PIC to USB to 802.11g to USB to PC ?

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Hi all,

I'm usually just a lurker.  But now I'm getting interested in doing a link
from an 'F877 to a PC:

PIC s/w -> UART -> USB (adapter) -> 802.11g (adapter)  --//--> 802.11g
(adapter) -> USB -> Win XP -> app s/w


Have chosen neither the USB adapter nor the 802.11g adapter yet.  And I'm
fairly concerned about the potential complexity of USB and 802.11g protocols
that I will have to implement on the PIC side.

Any one have advice on any part of the above or pointers to some actual
implementations I could possibly leverage or adapt?

BTW, I'm leaning toward 802.11g rather than Bluetooth in order to achieve
higher (I think) outdoor range.  Any confirmation of that assumption?

TIA
--
...The Bit Eimer     NAR 84054      L0
"My goal in life is to be the kind of person my cat thinks he is"
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Re: PIC to USB to 802.11g to USB to PC ?
Your PIC side of the operation seems to be missing a piece.  I'm not aware
of any (simple) way to connect a RS232<->USB adapter directly to a WiFi unit
without involving a USB host such as a PC.  I think you have hinted at your
own fuzziness to this issue when you mentioned the complexity of USB and
802.11.  The easiest solution to your problem is to include a USB host so
that:

PIC ->UART-> USB -> PC HOST -> 802.11 ---//--->


I suppose including a PC in your PIC unit defeats the purpose of the simple
pic.  I know there are some simple WiFi modules available now for embedded
low volume stuff such as NetBurner, Digi(something) and probably a few
others.  Sounds like an interesting project.....


-Jim



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Re: PIC to USB to 802.11g to USB to PC ?

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That wasn't just a hint (wrt my fuzziness) - I am mostly a h/w type.  I am
really vague on what kind of s/w support is required for either the
UART-to-USB module or the USB-to-802.11g module.
All I really want to do is get packets from the PIC to my application in the
PC (about 150 meters away in outdoor terrain), but I'm sure there's all
kinds of maintenance functions that must be dealt with.

Of course, on the PC side, you not only have the processor to do the work,
but also all the canned drivers already done.  Is there nothing like that
available for the PIC that would ease the task of creating a 802.11g "radio
bridge"?

I guess in the worst case scenario, I could redesign my remote device to be
embedded-PC based, but man that will be overkill vis-vis its primary
function.


--
...The Bit Eimer     NAR 84054      L0
"My goal in life is to be the kind of person my cat thinks he is"
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Re: PIC to USB to 802.11g to USB to PC ?

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Bluetooth with external antennas works ok for 1-2 miles

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first of all 802.11g has lower range than 802.11b. Secondly there is
no easy way to connect 802.11g adapter to your PIC (there are no
rs232-usb adapters in this direction)

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no need to, just use bluetooth ... or you can use CARDBUS card, but
interfacing such a card is a b... not an easy task :), PCCARD is
easier, but there are no 802.11g pccards cards.

Pozdrawiam.
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Re: PIC to USB to 802.11g to USB to PC ?

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Any idea what kind of range one could expect from a bluetooth/USB dongle
(without external antenna)?


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Hmmm, my research led me to believe that g had more range than b (?).  Are
you thinking of a, perhaps, which has poor change due to higher freq?


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Can you recommend specific Bluetooth products that would interface well (or
easily) to a PIC?


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Thanks for your responses.

--
...The Bit Eimer     NAR 84054      L0
"My goal in life is to be the kind of person my cat thinks he is"
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Re: PIC to USB to 802.11g to USB to PC ?

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100m max, but it must be class 3 BT dongle (17dbm)
external antenna =
 http://flakey.info/antenna/omni/quarter /
for example, works great, costs pennies

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why ? same frequency, same power, less sensitivity and faster, why on
earth would you believe that you can get better range ?

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a has the same range (approximatelly) as g if you thing about 54Mbit
speeds (which are 34Mbit max in reality by the way :P)

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no :) but any RS232 BT would work, I would use one with integrated BT
stack, implementing your own stack my take a while (or two)

Pozdrawiam.
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Re: PIC to USB to 802.11g to USB to PC ?

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<snip>

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Mea culpa,  my source (the following article) discusses g vs a, not g vs b.
It appears g and b are about equilvalent on range, albeit not on data rate.

http://www.commsdesign.com/story/OEG20030114S0008


Thanks again.

--
...The Bit Eimer     NAR 84054      L0
"My goal in life is to be the kind of person my cat thinks he is"
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Re: PIC to USB to 802.11g to USB to PC ?

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great, but OFDM works at speeds >= 6Mbit/sec.
Every 802.11G chip falls back to CCK@5.5Mbit/sec DQPSK@2Mbit/sec and
DBPSK@1Mbit/sec if it cannot establish 6Mbit/sec link. And sensitivity
at >11Mbit/sec sucks. Those faster speeds are available only if strong
signal is present. Full 54Mbit (real 34Mbit) speed is only possible in
the same room :).

Pozdrawiam.
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RusH   //
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Re: PIC to USB to 802.11g to USB to PC ?
On Tue, 30 Nov 2004 23:49:12 -0700, in article
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There are UART to USB devices that are primarily meant as slave devices to
the HOST device the PC (See www.ftdi.com). These are relatively easy
because the hard work of USB is done in the host. Doing host side USB in an
embedded device can be done but is a lot of work, and normally involves
buying stacks for processors other than PIC. Various USB host devices have
been mentioned previously in this group.

However you also have the headache of 802.11g which normally involves
encapsulation of TCP/IP protocol. Some people have put stripped down
TCP/IP protocols onto a PIC (see the Lean TCP/IP book). Also note
TCP/IP is a bidirectional protocol.

The problem is you want to put potentially three heavy layers of software
onto a PIC, which I would not dream of doing.

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The first real question is not the mechanics of which 'bits' to use but
what is the data transfer?

How much data for how long and how often?

Your basic system is

        PIC --> some link --> PC

If your data rates are low you could probably use a telemetry band device
with potentially a modem encoder chip to get 2400 to 9600 baud, or even
buy a radio modem device. Especially if the data direction is
unidirectional.

For high or very high data rates I would doubt the PIC could keep up.

Alternatively get a 802.11g module that is menat for interfacing to an
embedded system that deals with the protocols etc.. Meaning you have
a more complex micro dedicated to the link. There have been some articles
in Circuit Cellar www.circuitcellar.com, about doing that sort of thing.

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802.11g is packet driven but usually an encapsulation of TCP/IP so quite a
bit of software.

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First of all it would be more helpful to know what the data rate and packet
sizes are to give a meaningful response.

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<http://www.pcserviceselectronics.co.uk/ PC Services
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Re: PIC to USB to 802.11g to USB to PC ?

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<snip>

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Thanks for these explanations.  Sounds like 802.11 is simply too loaded up
with capabilities for me to easily make use of.  Others suggest Bluetooth,
though I would have all the
same questions about that technology.


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Actually, the comm is bidirectional.  At this stage I would estimate my
PC-to-remote data rate requirement at about 30k bits/sec; remote-to-PC at
about 5k bits/sec with the possibility of 2 remote devices, each at that
rate.  Packet sizes vary from 4 bytes up to 20 bytes.

At one point I was considering a 900 MHz linksys transciever, but I can't
deal with the licensing issue.

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Thanks, I'll go looking.


<snip>


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See above.



Thanks for your response.

--
...The Bit Eimer     NAR 84054      L0
"My goal in life is to be the kind of person my cat thinks he is"
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Re: PIC to USB to 802.11g to USB to PC ?

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................


5Kbits/sec can be done easily on standard telemetry bands with modem chips
(10KHz or 25KHz channel bandwidth most authorities don't like people
 using n channels witdth for higher rates). However with two remote systems
you would need a separate channel (RX/TX) pair for each remote or time
slicing issues.

30kbps is difficult on standard license free telemetry bands in most
countries. But you might squeeze the data rate into a 25KHz channel with
an appropriate modem chip (33kps modems chip POSSIBLY).

However even with using 433/459MHz sets you have the issues of cost.

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Steer clear of anything requiring licensing, but be aware that license exempt
bands still need to be dealt with carefully for other users on the same band.
This is also true for ANY wireless band you use (bluetooth, 802.11x etc.).

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It is not a simple requirement.

--
Paul Carpenter          | snipped-for-privacy@pcserviceselectronics.co.uk
<http://www.pcserviceselectronics.co.uk/ PC Services
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Re: PIC to USB to 802.11g to USB to PC ?

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Sounds unnecessarily complex, why not just connect an 802.11b PCMCIA
or CF card directly to the PICmicro? It might be a bit tricky because
of the small amount of RAM on the PIC16F877, but a PIC18F452 works
just fine.

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You don't have to understand the inner workings of 802.11, as the WLAN
card processor does all the hard work; once set up, it provides a raw
data link similar to Ethernet. You can invent your own communication
protocol to run over this link, but most people use TCP/IP. If you're
a newcomer to this protocol family I'd suggest checking out UDP,
because it is realtively easy to implement and debug.

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 www.iosoft.co.uk

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I don't know much about Bluetooth, but the usual quoted range seems to
be 10 meters (32 feet) as opposed to 100 meters or more for 802.11 -
but of course this depends on the type of antennas, obstructions etc.

Jeremy Bentham
Iosoft Ltd.


Re: PIC to USB to 802.11g to USB to PC ?
Hi,

indeed, by using modules you don't have to worry about WLAN driver or
TCP stacks.

The company I work for builds modules which connect to WLAN on one side
an RS232 on the other side. By using simple "AT" commands or by
configuring the module over a website you can set up a connection to
another modul, to a PC or to the Internet. Your PIC does not need any
protokoll stuff.

Take a look at www.avisaro.com . Contact me if you need an English
speeking person.

If you are concerned about outdoor range, use 802.11b rather than
802.11g . The rule of thumb is: the higher the bandwith the lower the
range.

Most Bluetooth modules have a range of 10m, only a few provide 100m.
The main difference is the protokoll: if you need network connectivity,
you don't get TCP or UDP with Bluetooth modules (at least the one I
know). If you only need a point to point connection, you are fine with
bluetooth.

Matthias Colsman
Avisaro AG


Re: PIC to USB to 802.11g to USB to PC ?
Dass sieht interesant aus, aber die Frage ist, uber wieviel Meter kann mann
diese WLAN benuetzen?  Dass habe ich nicht gefunden auf deine Website.

(Ja, ich weiss, mein Deutsch ist beschissen)

--
...The Bit Eimer     NAR 84054      L0
"My goal in life is to be the kind of person my cat thinks he is"
We've slightly trimmed the long signature. Click to see the full one.
Re: PIC to USB to 802.11g to USB to PC ?

The range of WLAN is typically 300 meter outdoors and 30-50 meter
indoor (through walls and sealings). This holds true for the Avisaro
Moduls as well.

If you have lots of steel and concrete around you, the range is at its
lower end - with wood and open space the range is at its higher end.
Hope that helps.

Matt


Re: PIC to USB to 802.11g to USB to PC ?
Hi,

indeed, by using modules you don't have to worry about WLAN driver or
TCP stacks.

The company I work for builds modules which connect to WLAN on one side
an RS232 on the other side. By using simple "AT" commands or by
configuring the module over a website you can set up a connection to
another modul, to a PC or to the Internet. Your PIC does not need any
protokoll stuff.

Take a look at www.avisaro.com . Contact me if you need an English
speeking person.

If you are concerned about outdoor range, use 802.11b rather than
802.11g . The rule of thumb is: the higher the bandwith the lower the
range.

Most Bluetooth modules have a range of 10m, only a few provide 100m.
The main difference is the protokoll: if you need network connectivity,
you don't get TCP or UDP with Bluetooth modules (at least the one I
know). If you only need a point to point connection, you are fine with
bluetooth.

Matthias Colsman

Avisaro AG


Jeremy Bentham wrote:
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a link
802.11g
And I'm
protocols
WLAN
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achieve
assumption?
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to


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