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Issue #211 February 2008
RFID Payment Terminal
by Carlos Cossio
Carlos’s LM3S811-based handheld terminal makes contactless payments a reality. The terminal’s LCD—which shows the date and time—prompts you to enter payment amounts on the keypad. After transactions are complete, the log file stored on the device’s flash memory can be sent to a host system through an RS-232 interface.
Start | System Overview | Energy Transmission | 100% Amplitude Modulation | Load Modulation | MIFARE Card | MIFARE and ISO 14443 | Pay as You Go | Hardware Design | Antenna Design Rules | Antenna Size | Directly Matched Antenna | Firmware Design | Catch the Wave! | Sources & PDF
When I first saw a contactless card in action, it seemed like magic. A single piece of plastic with no battery inside was able to exchange information back and forth in a nearby terminal with the help of just a coil antenna. It was amazing!
I later discovered that the contactless card was part of a technology called RFID. You may know that RFID technology, which is changing the world of tracking and logistics, will soon replace the old-fashioned barcode technology that has been in use for more than 30 years. However, the RFID contactless card is one step ahead when compared with RFID memory tags. It has all of the functionality and security offered by the smart card but without the contact interface. That’s why it is called a contactless card.
Even though RFID technology was originally intended for the tracking and logistics markets, they are not the only places where this promising technology can be used. Thousands of contactless readers are quickly appearing in stores, restaurants, and other merchant locations throughout the world to enable contactless payment, replacing the old magnetic stripe cards (e.g., the successful PayPass card from MasterCard). This technology is also used in transit systems to enable fast and convenient travel for commuters. It is also used as a ticket for transport applications issued by public transit operators in major cities around the world (e.g., the Oyster card in London). In order to support such applications, financial institutions and transit operators are issuing millions of contactless cards and key fobs. Some governments are planning to distribute millions of ePassports and national ID cards equipped with contactless chips and antennas, and many corporations are already issuing contactless cards and badges to employees to control building access.
My project showcases the design of a contactless handheld terminal to demonstrate the use of RFID technology for contactless payment. The design (I call it “MoneyPenny”), which is built around a Luminary Micro Stellaris LM3S811 microcontroller, implements an electronic purse (e-purse) application for an NXP Semiconductors MIFARE contactless card with an operating distance of up to 10 cm (see Photo 1).
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| Photo 1—This is the RFID payment terminal at work. Just enter the desired amount and pass a Mifare card in the vicinity of the terminal to start the contactless transaction. |
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