[Fabien] ran across a very, very inexpensive RFID reader on Deal Extreme a while ago and with money to burn, added it to his cart. When the USB RFID reader arrived, he noticed something fairly odd about it (French, Traduction). The RFID reader presented itself to his computer as a USB HID device that spit out characters into a text editor whenever an RFID card was waved above the coil. The only problem was these characters weren’t the hex values recorded on the RFID card. So what’s going on here?
As it turns out (Anglais), this random piece of Chinese electronica sends 10 bytes of data to the computer, just like this well-documented RFID reader. Apparently, both these RFID readers take the hex value of an RFID card, convert those bytes to base 10, and pass each digit through a lookup table. Exactly why it does this is anyone’s guess, but since [Fabien] figured out how it worked, he could also figure out how to reverse the process.
Unfortunately, the RFID reader in question is currently out of stock at Deal Extreme. Seeing as how most of the electronics available there are remarkably similar and differ only in the name printed on the enclosure, though, we wouldn’t be surprised if a nearly identical RFID reader was available elsewhere.