Archives for category: Moderation
  1. 21. September 2008: Using an AVR as an RFID tag by Author Beth (Micah Dowty) and version 1.0 of the avrfid.S . Also found as the Emulator RFID.
  2. 15. June 2010: AVRFID 1.1 Firmware by Author Beth (Micah Dowty) version 1.1 of the avrfid.S which incoporates a few patches by Luke Koops who improved the FSK modulation for HID tags, so that the resulting waveform is much more regular and Cesar Fernandez who described the HID card format in more detail.
  3. 16. May 2011: Duct Taped AVRFID by Author Beth (Micah Dowty) uses her version 1.1 avrfid.S
  4. November 2011: AVRFID PCB Implementation by Daniel Smith
  5. September 2012: RFID Spoofing by Eric Barch who only uses Beth’s (Micah Dowty)  HID part of her version 1.1 avrfid.S .
  6. 1. December 2012: AVRFID 1.2 Firmware last update by Daniel Smith on his version 1.2 of Beth’s avrfid.S which adds support for 35 bit HID Corporate 1000 format and fixed 26 bit parity.
  7. 27. December 2012: AVR RFID Multipass by Trammell Hudson of the NYC Resistor hacker collective, which come up with an optimized version of Beth’s version 1.2 avrfid.S and convert it to C ending in the avrfid2.c file. Beth (Micah Dowty) welcomes this transition as it uses less of the 8kB flash memory of the AVRs etc… and has an nice application scenario of an action figure, whose body parts trigger different IDs in the AVRFID tag. The whole code in C for latest AVRFID tag and the reader can be found here. In his post Hudson also describes how easy it is to reprogramm AVRs with some Bus Pirate Tools, which provide an recovery clock. But a few patches are still needed!

The goal is to have a RFID interaction Processing library in the end, which helps for rapid prototyping of RFID interactions:

Maybe I can even realize an integration with the simple visual programming language Scratch.

I have spent quite some time to get the serial communication between Processing and Arduino working. Unfortunately I haven’t succeeded yet. It’s either some vagabonding libraries or a 64bit incompatibility issue. The only information according this error was in the Processing wiki and in a messageboard thread. They recommend to manually replace some jars and dlls, but their troubleshootings didn’t work yet. I still have to try another specially 64bit compiled version of the RXTX library. I watched thru several serial communication tutorials (1,2,3,4,5), hoping to find some more informations according this error. I also stumbled over the CmdMessenger Library, which sounds like a interessting solution for the serial communication (CmdMessenger on GitHub). I also got the Eclipse plugin for Processing, but the same here. Right now I don’t know, if I should just put a fresh Windows version on my pc or if I should keep on trying to solve that error elsewise! So for the moment, I stepped back to the Arduino Code which already worked but hasn’t had the perfect formatting of the IDs in decimal.

I tried to get the formatting of the hex ID data right, but I was quickly confronted with the limitations of the arduino microcontroller chip. Having a good debugging with a lot of strings and implementing the ASCII table as an array, was to much for the 2 KB RAM of the Arduino Uno. Now I have installed Simple Digital Firmata and will do the debugging and formatting computation in processing. More to come…

In order to use the ATtiny85 as a RFID chip, I first need to wire up a new RFID Reader module. The reason is that the operating frequency in this setup is going to be 125kHz and not 13,56MHz like in the previous paper RFID examples.

Quick overview of my temporary and yet to the end a little rough thesis structure:


The paper RFID tags, were the first tests with the 13,56MHz preprogrammed RFID chips. During the next step I will experiment with the Amtel AVR microcontroller chip ATtiny85. First of all I will have to install different things and get the Eclipse IDE updated for programming AVRs. Then I will wire up a small docking station to programm the ATtiny85s with the Pocket AVR Programmer by Sparkfun. Good overview about AVR programmers can be found here.

Before I will build some more paper RFID tags, I need a RFID reader to test the new tags. So I got the SM130 13.56 MHz RFID Mifare Read / Write Module with the according antenna.

Welcome to the Blog Tesla User Interfaces! It will document the work on my diploma thesis and will give a detailed sight on the RFID technology and ways of interaction.