AVR/Arduino RFID Reader with UART Code in C

RFID is the craze, found everywhere - from inventory systems to badge ID systems. If you've ever been to a department store and walked through those metal-detector-looking things at the entrace/exit points, then you've seen RFID.

There are several places to find good information on setting up RFID, and this instructable focuses on installing the Parallax RFID reader (Serial TTL) on an AVR, with emphasis on the C code needed to read the serial input.

The code is in C and doesn't use any external libraries. In fact, it speaks 2400 baud directly without the use of a UART by synchronizing to the RFID reader's baud rate and reading the digital pin that it's connected to. Excited? Me too.

Step 1 Get the Goods

You'll need the following list of parts:

• RFID Reader (Parallax #28140 $39.99)
• RFID tag ( Parallax #32397 $0.99)
• AVR or Arduino clone (if you use a stock AVR, you'll also need a max232, 5 x 1uF capacitors, and a DE9 connector)
• Solderless breadboard

Optional

• 4 position header
• Wire

(and the max232 etc for communication of the tag information)
You could also connect your favorite LCD screen in lieu of sending tag data via RS232.

Comments

[Catch_22_]

Although it's only available in-store only, I got this exact parallax model for 8.95 at my local RadioShack. Much much better then paying $30+ along with shipping.

[apburner]

I did the same. I already had one but at 9bucks I could not pass it up

[nevdull]

Yeah, that's an unbeatable price. My RadioShack is soooo overpriced.... I favored the serial over the other models, besides for the price. Seems more flexible.

[nate4alpha]

Does anyone have the complete code to get this project to functioning properly?

[nevdull]

Ever since they changed the policy in allowing non-pro members to have formatting, most of my pages started looking bad because of the lack of formatting (I include a lot of code).    Page 4 should have a downloadable zip file for the code.

[scottyb4996]

I downloaded the ZIP File. How do I load it into the Arduino IDE to get it to function properly?

[nevdull]

It's written more in straight C than in C++ for the Arduino IDE. It works on an Arduino, but I don't use the Arduino IDE so I can't offer suggestions on how to import it into that environment. Good luck!

[nate4alpha]

What's the name of the white board on this page?

[nevdull]

If you mean the circuit board with the ATMega chip on it (it's white, the chip is long and black), then it's called the Bare Bones Board and can be found here:  Modern Devices
I recommend them highly, as well as buying the USBub USB to USART converter pictured to the left.  It makes communicating via serial RS232 soooo easy.

Good luck!

[nate4alpha]

Thanks for the help!

[jeff-o]

Very cool. So what types of RFID tags can it read? Security badges? product tags?

[nevdull]

I did draw up initial plans when I first got the RFID reader to install it, along with a couple of motors and an AVR MCU, into a hand scanner that I had lying about, but with the dismal range I think anything I wanted to scan would have to just about be laying on it. Ah, grand hopes and best intentions dashed on the rocks of sober reality. I have been thinking that I might still reincarnate that hand scanner into something, yet, since I have two ultrasonic transceivers that are just dying to go into a fresnel lens to do 360 degree sonar scans. I'll have to see about that...lol.

[nevdull]

Hey Jeff!
This reader can interrogate any passive 125 kHz transponder tag, which is in the low frequency range, as far as RFID tags these days go. Industrial-strength RFID is often in the 13.56 MHz and 868/928MHz bands, although there are some microwave tags and readers in the ~3 and ~6 GHz range. With it's 10-byte ID, it offers 2^{40 unique combinations.}

So far, the only tags I've read are the one's I've purchased to put on my dog and cat (it's a long story, really) and the range of detection is underwhelming (~ 4cm although the claim is closer to 10cm) although increasing current can increase the antenna's inductance, up to a point. If I could find some RFID tags from some books I'd try those to see if they might work. I use a magnetic card to get into my lab, but my brother uses an RFID badge system, so maybe I'll snag his belt fob and see if I can read that. I'd be more excited if I could *write* to them as well as read them. That would open up some interesting possibilities next to my magnetic card reader... ;)

[jeff-o]

Indeed it would! Some legit, some not so much... ;)