Choosing the Right RFID Card Technology For Your Embedded System

Altium Designer
|  Created: May 11, 2018  |  Updated: December 9, 2020

 application of RFID cards

As a pure introvert who fears small talk, I absolutely dread networking events. Besides maintaining endless empty chatter with strangers, picking out the best attire is challenging, especially considering my dreadful fashion sense. Thankfully, I’m much better at choosing the right type of Radio Frequency Identification or RFID card technology for my embedded system projects.

What is an RFID Card?

In the simplest sense, an RFID card is a token that relays identification information using radio wave transmission. An RFID system involves an RFID reader and multiple tokens. These tokens are usually shaped like cards, coins, or a RFID tag. The most primitive type of RFID system only allows you to read of the identification value hardcoded into the RFID card. The simplest RFID cards contain an RF antenna and a non-volatile memory, which stores a unique ID. It derives power from the radiofrequency wave emitted by the reader and allows the reader to retrieve the identification value.

Higher-end RFID cards are significantly more complicated, compared to the simple ones. Instead of merely having a memory, high-end RFID cards have an embedded microcontroller that can perform a complicated authentication routine and implement encryption to prevent unauthorized access to card’s contents. These advanced RFID cards typically have sectors of memory that can be written by the reader device.

You’ll find that RFID cards are commonly used in access control, ticketing system and contactless payment cards. They do not require line of sight reading like barcodes. They also avoid risking data corruption like magnetic cards do.

Popular RFID Technology

Unlike your vast wardrobe selection (which suddenly becomes insufficient when you have to attend a dreaded networking event), RFID cards are limited to a few types of standards. The popular ones can be boiled down to Mifare Desfire, Mifare Classic, and the 125 KHz proximity card. The 125 KHz card is a simple RFID card that allows reading of its ID when powered by radiofrequency waves.

The Mifare Classic is a significantly advanced RFID card that allows reading the card number and enables writing in certain sectors of the card. It supports encryption for the communication between the card and the reader over a 13.56 Mhz frequency. It was deemed a more secure RFID solution than the 125 KHz card.

However, Mifare classic dealt with its own drawbacks when a security flaw was discovered that could lead to the card potentially being cloned with identical values. To avoid this catastrophe, the Desfire standard was introduced. With the implementation of Triple DES encryption of the transacted data, the Desfire cards feature improved security.

Under the layer look at RFID cards

Sneak peak of the internal workings of an RFID card.

How to Choose the Right RFID Card

Choosing the best RFID card for your needs is an important decision. Making the wrong choice means a chain effect of repercussions from to end users. To save you from picking the wrong RFID card, here are a few questions to ask:

1. Do you need to write on the RFID card?

In some applications like a simple access control system, a simple verification of the RFID card number is enough to authenticate a user, based on the database stored on the server. In this case, 125 KHz cards can be good enough. Otherwise, the Mifare Classic is perfect for storing customer information in loyalty card applications.

2. Are they used for payment cards?

RFID cards are popularly utilized in payment cards. Instead of cash, the RFID card contains an equivalent amount of money that is securely stored. Payment is made by presenting the cards to designated readers which deduct the transacted amount accordingly.

This delicate process requires a higher level of security to prevent malicious hacking of the card. The Mifare classic was a popular choice for payment cards until Desfire was introduced with superior security features.

Keep the money safe, always

Payment cards demand the strongest RFID security.

3. What’s the Minimum Reading Distance?

If you need a reasonable reading distance, for example, for a token of vehicle parking system, a 125 kHz will offer better range than a Mifare smart card. In such cases, building a database around a card ID or credit card is better than using Mifare cards. Besides, this makes it unnecessary to pay more for Mifare cards, which are more expensive than the 125 kHz cards.

Integrating RFID Cards With RFID Readers

Regardless of your choice, you need the right RFID reader to read or write on cards. It’s unlikely that you will design the readers themselves unless your job specifically revolves around designing RFID readers. Most designers would need to spend time searching for the right RFID readers.

While you’re not designing a RFID antenna, you still need to maintain a high standard of design for your card’s communication with a reader. Most RFID readers allow for serial communication while only some support a USB interface.

In either case, comprehensive PCB designer software like Altium Designer® is handy in efficiently routing communication lines and implementing clearance rules to minimize interference.

Still unsure about the right RFID card for your embedded system? Talk to our experts at Altium.

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PCB Design Tools for Electronics Design and DFM. Information for EDA Leaders.

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