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Netduino and RFIDs

RFID

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#1 JamieDixon

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Posted 31 March 2013 - 12:57 PM

This easter morning my son and I are trying to create a self-hinting easter egg hunt.  We started using the Phidget RFID receiver and keytags, the problems are:

1) Phidgets are teathered to the PC, a dragging a PC around on a easter egg hunt is sub-optimal

2) The range of the RFID is 3 inches at best, which is also sub-optimal.

 

I then thought of using a Netduino with a higher powered RFID that can calculate the distance so we can have the board signal cold,warm, and hot as the person gets closer to the egg.  I Googled on Bing, searched this this forum and went to sparkfun - but no luck. 

 

Any ideas?



#2 JerseyTechGuy

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Posted 31 March 2013 - 02:25 PM

I cannot give you exact resources of where and what to get but I can tell you from having worked on a related project these are typcially called EPC RFID tags, EPC meaning Electronic Product Code.  The latest I think is EPC Gen 2.  These are the kind of high powered tags used in Drivers licenses and other ID Cards as well as products so they can be inventoried from up to 30 feet.

 

The problem with most typically RFID key fobs and the like is they are not powered.  They are powered when the EM field is created between the reader and the tag and info is sent back. The only ways around this is creating a larger EM field or powering the tags.

 

Hope this will help with the Googling of resources.



#3 JamieDixon

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Posted 31 March 2013 - 08:48 PM

Yeah -We were thinking of having a high-powered lighthouse/beacon next to the egg that would have their own power source.  I'll check out EPC Tags.

 

Thanks



#4 mtylerjr

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Posted 02 April 2013 - 02:18 AM

Hi Jamie

 

I've been an RFID software/firmware specialist for the past 8 or 9 years, and I've been thinking (on and off) about developing an RFID project for one of the netduino platforms. As far as Ive seen, no one has really done much of anything with RFID on the netduinos.

 

For your application, you would need to use a UHF band around the 900Mhz range, most likely C1G2 (class one, generation 2) - which can read passive (unpowered) tags up to about 30 meters (100 feet).

 

Most C1G2 readers provide a values known as RSSI (Relative Signal Strength Indicator) in the response from a tag, but it is not as straightforward as you might think, to use this value to determine actual distance - especially using only one reader. UHF signals are notorious for bouncing around and arriving via circuitous routes (this is called "multipath") - so you wouldn't be able to rely on that measurement too closely.

 

But if you want to experiment with UHF/C1G2 RFID there are many off the shelf products you can play with. One that Ive had my eye on is this one: http://www.digitimes...D=4455&tag=2035

 

It's a C1G2 USB dongle - you could plug it into your mobile phone and then the software to do what you wanted to do would be relatively easy (although, because of multipath, it wouldn't be 100% reliable as a distance measurement)

 

There are also non-USB C1G2 modules that someone could use with the netduinos, and a simple little SPI or TTL driver, such as this one: http://www.rfidinfo....02954448600.pdf - wiring one of those up to a standard STM8 module should be trivial, provided you can scour through the forums to find the correct information on how to build the STM8 standard firmware - something Ive yet to be able to do. :)



#5 jbrowne

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Posted 07 May 2013 - 06:49 PM

Hi Jamie

 

I've been an RFID software/firmware specialist for the past 8 or 9 years....

Could you help answer a question for me?

I've got an proprietary access control system that I installed and manage for my company. It is from kerisys

I wanted to know if it would be possible to hook up one of the readers from the system (which uses a RS485 interface) to a netduino ?

how would I know what or how to program the interface to read from this reader.  I do not even know at what frequency the tags are - I suspect it's the longer range frequency.

 

I have successfully gotten my netduino to read tags from a uart/serial RFID reader (RDM630).



#6 JamieDixon

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Posted 09 May 2013 - 11:11 AM

Ahhh.  You have 8 to 9 years more experience than me!!!  I have no idea about those interfaces and devices.  I would re-ask the question in the forums and have someone who knows what they are talking about answer them.

 

Sorry I can't be more of a help...



#7 jbrowne

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Posted 09 May 2013 - 11:53 AM

oops.

i can see that i was too fast in my post.

 

i was directing that to: mtylerjr

and was quoting his post to you.

 

sorry for the confusion.

 

mtylerjr - do you think you can answer the question?

 

thanks.



#8 nakchak

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Posted 09 May 2013 - 12:11 PM

oops.

i can see that i was too fast in my post.

 

i was directing that to: mtylerjr

and was quoting his post to you.

 

sorry for the confusion.

 

mtylerjr - do you think you can answer the question?

 

thanks.

 

You would need to create a RS485 interface to the ND first, i think Maxim make some SPI controllable chips that do that, once that's working you would need to get the specs of the readers protocol and program the ND to communicate with the reader. 

 

Reading shouldn't be a problem, but you may find that writing is not possible as the vendor may well have keys set up on the cards to prevent unauthorized writing.

 

If you can teardown a reader and see if its a commercial reader rebadged by the vendor, most access systems i have dealt with (used to work in the cashless vending/access control business) have used off the shelf modules rebadged so going to the module makers site has often given me the full data sheet for the device.

 

Nak.







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