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This idea fully exploits the configurable logic aspect of the 74aup2g57gm. This idea work similarly to AES encryption. Each configurable logic device would be act as a tumbler preceding the logic device before it. The opens and shorts would determine the resulting logic which would result in an unique code for that message. To further encrypt a GPS Time sync could be added to allow for a more obscure message. To decrypt the device would simply need to be inverted…so a message could be uniquely encoded using a basic ASCII binary representation. The hardware device would be the key for the message. so something like this could be realized. There’s probably a patent lurking somewhere within this one…. 🙂
USB -> NXP Encryption -> Computer
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Looking at the data

the complete schematic is here:

Schematic for RFID1 simulation


Input and output for RFID1. It may be desirable to increase the DC offset or the amplitude of the output
But i’m going to go with this signal to start and work on refining the output after I breadboard the design.

So there are a few ways to increase the strength of the output signal while still maintaining the necessary modulation of the RFID card. I added a small load on the output. This did reduce the over all time the signal was ‘high’ but it would likely not matter much to the micro-controller.  I increased and decreased the overall inductance and changed the ratios of a few resistors but mostly it led to an instability in the overall output of the signal.  Coilcraft has a few nice 125 kHz RFID inductors on their site that I’m going to add to the BOM and the board layout.

My next step is to work on doing the PCB layout, routing, stack-up, geometry ect and get the board made. Then I’m going to build up and test a breadboard while I wait for the real parts to get in. I’m not going to buy a micro controller yet…I have an arduino device in mind but I’ll post another section on this hardware.


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building the RFID schematic

Well I spent most of the night building the schematic for the RFID transmitter. Reverse engineering is always difficult at first but it is important and useful to build from. Today was also cool because I was able to go through my Time Robot’s magazine. This definitely gave me a few ideas of how and what to build in the future. 🙂

I ran into a few issues tonight. My VMware machine stopped working. I had to go into the program folder and delete the files ending in .Ick. After I did that I was free to work with the VM. There is some risk to the VM not being recoverable but I’m uploading all my files to the shared drive.

I also found a few datasheets to give an idea of what the circuit is doing and uploaded them as well. So after debugging here is my progress:

So after I complete the schematic I’ll go through the analysis for the analog and digital signals and see if we can improve this design at all 🙂