[query]wireless serial data modem

Hi,

I am looking for a device, with following functionality

1) Takes input data from a serial/SPI interface (Data given to
serial/SPI interface from a 8051-based micro-controller)
2) Outputs data in 802.11b format
3) Support for antenna would be advantageous to extend the range of
device.

I think a typical wireless serial data modem works as a solution for my
requirement.
I could find 'hopnet 208' but the antenna is of low transmit power. Can
anyone suggest similar devices or any others which solves my problem
with low cost !

Any links/forums/related material will also do.

Thanks & Regards,
Dinakar

dinakar31 wrote:

> I am looking for a device, with following functionality
>
> 1) Takes input data from a serial/SPI interface (Data given to
> serial/SPI interface from a 8051-based micro-controller)
> 2) Outputs data in 802.11b format
> 3) Support for antenna would be advantageous to extend the range of
> device.
>
> I think a typical wireless serial data modem works as a solution for my
> requirement.
> I could find 'hopnet 208' but the antenna is of low transmit power. Can
> anyone suggest similar devices or any others which solves my problem
> with low cost !

What's your level of electronics expertise? How much are you willing to
pay? I've seen $1000 data loggers that can do this, and I've seen cheap
components that can be put together to do it, but I can't manage to find
any reasonably priced combos.
--
derek

"dinakar31" <(E-Mail Removed)> hath wroth:

>I am looking for a device, with following functionality
>
>1) Takes input data from a serial/SPI interface (Data given to
>serial/SPI interface from a 8051-based micro-controller)

That would be RS-232

>2) Outputs data in 802.11b format

Why? 802.11b is nothing more than encapsulated ethernet 802.3
packets. Anything that talks ethernet will work over 802.11b.
However, RS-232 is not ethernet and requires additional conversions to
make it work. Better for a proprietary protocol that does RS-232 and
forget about 802.11b or whatever.

>3) Support for antenna would be advantageous to extend the range of
>device.

Antenna mounting devices are usually included with the antenna. What
type of "support" were you thinking?

>I think a typical wireless serial data modem works as a solution for my
>requirement.

What are you requirements? (Numbers, not descriptions).

>I could find 'hopnet 208' but the antenna is of low transmit power. Can
>anyone suggest similar devices or any others which solves my problem
>with low cost !

Do you have any numbers in mind? Perhaps some clue as to the thruput
requirements, range, AC/DC power, and such would also be helpful. Most
of the 900MHz serial links cannot do faster than 115kbits/sec thruput.

While you're getting your numbers together, look at the various 900MHz
products from:
http://www.freewave.com
http://www.avalanwireless.com (ethernet only)
http://www.rflinx.com
and anything else that Google returns for "RS-232 wireless modem".
There are quite a few. Do you need point-to-multipoint? Freewave
will do that.

900MHz external yagi antennas are fairly common.
http://www.pacwireless.com/products/yagi_900mhz.shtml

Do you have an existing datalogger? Any particular make and model?

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

SPI and EIA232 are different. For one thing, SPI feeds a clock signal.
I could go on, but I think the only solution is simply to read the SPI
data input a PC, probably by bit banging, then feeding the data out a
usb or ethernet port to stock wifi gear.

Jeff Liebermann wrote:
> "dinakar31" <(E-Mail Removed)> hath wroth:
>
> >I am looking for a device, with following functionality
> >
> >1) Takes input data from a serial/SPI interface (Data given to
> >serial/SPI interface from a 8051-based micro-controller)
>
> That would be RS-232

Look at this product. I use a lot of there devices and have found them
to be very reliable and work very well.



NPort W2250/2150
2-port and 1-port Wireless Serial Device Servers

Quickview


View Larger Picture



Features Datasheet (PDF)
Specifications Documentation & Drivers
Serial-to-Wireless Flash Demo NEW!
Ordering Information

Link any serial device to a Wi-Fi 802.11b network
2 or 1 RS-232/422/485 ports, at up to 230.4 Kbps




Introduction


The NPort W2250/2150 Wireless Serial Device Server extends wireless
networking capabilities to printers, scales, medical equipment,
manufacturing machinery, bar code readers, card readers, point-of-sale
equipment and other data collection devices. NPort W2250/2150's
RS-232/422/485 3-in-1 serial interface is suitable for use with most
serial devices. Link up to 2/1 serial devices to your wireless network
via one NPort Server IP address.
More info >>

I am a software engineer and I have an embedded electronics engineer in
my team. We are looking for devices as cheap as possible, may be less
than $20 but can go upto $30 to $40.
Can u suggest me some cheap components that can be 'put together' in
reasonable amount of time ?

> >2) Outputs data in 802.11b format
>
> Why? 802.11b is nothing more than encapsulated ethernet 802.3
> packets. Anything that talks ethernet will work over 802.11b.
> However, RS-232 is not ethernet and requires additional conversions to
> make it work. Better for a proprietary protocol that does RS-232 and
> forget about 802.11b or whatever.

I think I did not explain clearly. I'll put again. My communication
medium is wireless at 2.4GHz (wifi/802.11b standard) & in a range of
120 - 150 meters. I want this complete thing cheaper. So, using a
micro-controller I want to send data to a device and the device should
be able to convert this and should be outputting wireless data
confirming to 802.11b stds.
At the receiver side, I can go for a slightly costly device.
As u have said, getting software for conversions would be
costly.

> >3) Support for antenna would be advantageous to extend the range of
> >device.
> Antenna mounting devices are usually included with the antenna. What
> type of "support" were you thinking?

By support, i just mean that I would be able to connect an antenna to
the device. Also, I'm looking for the device to be powered by DC.

> >I think a typical wireless serial data modem works as a solution for my
> >requirement.
> What are you requirements? (Numbers, not descriptions).
By requirements, I mean the 1), 2), 3) points mentioned in 'start of
this topic'. I don't need any DHCP, web servers or any other
functionality in the device(as it increases the cost). I just want the
device to transmit the data(obtained thru serial interface) wirelessly.
Data rate of device is also not of a concern.

> >I could find 'hopnet 208' but the antenna is of low transmit power. Can
> >anyone suggest similar devices or any others which solves my problem
> >with low cost !
>
> Do you have any numbers in mind? Perhaps some clue as to the thruput
> requirements, range, AC/DC power, and such would also be helpful. Most
> of the 900MHz serial links cannot do faster than 115kbits/sec thruput.
> While you're getting your numbers together, look at the various 900MHz
> products from:
> http://www.freewave.com
> http://www.avalanwireless.com (ethernet only)
> http://www.rflinx.com
> and anything else that Google returns for "RS-232 wireless modem".
> There are quite a few. Do you need point-to-multipoint? Freewave
> will do that.
>
> 900MHz external yagi antennas are fairly common.
> http://www.pacwireless.com/products/yagi_900mhz.shtml
>
> Do you have an existing datalogger? Any particular make and model?
>
> --
> Jeff Liebermann (E-Mail Removed)
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060 http://802.11junk.com
> Skype: JeffLiebermann AE6KS

"dinakar31" <(E-Mail Removed)> hath wroth:

>I think I did not explain clearly. I'll put again. My communication
>medium is wireless at 2.4GHz (wifi/802.11b standard) & in a range of
>120 - 150 meters.

OK. Those are the only numbers I've seen other than the SPI/Serial
interface and the $20-$40 cost per end.

There are kits that can do what you want sold for OEM development. For
example:
http://www.linxtechnologies.com
http://www.lprs.co.uk
http://www.rfsolutions.co.uk
http://www.lemosint.com

http://www.parallax.com/html_pages/p...rf_modules.asp
http://www.maxstream.net/products/
http://www.datahunter.com/products.html (nifty stuff)
http://rf-modules.globalspec.com
However, few of these are 802.11b compatible or will meet your cost
objective in small quantities. Why do you need 802.11b compatibility?
You're just sending serial data, not ethernet.

Speaking of serial data, is it bi-directional or do you just need to
stream bits to the data logger? If so, then the unidirectional
(simplex) radio is MUCH simpler and cheaper (if you dump the 802.11b
requirement).

The level of intergration is not terribly clear. Do you need chips to
intergrate into a design or a complete module ready to plug and play?

You'll find that data rate and range mutually affect each other. You
can easily do 150 meters at 2.4Ghz, but only at fairly slow data rates
or with a big directional antenna. Similarly, you can obtain MHz data
rates, but not over a very large distance.

I would be tempted to suggest you look into using the common MiniPCI
wireless cards, which will certainly be under $40 and are 802.11b
compliant. However, interfacing your contrivance with a PCI bus may
not be possible. 2nd best might be to just purchase a USB 2.4GHz
dongle and deal with the interface issues. The problem there is
software as much of the MAC layer is implimented in the off chip
processor (driver).

I dunno. Good luck.







--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:

> However, few of these are 802.11b compatible or will meet your cost
> objective in small quantities. Why do you need 802.11b compatibility?
> You're just sending serial data, not ethernet.

Hey Jeff, I'm confused by your confusion :-)

He's got an 802.11 infrastructure, and he doesn't have wires running from
the serial device to the PC - so if his device could encapsulate that data
in ethernet packets, any other device on the network would be able to
receive them.

How do you send serial data wirelessly without using _some_ sort of wireless
protocol?
--
derek

Derek Broughton <(E-Mail Removed)> wrote:
>He's got an 802.11 infrastructure, and he doesn't have wires running from
>the serial device to the PC - so if his device could encapsulate that data
>in ethernet packets, any other device on the network would be able to
>receive them.

It's not clear that it's truly RS-232 serial data, or some kind of SPI
or other clocked serialized data link. If it's truly RS-232, he could
probably use an Ethernet RS232 port (Google for "rs232 ethernet" gets
some hits, for instance) and a client-mode AP.

>How do you send serial data wirelessly without using _some_ sort of wireless
>protocol?

You might need some protocol, but it wouldn't nessesarily be 802.11

You could use a CW transmitter, and a crystal detector with no
protocol if you just wanted _those_ bits over _here_...