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Issue #211 February 2008
RFID Payment Terminal
by Carlos Cossio
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
SYSTEM OVERVIEW
My RFID payment terminal has an LCD to show the current date and time and prompt you to enter your desired payment amount. It also has a numeric keypad for entering data, such as the payment amount, and setting up several parameters of the terminal. Additionally, thanks to the built-in real-time clock (RTC) and flash memory, you can keep a log file of all the transactions performed by the terminal with a time and date stamp for all approved transactions. Upon request, the log file can be sent to a host system through an RS-232 interface for further storage and analysis.
I implemented the contactless interface with the help of an NXP Semiconductors MF RC531 ISO 14443 reader IC for the modulation and demodulation of the contactless signals at 13.56 MHz. Additionally, the contactless terminal has an innovative built-in antenna under the keypad to enable portable operation right out of the box without plugging in an external antenna.
The following is a brief introduction to the principles of contactless technology, which will help you understand how the device works.
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