reader cloner

Description: The image below depicts a prototype combination card reader and cloner. This unit is self-contained, operating independently without the need for a PC or other external equipment. The operation is straightforward; the user simply needs to hold a card near the antenna for the unit to read and decode the card's information. The data is then formatted and displayed on a 4x20 character LCD. If the operator wishes to clone the card, they can bring a T5557/5567 Read/Write card near the antenna and press the "write" button. The LED will flash, and within less than a second, the R/W card is programmed with the information read from the original card, resulting in a cloned card. The estimated cost to build this device is minimal (approximately $30), which includes the LCD display and circuit board. The design is compact, fitting on a single-sided circuit board that was self-etched. The printed wiring board (PWB) was designed to match the size of the LCD, allowing them to be assembled as a single unit. The initial goal was to create a simple card reader capable of capturing all the information transmitted by the card during a read operation, as most commercial card readers do not output all data, such as the header and card format. This information is crucial for replicating a card's operation, prompting the development of a custom reader. An invaluable resource during this process was Microchip's 125 kHz RFID System Design Guide, available on their website. The FSK reference design circuit from this guide served as the foundation for the design, which was slightly modified to simplify the circuit and accommodate a Parallax SX28 microcontroller instead of a PIC. Upon reviewing the datasheet for the T5557/5567 IC (commonly used in access cards), it became evident that minor modifications to the reader circuit would enable it to also function as an RFID writer. The design required the ability to modulate the 125 kHz RF carrier using On/Off Keying (OOK) modulation, which is the programming method for T55x7 chips. The design was adapted to provide the microcontroller with control over the 125 kHz divide counter reset signal, and an additional push button was incorporated into an unused GPIO input on the microcontroller. A schematic of the modified reader circuit, now functioning as a writer, is illustrated below.

The prototype card reader and cloner is engineered to operate efficiently in a compact form factor, integrating essential components for both reading and writing RFID data. The heart of the device is the microcontroller, which manages the signal processing and control logic. The antenna captures the electromagnetic signals emitted by RFID cards, while the LCD provides real-time feedback to the user regarding the card data being read or written.

The circuit design incorporates a power supply that ensures stable operation of all components, including the microcontroller, LCD, and antenna. The use of a single-sided PCB not only simplifies the manufacturing process but also reduces the overall size of the assembly, making it portable and user-friendly.

The reader section of the circuit is designed to decode the unique identifiers and card format information transmitted by various RFID cards. This is achieved through careful tuning of the RF circuitry to ensure compatibility with the frequency specifications of the T5557/5567 chips. The modifications made to enable writing capabilities involve precise timing control of the RF modulation, allowing the microcontroller to send the correct signals to program the target R/W card.

In summary, this prototype combines innovative design with practical functionality, allowing users to read and clone RFID cards efficiently. The integration of a user interface via the LCD display and the simplicity of operation make this device a valuable tool for various RFID applications.The picture below is of my prototype combination card reader and cloner. The unit is self contained and does not require the use of a PC or other external equipment to operate. Operation is simple and straightforward. Simply hold a card near the antenna and the unit reads and decodes the information from the card. The information is then formatted and displayed on a 4x20 character LCD. If the operator wishes to make a copy of the card he simply brings a T5557/5567 Read/Write card near the antenna and presses the "write" button. The LED flashes and in less than a second the R/W card has been programmed with the information that was read from the original.

Voila ! - A clone card. The cost to build the device was minimal (approx. $30) including the LCD display and circuit board. The design fit on a single sided circuit board that I etched myself. The PWB was made to be the same size as the LCD so that they could be plugged together as a single assembly. I initially began this activity by trying to build a simple card reader that could be used to obtain all of the information that was transmitted by the card during a simple read operation.

Most commercial card readers do not output all of the data that is read. Information such as the header and card format are never transmitted as part of the readers normal output stream. Knowing this information is critical for being able to replicate a cards operation. As a result, I set out to build my own custom reader. A document that I found to be invaluable during my learning process was Microchip`s 125 Khz RFID Sysem Design Guide which can be found on their website.

RFID System Design Guide. Their FSK reference design circuit was basically what I used for my design. I made a couple of small modifications to simplify the design and to allow the use of a Parallax SX28 microcontroller instead of the PIC. After studying the datasheet for the T5557/5567 IC (used in many vendors access cards), I soon realized that the reader circuit would only have to be modified slightly in order to also be able to function as an RFID writer.

To function as a writer the design simply needed to be able to modulate the 125Khz RF carrier using On/Off Keying (OOK) modulation since this is how the T55x7 chips are programmed. I modified the design to accomplish this by basically giving the microcontroller the ability to control the 125 Khz divide counter reset signal.

An extra push button was also added to an unused GPIO input on the microcontroller. A schematic of my reader circuit (modified to become a writer) is shown below: