Parallax RFID Module Help

So I picked up a Parallax RFID module for a project and excitedly plugged it in and loaded up the code from and I get nothing. I'm really disapointed and I've played around with it a lot but it just dosn't seem like the RX pin is getting any data from the reader. Has anyone been able to get this working and if so can you give me any suggestions as to what is wrong or how I might check it? I'm also a bit affraid that I may have damaged my arduino board playing with anouther project and this is why it's not working.


I wrote that tutorial, therefore it should work fine. Let's see...

OOPS, I seem to have made a mistake. I left out the fact that you need a four-wire connection: connect the Arduino +5 to RFID VCC.


PS: i just looked at the code and discovered something that could have been the probelm: digitalWrite(2, LOW); // Activate the RFID reader was set to work on pin0! Fixed. Try the code in the Playground now.

I hooked up the 5v too and still didn’t work, I got a TTL to USB cable and hooked up the reader to that and it worked fine. Let me try the code now though.

That fixed it. Thank you so much. I have programming experience but I'm new to C and Micros so that slip would have taken me forever to find and I already tried a bunch of other things.


that's great. Looks like I assigned pin 2 to be the enable pin for the RFID at the time, but never called it in the code. It must have been floating enough in the right state at the time to make it work, or I might have just had it tied to ground and not noticed its relationship to the code.


Real quick the code to Deactivate the reader after reading the tag is still set to the wrong pin.

digitalWrite(0, HIGH); // deactivate RFID reader

Shold be pin 2 instead of 0.

thanks, fixed. This is why I am a 'hardware person' and not a 'software person'.

The Playground is a wiki, so if you sign up for a password ( the process is automatic), you can correct these things too!


i’ve recently received a parallax RFID reader and followed the connections and code described. Unfortunately, the only way i can get it to report the RFID tag is when i reset the Arduino. At that point the tag code is displayed in the terminal (without the accompanying text).

Thoughts? Any help is greatly appreciated.

We'd need to see what code you are using on your Arduino.

The module is:

$40 from original supplier (i.e. not waiting for eBay bargains)


  • Low-cost method for reading passive RFID EM4100 family transponder tags
  • 2400 baud serial interface

Compatible tags:

  • 54x85mm Rectangle Tag ISO Card: 6.3cm (2.5") +/- 10%
  • 50mm Round Tag World Tag 50mm: 6.8cm (2.7") +/- 10%
  • Blue Eye Key Fob
  • 25mm Disk Tag

Vcc: 5v, power needed not stated.

=== The Phidgets unit communicates over USB, and relies on a big proprietory .dll... probably not suitable for Arduinos, but see separate thread for that one.

Picked up 2 of these for $10 each at RadioShack saturday. They're being discontinued or somesuch.