Reading RFID cards - Schematics

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Bazzinga

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Greetings everyone,

I've been reading on RFID Technology and I'm trying to get a little more familiar with it by trying to read RFID tags. I'm going to use PIC16f877 controller. Now I've read about the Wiegnad26 format and I think I understand it. The RFID reader I bought (125kHz) has two lines (Data0 and Data1) for sending the card tag. So my question is how do I connect these to the controller so I can get (for example) the tag displayed on the LCD? I know how to display characters but I don't know how these lines so I can get the tag by means of USART.

Any suggestion or schematics is really appreciated
 

You can't read them directly, you have to use an RFID interface. The tags you have do not contain a battery, they are powered by the radio signal emitted by the RFID interface. Basically, when powered up, they modulate the power they draw to convey the data, the transmitter (connected to the PIC) senses the changes in load and converts it back to a bit pattern. You need the extra device to produce and monitor the RF power. Take a look at the data sheet for the HTRC110 for more details.

It is usually cheaper to buy a ready built RFID module if you are only building small quantities. For example: https://www.rfsolutions.co.uk/acatalog/RFID_Modules.html

Brian.
 

Actually, the reader I have (I think) is TTL compatible, so I probably can connect them directly to PIC's ports to read the incoming data, or am I wrong?
 

My own experience is with the first module in the link I gave. I use HITAG 1 tags, either in credit card format or as round discs.
My application uses an RS422 based network because it covers a wide distance using a simple PIC16F628A as the interface. The built-in UART sits on the RS422 link and I bit-bang a second UART to talk to the RFID interface. The same PIC also controls gate locks, an alarm, room lights, a doorbell push button and a sensor switch. So yes, it can be done quite easily. The 16F628A is very similar to the 877A it just has a few less pins.

Brian.
 

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