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HomeSchoolDad
08-20-2005, 11:18 AM
I need 6 stamps to talk to a base PC and the embedded blue option looks like the winner to me, but I need to be sure about a few things before I commit. As the man says "don't fail to plan"! Please give any comments about your experience (positive or negative) if you have experience with this module - I would appreciate it VERY much.

Specifically, does anyone know:

(1) if the normal 7 connections can be made at the same time?

(2) if the connection is secure and can not be hijacked?

(3) if the range is REALLY up to 300 feet when the rest I see are only 30 feet?

(4) if another wireless option might be better suited?

Thank you for any help you can be.

Jeff

Chris Savage
08-20-2005, 11:44 AM
Jeff,

I can answer for a couple of your questions...7 connections at one time would require 14 units, connected in pairs. Only one unit can connect with one other unit at a time by Mac Address. You cannot connect to multi units. As for the range, it's open field range, based on ideal conditions, I'm sure. You can bet that indoors with walls and things that will cut down the range. As for why it's more than typical blue tooth modules, there's a 10X amplifier on the board.

You can also get some information from the product documentation, which can be downloaded in PDF format at the following link. http://www.parallax.com/dl/docs/prod/comm/eb500.pdf

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Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)

HomeSchoolDad
08-20-2005, 08:21 PM
Hi Chris,

Thanks for the post. Let me be sure I understand. If the PC has a unit and there are two other remotes I can not connect the PC to both of the remotes at the same time - I would have to connect to one, talk to one, drop the connection, connect to the other, talk, drop the connection, rinse hair thouroughly and repeat.

Since the connection is made by MAC address, it cannot be hijacked (easily) and the encryption makes it secure.

Do I have it?

Is there another wireless option that is better suited for multiple connections?

Thanks again for the post!

Jeff

Chris Savage
08-20-2005, 11:49 PM
Jeff,

Yes, each EB500 module can only connect to one other. That's not to say that there's not some piece of computer hardware that won't connect to multiple EB500 units, but I am not aware of one. You could contact support at www.a7eng.com (http://www.a7eng.com) to see if they can give you more details than what we have as they are the manufacturer of the units and might have more information.

As for the MAC address the units can broadcast their I.D., but I don't think they broadcast their MAC Address. There is code to retrieve that from the module using the BASIC Stamp. It's a pretty secure connection, but of course to some that is a matter a perspective. I can't think of an alternative BlueTooth solution.

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Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)

knightofoldcode
08-21-2005, 07:19 AM
Chris Savage (Parallax) said...
Jeff,
As for the MAC address the units can broadcast their I.D., but I don't think they broadcast their MAC Address. There is code to retrieve that from the module using the BASIC Stamp. It's a pretty secure connection, but of course to some that is a matter a perspective. I can't think of an alternative BlueTooth solution.


Very much a matter of perspective. You're never going to get a true secure connection. All you can do is a get a "good enough" connection. For an example..... DirecTV spent millions of dollars getting thier products to be "un hackable" and they hailed it as being so! However, there is still DirecTV hacking going on, even on thier new generation cards that are "unhackable".

You'll just have to find out how difficult it would be and decide if it's a good enough connection for your application.

Knight.

Chris Savage
08-21-2005, 08:03 AM
Knight,

You kind of said what I was thinking... =)

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Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)

HomeSchoolDad
08-21-2005, 11:49 AM
Yea, I tell my customers that it isn'tif your system gets cracked (or at least an attempt at a crack), it is when you get cracked - so you have to stay proactive in staying safe. But you can only do so much. I think I am good taking the path of a locked car (it keeps the basically honest people out).

OK, BlueTooth is secure (enough) and meets the distance requirement - but I need a base station that talks to 6 handhelds and I don't know when any one of them might want to send data or a request to the pc. Does that mean that I need 12 transievers - and 6 of them all connected to the same PC???

I noticed that one of the non-bluetooth units has a switched mode that seems to indicate that I can have all 6 remotes using different addresses and have the master pc looking for a packet from any of them. Can I use the same technique here with the moving from mac address to mac address - or is the overhead time too high?

I don't think I can use the other units because I have another system that I am fairly sure runs on the 433mhz frequency already that is in place alongside of this unit.

Advice? Anyone?

Chris Savage
08-21-2005, 01:27 PM
I would definately contact Bryan over at www.a7eng.com (http://www.a7eng.com) to see if he has a solution for your requirements.

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Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)