Simple RFID reading circuit, and simple RFID code?

Information is quite limited on RFID. Anyone have experience?

Cabe

I don't know how many of your circuits you are planning - if not so many, you might consider a module / modem which allows you to connect e.g. a serial interface and power and you are finished with RFID integration. You can find such modules under e.g. www.metratec.com (this is also my employer so I guess I like their modules... Documentation is available there) but there are also others who offer modules. Basically, the modules save you from having to do real HF engineering.

If you want to do it yourself, all reader ICs I know have App notes including circuit suggestions - these are valid starting points and will get you a working solution even though with less performance and with a lot more work than the better modules.

NXP has some tag ICs in solderable packages - these can easily be put on an according antenna. Designing the antenna does require some HF knowledge, though. This might be a challenge or just routine for some of the experts.

I was quite impressed with this guy's minimalistic aproach to RFID reader and especially his RFID tag.

http://scanlime.org/2008/08/simplest-rfid-reader/

http://scanlime.org/2008/09/using-an-avr-as-an-rfid-tag/

He used Propeler mcu, but it shouldn't be too difficult to port it to another platfom.

Cool hack but with the obvious drawbacks - 125 kHz system only, probably too much spurious emissions for any real (legal) usage. Tag is cool but again 125 kHz.

I know that someone - I think it was Schneider Electric - once did a 13.56 MHz tag based on a low-power MCU years ago and could read it at 30 cm (if I recall correctly). The good thing about a MCU-based tag is that you can potentially connect any type of sensor to it and even power it from the field.

I know a very good and reasonable cheap RFID system on 13,56Mhz.

You buy the MLX90121 of manufacturer Melexis and construct the reader with the application notes provided by this chip. (limited ammount of hardware)
You connect this reader to a microcontroller to control the reader en to send the UID that you read from the tag via any form of communication to a PC.
The tags are cheap and provide enormous posibilities to write extra data in the memmory of the tags. (I prefer 13.56MHz tags from Texas Instruments)

You can also buy the evaluarion or development board that uses this specific RFID chip.

@Franklin: the MLX is a nice IC but as with all RFID protocol ICs I know (which is quite a few) the reference designs delivered with it only get you so far - but the result does work (we have improved on it significantly, though...). Better read range and easier integration is available using good quality modules.

Indeed with a good design you can improve the quality significantly. Some points that are very important are

• Antenna (material used, matching network, size, form (flat PCB or tube or ...)
  
• Reader PCB and casing (interference between signal lines, connection between reader PCB and antenna, ...
  
• Controller hard- and software
  

@metraTec : I just visited the website of your company and indeed the RFID systems specs are high performance systems.particlary the lambda40 antenne is amazing. 

The AS IC has some cool features but we haven't found time to test it yet.

The predecessor of the TRF7970 was well suited for boosting the power level to 1W and reading at up to 40cm - again, we haven't had the time to test whether this still works.

The MLX works at more that 100 tags / s and at over 25cm read range for an A4-size antenna under good conditions if designed well (unboosted!).

Thank you all for the replies. I think the example project is a great place to start with RFID.

As for my application, I wanted the tag and readers to fit into a very small place which still having a read distance of 1-3 meters.

Thoughts?

Cabe