2015-07-21 (Tu) RFID Authenticator

Hardware was breadboarded for reading 125kHz RFID tags. A reader was purchased long ago which reads the RFID tags and sends the serial number over serial communication. Data is transmitted at a constant rate, 9600bits / sec, and followed by a newline ('/n') symbol. One advantage of this unit and similar units is that they use an external antenna. External antennas means that making a loop of magnet wire is all that is necessary for creating a custom antenna so they can be custom built. Units with circuit boards and printed antennas are limited or would have to be modified. Custom antennas can be altered with so ones with greater range or pass through capabilities could be tested.

The first attempt was to hook up the serial ports of an Arduino and the RFID reader in parallel but this failed. When the SoftwareSerial library was installed there was no success with and Arduino Mini Pro until the reader's transmit (Tx) pin was moved to pins 2 which allows interrupts. A simple data relay was implemented from the SoftwareSerial example to display data from the emulated serial port onto the Arduino's normal serial port on pins 0 and 1. In other words a couple of the Arduinos pins were used like a serial port and the Arduino talked to the computer through its usual serial port. Baud rate was changed on the Arduino to prove the SoftwareSerial data from the reader was completely isolated from the Arduino, which it was.

Breadboard of reader and Arduino

Video was shot which showed a simple program which held the Arduino's onboard LED high whenever a tag was being read. This was to prove the Arduino could recognize when data was coming across the emulated serial port. While reading RFID tags the computer was able to monitor the tag being read and see the serial number of the tag. No screen shot was provided since sensitive data was being read. Programming progressed to have a tag's serial number hard-coded which alone could trigger the light on the Arduino, other tags could not trigger like they could in previous versions.

Program which keeps the light high when any tag is present

Master tag version which only recognizes a particular tag

RFID Authenticator Arduino Code

To do:

  • Make code public
  • Define necessities of code
    • Act like commercial version
      • Acknowledge master tag
      • Allow new tags to be recognized after scanning master key
      • Store new tags in EEPROM memory. Non-volatile
      • Pin goes high only when recognized tag in place
    • Different pin goes high when unrecognized tag is scanned (tampered)
    • VERY first tag scanned becomes master tag
  • Make linkable list of parts

The rest of the posts for this project have been arranged by date.

First time here?

Completed projects from year 1.
Completed projects from year 2

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2015-07-17_02 (F)


  1. The RFID Authenticator Arduino Code is not there :( dropbox not found

    1. Hello Anon, I fixed the links for the code. You shouldn't have trouble downloading anymore.


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