This week’s EYE ON NPI is neither-here-nor-there – it’s STMicroelectronics’ ST25R200 NFC/HF RFID Reader IC, a simple but powerful NFC/RFID reader and writer chip that will let you add a contactless interface to your next design.

Thanks to the high power RF stage and dual antenna support, you can avoid the frustration of “where do I tap??” by giving you plenty of surface area for successful transactions.

We’re big fans of intuitive RFID/NFC interfaces using tags, they come in all sorts of sizes and shapes from standard business cards to microtags that can fit in a manicure. They don’t require a battery, and can store up to a few KB of data, including encrypted/secured data sections so as to make the tag ‘trustworthy’. They’re often used for small-money transactions like copy shops, laundromats and public transport, where speed is important and we can store value on the card. Or for identification like access cards. With proper design, they’ll work up to 4 inches away from a reader, don’t suffer from corrosion or contact wear or affected by water/humidity.

Reading and writing RFID/NFC tags, which use 13.56MHz as a carrier frequency, requires a proper chip that can handle the requirements of blasting enough RF signal to ‘power’ the tag, then transmit a command and receive the response before the quiescent power runs out. If you have a big antenna, this isn’t too hard – but the real challenge is to manage it with a small antenna.

That’s the nice thing about the ST25R200 – it has powerful output drivers so even mini wearable-sized antennas work well. You can configure the outputs to be one differential or two single-ended antenna coils.

If you want to design your PCB antenna, we recommend ST’s website for NFC inductance calculations – it will let you determine the inductance based on width, height, copper thickness and trace width so you get maximum power transfer.

The ST25R200’s connection to the controller is over standard 4-pin SPI, so you can use any microcontroller or microcomputer with 4 pins available. An IRQ line is also handy to ‘wake on card detect’.

Other than that, the interface is fairly low level: registers are used to configure the RF section and encoding but otherwise, data is transmitted or received via two FIFO buffers. This makes the chip easy to adapt to the various sub-protocols and standards designed by competing RFID companies: ISFO14443A/NFC-A, ISO14443B/NFC-B, ISO15693/NFC-V, NFC Forum T1T, T2T, T4T, and T5T tag types, and proprietary protocols, such as Kovio, CTS, and B’.

In order to make your life easier when it comes to implementation, ST has released RFAL, an RF/NFC abstraction layer that is written in pure C, so that it can be ported to any platform or compiler.

To get started quickly, we recommend the STEVAL-25R200SA evaluation board which comes with a USB debug STLink interface, SMTable module, 4 pluggable antenna options including one flex PCB printed antenna, and two micro-tags for testing.

If you want to integrate RFID/NFC ‘touchless’ support to your next design, the ST ST25R200 NFC/HF RFID Reader IC is small, inexpensive, and fast to get started with minimal external components, and ready-to-go drivers. And best of all, the chips are in stock right now at DigiKey for immediate shipment. Order the ST25R200 and an eval board today and you can tap your way to contactless communication by tomorrow afternoon!

See the video below and the manufacturer’s video on the eval board: