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 RS232USB 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

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"
[remove keinewurst and reverse letters in domain to email me]
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Bluetooth with external antennas works ok for 1-2 miles

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)

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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Like ninjas, true hackers are shrouded in secrecy and mystery.
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There are UART to USB devices that are primarily meant as slave devices to the HOST device the PC (See

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.

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

about doing that sort of thing.

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

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

--
Paul Carpenter          | paul@pcserviceselectronics.co.uk
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Any idea what kind of range one could expect from a bluetooth/USB dongle (without external antenna)?

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?

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

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"
[remove keinewurst and reverse letters in domain to email me]
--------------------------------------------------------------

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.

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.

Thanks, I'll go looking.

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"
[remove keinewurst and reverse letters in domain to email me]
--------------------------------------------------------------

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

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.

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.).

It is not a simple requirement.

--
Paul Carpenter          | paul@pcserviceselectronics.co.uk
    PC Services
              GNU H8 & mailing list info
             For those web sites you hate

100m max, but it must be class 3 BT dongle (17dbm) external antenna = for example, works great, costs pennies

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

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

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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RusH   //
 http://randki.o2.pl/profil.php?id_r=352019
Like ninjas, true hackers are shrouded in secrecy and mystery.
You may never know -- UNTIL IT'S TOO LATE.

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.

Thanks again.

--
...The Bit Eimer     NAR 84054      L0
"My goal in life is to be the kind of person my cat thinks he is"
[remove keinewurst and reverse letters in domain to email me]
--------------------------------------------------------------

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.

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.

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.

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   //
 http://randki.o2.pl/profil.php?id_r=352019
Like ninjas, true hackers are shrouded in secrecy and mystery.
You may never know -- UNTIL IT'S TOO LATE.

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

. 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

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

. 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:

a link

802.11g

And I'm

protocols

WLAN

actual

achieve

assumption?

to

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" [remove keinewurst and reverse letters in domain to email me]

--------------------------------------------------------------

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