notANON

Thanks to a hot tip from Hack a Day, I became the proud owner of a RFID reader for $10.  It is a Parallax branded part.  If you go to Radio Shack, you’ll probably find that it’s not marked down in the drawer but when you take it up to the cashier, it should ring up at $10. In the past, I’ve always disregarded the Parallax branded parts because I associated them with BASIC stamps which I am not to interested in since I feel like they are excessively priced considering an AVR can do all of the same stuff and more with a little fiddling.  Taking a closer look however, I see now that most of the accessories could be interfaced with any project.

On the front of the package, it has the RS part number which is 276-0032.  It is labeled “RFID Reader with tags”.  Below that it says:

• 2400-baud serial output
• Easy prototyping and integration
• Includes two passive ransponder tags (yes it there is a typo on my package)

On the back side of the package it says:

• Ideal for payment systems, inventory tracking and similar applications
• 2400-baud serial output to a PC or other processor
• 0.100 pin spacing for easy prototyping and integration
• Includes 2 different passive transponder tags
• Dual-color LEDs

Whatever the case, I opened up the package and found the reader and the two different RFID tags.  One is a donut-shaped ring that says “World Tag Unique RFID – Logistic and Industrial Transponder“.  The other tag is unmarked but appears to be a blank ID card that is ready to be printed.  I couldn’t find much info on that World Tag and there is even less on the blank card since it’s not labeled.  The only sensible thing to day here is to test it out and see what happens!

With a little help from the RFID Reader #28140 datasheet, I found that the ENABLE pin needed to be grounded to activate the antenna.  When you apply power, the LED turns green, then you ground the ENABLE pin and the light turns red.  This means the unit is ready to scan RFIDs.  I used a prolific USB-Serial adapter and booted hyperterm in a VM to capture the output of the device. I plugged a null modem cable into my serial converter so it would be easier to jumper down to my breadboard.  I wired pin 3 on the null modem cable to SOUT and pin 5 to GND.

The “numbers” that the device spits out seem to be a 12-byte ascii string of somewhat odd characters so what I get in HyperTerminal isn’t especially readable.  I did copy and paste the output into a hex editor though and it became a bit more coherent.  Reading the datasheet mentions that the first and last byte are start and stop bytes so that leaves you with 10 actual bytes of unique identifier string.  This works out to a WAY larger number of possibilities than I can comprehend(1.16252367 × 10 to the 24th to be precise).  A couple of interesting facts…  As long as I hold the card near the reader, it continues to spit out it’s string over and over.  When I pulled the tag away quickly, sometimes I’d only get a partial read but then it would usually start again at the beginning when I would put it back again.  Putting two tags near the reader at the same time seems to confuse it as I would expect.  It does fairly well in that regard though.

One thing to note is that I ran into some serious reliability issues as the voltage of my dying batteries dropped.  When they got down to three volts, the reader failed to function even though the indicator light was still bright as ever.  Plugging it into a wallwart did the trick though.

This is a bare bones reader.  What I mean is that ALL it does is read the tag and spit out the number over and over again.  It is up to whatever you plug it into to give the user tactical feedback of some nature that the card has properly been read.  IE, this reader doesn’t beep, blink, buzz etc, so they leave that part up to you.  There is also no inherent security in this device to speak of.  If someone could tap the serial line, they could obviously spoof whatever number can be read.  As far as cloning the tags, I’m not sure how it could be done but I’m sure it’s possible.  I DID try to scan various different tags I could find in my house with no success.  First one was an HID card.  I didn’t expect anything but it was worth a shot.  Also tried the rest of the cards in my wallet with no success (thankfully) and a few various inventory control tags.

Personally, for my own projects, this is a solution without a problem but these RFID tags are everywhere so it is an interesting study to see how they operate on some level.  If you want more information on this RFID reader, the datasheet is an excellent resource.  Extra RFID tags are available in low quantities from the Parallax store