Anyone have any experience with custom antennas for the xNT implant?
  • JackalopiateJackalopiate November 2016
    So I'm working on wiring up an arduino Leonardo based board called Keyduino in order to unlock my car, however, I'm running into some issues. Most active NFC tag readers have a terrible read range with the xNT, due to its cylindrical antenna design, as opposed to the standard flat design that most readers use. My plan right now is to attempt to build my own antenna, matching the shape and roughly the size of the xNT in hopes that it will improve the readability. My problem is that I have no idea where to start on an undertaking like this. Can anyone with experience in NFC technology weigh in? The Keyduino has a UF.L connector, and all of the required components and logic to be able to read the signals and power the implant, all im looking for is the physical antenna itself. 
  • FredFred November 2016
    Yes. This still has a small read range, but is fairly consistent compared to a PCB antenna.
    http://www.dlpdesign.com/rf/fant.php
    https://0xfred.wordpress.com/2015/01/14/nfc-login-version-1-0/

    Here is my custom design also based on using an inductor.
    https://0xfred.wordpress.com/2016/03/04/nfc-login-2-1/
  • JackalopiateJackalopiate November 2016
    Awesome, thank you! I'll definitely be grabbing one of these and trying it out. what kind of range (mm) are you getting with it?
    EDIT:
    Also, do you have any suggestions on hooking this up to my Keyduino? I see you used a TI dev board (which I didnt know existed until today) But its like $200 for a piece of technology from like 2009.
     I'm pretty new to RF communication in general, and I'm not entirely sure what all goes into generating/reading signals.

  • njmbb8njmbb8 November 2016
    i don't know how much you like to read technological papers, but nxp has some great resources as does TI. This link seems good for the layperson, but i can't vouch for them
  • FredFred December 2016
    $200? The MSP430F5529 Launchpad is $12.99, came out in 2015. A great microcontroller for USB stuff. Far better than any arduino rubbish, proper JTAG debugging, etc. However you will need to actually code for microcontrollers rather than just download other people's "sketches".
  • JackalopiateJackalopiate December 2016
    Huh. Idk where the hell i was looking for it then. My project has evolved since the creation of this thread though, Ive decided to use a Teensy 3.5 as my controller, and im in the process of designing my own expansion board to connect the the DLP-FANT you recommended (which worked wonderfully with my keyduino). I'm using a PN532 chip for the NFC communication, and there dont seem to be any board that use it without including some big clunky onboard antenna for standard sized tags. Here is a link to a reddit post I made when i finished the schematic and didnt know if it would even work (Never made one before). I got in touch with the creator of the Keyduino and he said it was fine, with the addition of a debouncing capacitor on pin 24. Im currently working on laying out the pcb, but its slow going considering I don't have a bunch of money to drop on proto-boards, and I have never done this before.
  • JackalopiateJackalopiate December 2016
    Once its done, and I get a working version, I'll definitely be posting on here to see if anyone wants to chip in on a larger order, maybe have it pre-populated. I think that there would be great value in an NFC board designed specifically for xNT implantees.