Programming RFID tags

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When I was first playing around with RFID I bought 3 collar tags from China that were supposedly programmable that I came across yesterday in my RFID drawer.  At the time I got the feeling they were legally sketchy.  The are the same diameter and shape as typical tags, but much thicker.  The insides don't rattle around inside the tag like the cat tags I've been using.  They give great range with my 125kHz circuit.  When read they all give FFFFFFFFFF for the tag number.  If I have to build a modulated 125kHz signal I'm afraid I will be out of my depth.  I am using EM4095 chips to generate and read the RF field, and am wondering if I can use the same chip to somehow program the collar tags.  I never got a datasheet for the things.  Any iseas?

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MarkThomas wrote:
I never got a datasheet for the things.  Any iseas?

 

Yes,

Send them to teh scrap and just buy the ones you want on ebay for a few sheckles and save the advil for a better headache laugh

 

Jim

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jgmdesign wrote:
Send them to teh scrap and just buy the ones you want on ebay for a few sheckles and save the advil for a better headache laugh

Yeah, you are probably right.  For some reason at the time I thought it would be fun to game the system and make duplicates.  A headache, probably.  As it is I have 3 with the same ID number FFFFFFFFFF, with great range.  I can still use them.

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There used to be an excellent MicroChip app note for pretty much any flavour of rfid chips, including the programmable types. From what I have read in passing (we don't use 'em) they all seem to use a similar technique to program. Sadly, my google-fu is weak and I have been unable to find that app note recently.

 

Neil

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OK, thanks Neil. 

 

I will search around for it.  My Goggle is not that great either.  I suspect that what it takes to program those collar tags is going to be beyond me anyway.  It was just a lark a long time ago, and I came upon them when I was looking in the RFID bin the other day.  They have great range.  I also found some little tags that look like miniature railroad spikes I had also forgotten about.  They have a range about the same as the cheap eBay tags from years ago.  I only have one cat that needs a tag, so it is pretty easy.  Probably as Jim suggests the tags on eBay these days are a lot better than what was typical 9 or 10 years ago.  I will let you know if I find that app note.  Thanks again,

 

mark  

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Neil,

I found this 3MB pdf app note:   http://ww1.microchip.com/downloads/en/devicedoc/51115f.pdf  that is sort of amazing.  Lots of general RFID info, MathLab code, Pic code, pages of equations for mutual inductance of antennas, and specifics for Microchip microID@ devices.  I don't know if this is the one you remember, but it seems to have all things RFID.  It has a 2004 date on it.

mark

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That looks about right Mark, thanks. Enjoy getting your teeth into that one :)

 

Neil

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Neil,

O Man, there is a lot there.  Included are data sheets for a Microchip MCRF200 and MCRF250 that are the tag end chip, and are contactlessly programmable.  Those parts appear to be obsolete, and are not available on DigiKey and Microchip shows data not available and not recommended for new designs.  I've gotten obsolete chips from China.  I remember inputting a part number and getting responses from multiple vendors, maybe AliBaba.  I could probably get some if I wanted to go there.  I have never played with the tag end of things except to buy tags.  An interesting claim in the MCRF250 data sheet follows:

 

The MCRF250 is equipped with an anti-collision
feature that allows multiple tags in the same field to be
read simultaneously. This revolutionary feature
eliminates the issue of data corruption due to
simultaneous transmissions from multiple tags.

 

I dont know if I am up to building an AM board, to program the things, but 125kHz is low enough I might be able to get away something.  Somehow such a project grabs me.  I've been looking for something besides LEDs to focus on, and RFID has always been my first love electronically.  Thanks!

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I looked on DigiKey under "RFID Transponders, Tags" for 100-150 kHz and NXP has tiny tags for 50 cents that claim:    Fast Anticollision Protocol for inventory tracking: 100 Tags in 3.2 seconds  Hmmmm.

 

I'm talking to Chinese vendors on Alibaba for the obsolete Microchip DIP or SOIC chips that go with that App Note I found that covers all things RFID.  Since all my current RFID stuff is obsolete, I think I will stick with it.  That way it should all work together.  AM RF transmitters to program tags.  Something new for me.  A challenge.  A hobby.  Why not.  Just headaches, Jim.smiley

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It is interesting, the "programmable" tags I got years ago seem to have some anti-collision technology built in.  I dont know if the modern "programmable" tags allow you to program the ID number, or just the rest of the EEPROM memory on the tag for additional information.  My RFID reader is set up to scan and update an LCD screen with the tag ID number every three seconds.  If I hold up an old eBay tag next to a "programmable" tag and introduce it to my reader coil field the display alternates between the programmable tag number FFFFFFFFFF and the correct eBay tag number every 3 seconds.  If I hold the programmable tag next to one of the stronger cat tags I got with the cat door I bought years ago, my display seems to alternate between the FFFFFFFFFF and a mixture of the cat tag number and FFFFFFFFFF, so the displayed number ends in FF instead of the cat tag number ending 33, with a few more f's mixed in.  It is all pretty interesting.  I didn't know about this anti-collision technology.  Whenever I have held two tags close together in the reader field I would get nothing.  Now I get either one or the other or a mixture of the two depending on the tag next to the "Programmable" tags I got years ago.  It is all quite fascinating.

 

I am negotiating with some AliBaba vendors for obsolete Microchip MCRF200 and MCRF250 tag chips.  They are around $1.50 - $1.90 apiece.  The MCRF200 seems to be a one time write, and the MCRF250 seems to be writable multiple times with anti-collision technology, from my first scan through the data sheets.  All I can say is it looks like a fun project with obsolete parts for an obsolete person such as myself.  More later.