USB port.
>
> Below is what I have. I'm sure of everythig but the ones marked 'nc'
> (just guessing that they aren't connected).
>
>
> 3
> . g
> 3 n n n D D 5
> v c c d - + v
>
> o o o o o o o
> o o o o o o
>
> n n g n n 5
> c c n c c v
> d
>
>
> There is also a row of through-holes above the Realtek chip which are
> labeled 5v, D1-, D1+, GND, NC, NC in that order.
>
> I'm curious as to whether this thing will run without the 3.3v (I'm
> guessing not) and if I can make my own cable to use it with another PC.
>
> Any suggestions on a circuit to convert the 5v to 3.3v and use that
> would be appreciated.
>

You can use a three terminal regulator (TO-220 package is nice), and
a couple bypass capacitors, to drop the 5V to 3.3V. There are a lot
of different models of devices like this for sale on Digikey.com .

http://www.onsemi.com/pub/Collateral/CS52015-3-D.PDF

If you draw that power from the 5V USB feed, there is a limit of
500mA per port. If you use that 5V to feed the 3.3V regulator,
what you don't know, is how much current they are drawing
from 3.3V. It could be, that the sum of the 5V power (for the
USB portion of the design), plus the 3.3V, would exceed the
500mA limit.

An easier way to solve the problem, is to pick up 3.3V from the power
supply, and send it to the module. If you do that, it might be a good
idea to put a fuse in the circuit, as shorting the home-brew 3.3V
feed, could draw 30 amps. Even a 5 amp Picofuse would add a measure
of safety, or a Polyfuse if you could find one in a useful package.

Another thing you don't know, is if there is a sequence requirement
for the rails. Does 5V rise before the 3.3V rail on the WiFi module,
or is it the other way around. Some logic devices have specific
requirement for which rail powers up first.

You could just leave the module in the box, with all the other
accessories. The module isn't worth that much, and is probably
not worth the trouble of trying to salvage it.

If you can see the part number on the MAC chip or the PHY
etc., you may be able to download a datasheet for the
thing, and see what kind of current it draws, and how
feasible it is to extract power from the 5V USB.

Paul
From: Mitch Crane on 23 Nov 2006 12:38
Paul <nospam(a)needed.com> wrote in
news:ek3jp7$hmq$1(a)aioe.server.aioe.org:

> Mitch Crane wrote:
>> Does anyone have the pinout for the GA800BT WiFi board. I know it's
>> actually connected to a USB port.
>>
>> Below is what I have. I'm sure of everythig but the ones marked
>> 'nc' (just guessing that they aren't connected).
>>
>>
>> 3
>> . g
>> 3 n n n D D 5
>> v c c d - + v
>>
>> o o o o o o o
>> o o o o o o
>>
>> n n g n n 5
>> c c n c c v
>> d
>>
>>
>> There is also a row of through-holes above the Realtek chip which
>> are labeled 5v, D1-, D1+, GND, NC, NC in that order.
>>
>> I'm curious as to whether this thing will run without the 3.3v (I'm
>> guessing not) and if I can make my own cable to use it with another
>> PC.
>>
>> Any suggestions on a circuit to convert the 5v to 3.3v and use that
>> would be appreciated.
>>
>
> You can use a three terminal regulator (TO-220 package is nice), and
> a couple bypass capacitors, to drop the 5V to 3.3V. There are a lot
> of different models of devices like this for sale on Digikey.com .
>
> http://www.onsemi.com/pub/Collateral/CS52015-3-D.PDF

Thanks, Paul. I'll check that out.

> If you draw that power from the 5V USB feed, there is a limit of
> 500mA per port. If you use that 5V to feed the 3.3V regulator,
> what you don't know, is how much current they are drawing
> from 3.3V. It could be, that the sum of the 5V power (for the
> USB portion of the design), plus the 3.3V, would exceed the
> 500mA limit.

Yeah, I had considered this. I run a 40GB laptop drive off one of my
USB port and drawing its power from the port which I would think would
draw more current that this board would, but I realize that I could be
wrong there.

> An easier way to solve the problem, is to pick up 3.3V from the
> power supply, and send it to the module. If you do that, it might be
> a good idea to put a fuse in the circuit, as shorting the home-brew
> 3.3V feed, could draw 30 amps. Even a 5 amp Picofuse would add a
> measure of safety, or a Polyfuse if you could find one in a useful
> package.

I had considered getting the 3.3v that way as well, but my plan is to
mount this board in a plastic box and cut one end off of a USB cable
which I would wire up to the board. So the end result would be a
plastic box with an antenna connection on one side and a 6 ft. USB
cable coming out the other.

I may find that it would be cheaper just to go out and buy a USB WiFi
dongle, but that takes all the fun out of it.

> Another thing you don't know, is if there is a sequence requirement
> for the rails. Does 5V rise before the 3.3V rail on the WiFi module,
> or is it the other way around. Some logic devices have specific
> requirement for which rail powers up first.

Good point, and something I hadn't considered.

> You could just leave the module in the box, with all the other
> accessories. The module isn't worth that much, and is probably
> not worth the trouble of trying to salvage it.

It's probably not worth it. In fact, a quick check at dealnews.com
pretty much answers that question. I see one WiFi dongle for $0 after
rebate and a D-Link DWL-G120 AirPlus G 802.11g which was recently $5
after rebate ($10 at the moment).

> If you can see the part number on the MAC chip or the PHY
> etc., you may be able to download a datasheet for the
> thing, and see what kind of current it draws, and how
> feasible it is to extract power from the 5V USB.

Yeah I couldn't find a data sheet on the RealTek chip (RTL8187L) all
though I didn't do an exhaustive search. The board is an AzurWave AW-
GA800BT.

--
ybbxvatyvxrnobeantnvayvivatyvxrnurergvpyvfgravatgbneguheyrrerpbeqfznxv
atnyylbhesevraqfsrryfbthvyglnobhggurveplavpvfznaqgurerfgbsgurvetrareng
vbaabgriragurtbireazragnertbaanfgbclbhabjohgnerlbhernqlgborurnegoebxra
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