AVR RFID, Optimized and Ported to C

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Way back in 2008, I posted a writeup about using an AVR microcontroller as an RFID tag. Since then, it’s been great to see many people pick up this code and build their own DIY RFID tags. In my original project, I was just interested in using an AVR as a way of emulating any tag protocol I wanted, even proprietary protocols like the HID cards that are so common for door entry.... Read More

Duct tape RFID tag #1

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This is just a messy first prototype, but I recently tried making an AVRFID tag on a substrate of duct tape. The first attempt involved: An upside-down strip of duct tape, as the base for everything else to stick atop 100 turns of AWG 40 magnet wire around a ~66mm diameter form, which I then haphazardly squished against the tape An ATtiny85 µC in the SOIC-8 package, programmed... Read More

AVRFID 1.1 Firmware

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I don’t normally write bloggy posts on every version of every source file I check in, but every so often an older project sees some more activity, and I love the opportunity to revisit software I wrote years ago. Sometimes I wonder why I wrote such-and-such thing that way and oh my god what an ugly hack. But usually it’s just refreshing to think about a problem I haven’t... Read More

Soft RFID tags and cuddly plushies

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This week a new power tool arrived on my desk: How did this happen? It was actually kind of complicated… Months ago, Scott and I dreamed of an automated kegerator. For the workplace, naturally. We’d need some way to hand out credits that coworkers could use in order to dispense beer, so we’d need a way to identify people or otherwise store these credits. We could... Read More

Using an AVR as an RFID tag

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Experiments in RFID, continued… Last time, I posted an ultra-simple “from scratch” RFID reader, which uses no application-specific components: just a Propeller microcontroller and a few passive components. This time, I tried the opposite: building an RFID tag using no application-specific parts. Well, my solution is full of dirty tricks, but the results aren’t... Read More

RFID Garage Door Opener

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Today I finished a major update to my software-only RFID decoder for the Propeller microcontroller, and I finally installed my prototype in the garage. Now I can open the garage door with my RFID badge from work, while I’m on foot or on my bike I’ll post some pictures once there’s some sunlight. (Edit: Took some pictures this morning)  Read More

Simplest RFID reader?

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That’s a Propeller microcontroller board with a few resistors and capacitors on it. Just add a coil of wire, and you have an RFID reader. Here’s a picture of it scanning my corporate ID badge, and displaying the badge’s 512 bits of content on a portable TV screen: If you’re into that sort of thing, I wrote a forum post with technical details and pretty... Read More