Technical Article. NFiC: a new, economical way to make a device NFC-compliant. Prashant Dekate

Transcription

1 Technical NFiC: a new, economical way to make a device NFC-compliant Prashant Dekate

2 NFiC: a new, economical way to make a device NFC-compliant Prashant Dekate The installed base of devices with Near Field Communication (NFC) technology is increasing exponentially it is set to become a standard feature of many smartphones on the market in the next 18 months. This now provides an opportunity for manufacturers of almost any other kind of electronic device to improve the user experience by enabling the user to easily connect their product to a smartphone wirelessly via NFC. The question for system designers, however, is: how to do this in practice? To implement NFC technology today, the choices are either to attach a tag to the system, or to embed a full-blown NFC reader chip in it. But the former provides only a dead-end memory function, and does not support fully bi-directional data exchange or any means of energy harvesting. The latter is complex due to the front end design and imposes a heavy code load. It is also very expensive, both in terms of materials cost as well as development resources. So, desirable as it might be to add bi-directional NFC capability to devices, in cost-sensitive or commoditised products it has simply not been commercially viable before now. This article, however, describes how this has now changed. A new development from analog IC manufacturer ams has removed the technical and commercial impediments to implementing bidirectional NFC communication easily and at low cost and in a viable board footprint. As a result, electronics manufacturers can now enable any device with a host microcontroller to establish a twoway wireless connection between itself and any NFC-enabled mobile phone. The uses of NFC technology NFC is a set of standards defined by the NFC Forum, a consortium founded by Nokia, Philips and Sony which now has 150 members. NFC technology enables two devices to establish a connection via a 13.56MHz channel when in close proximity. NFC is widely used today to carry data for financial transactions, in end products such as contactless tickets. There are also some NFC-enabled mobile phones which can share contact lists or URLs with other mobile phones. NFC technology is also very widely adopted in Radio-Frequency Identification (RFID) systems, where it enables applications such as asset tracking and access control. How NFC is implemented today As a data link, an NFC channel can be designed to communicate in one of two ways. The first is passive communication, whereby the initiator device (the reader) provides the carrier field and the Page 2 / 7

3 target device (the tag) replies by modulating this field. The RFID reader reads information from the tags, which store information in an embedded memory. This type of communication is widely used for authentication or identification purposes. The second communication mode is active, fully bi-directional communication, in which two NFCenabled devices exchange data over a half-duplex link. This kind of communication channel can be used, for instance, for transferring a file, contact information, a URL or pictures between two NFCenabled mobile phones. It provides a more versatile data connection than passive NFC, facilitating a larger number of applications. But this active communication mode today requires the implementation of a complex NFC protocol stack in the devices on both sides of the link. And in terms of hardware, a full-blown NFC reader needs to be embedded in the system. But the implementation of a reader imposes considerable costs not only in the bill-of-materials (BOM), but also in terms of power, space and development effort: A reader requires a far more intricate antenna design than a tag does. This occupies valuable board space, and the complex matching network raises BOM costs. To design an NFC reader requires considerable RF and EMC expertise, and entails a long development process. The design cannot be self-powered (from harvested energy), because the reader s antenna draws around mA while transmitting the RF field. This means that the design must either draw power from the host system s battery, or use its own battery power supply. These drawbacks explain why, despite the appeal of enabling NFC connections with the huge installed base of smartphones, the technology has not to date been built into commodity or low-cost devices, gadgets or sensors. The low-cost alternative of adding an NFC tag to low-cost devices allows for only a restricted set of applications, limited to the reading of a unique ID and the static contents of the tag s memory. New NFC interface IC (NFiC) architecture To support low-cost but capable contactless links within the NFC framework, then, a solution is required which offers more functionality and flexibility in the communications channel than a simple ISO 14443A tag, but which avoids the high cost and complexity of NFC reader implementations. A new architecture from ams, called the NFC interface IC (NFiC, see Figure 1) promises to provide this middle way. Page 3 / 7

4 Fig. 1: the new NFiC architecture introduced by ams Its RF circuit design is similar to that of a passive tag, using a small and simple antenna. But the NFiC architecture breaks new ground because through this low-cost air interface it supports fully bidirectional NFC communication, controlled via an interface to any microcontroller, and completely powered by harvested energy. This offers the following advantages: The NFiC can be used for NFC-compatible bi-directional data exchange The RF circuit is easy to design The NFiC is not a parasite on the host system s power, since the energy it harvests powers both the NFiC chip itself and the MCU which controls it The fast MCU interface in the NFiC supports data rates up to 848kbps Since the NFiC behaves like a tag, its NFC protocol stack is only a small portion of the fullblown, complex NFC stack. This is easy to implement on a host MCU. Like a tag, an NFiC device can be certified much more easily than an NFC reader An implementation of the NFiC architecture available today, the AS3953 NFC Interface IC from ams, enables any device or gadget that has a host microcontroller to offer bi-directional NFC communications (see Figure 2). This IC provides an RF front-end offering integrated ISO 14443A data framing, an SPI interface to a host MCU, and an energy-harvesting and power management system. In addition, the internal EEPROM can be used to store data or to deliver a programmable passive wake-up pattern. Since it is fully compliant with the ISO 14443A standard and requires only a small NFC protocol stack, it can be integrated with less efforts compared to a NFC Reader IC. Page 4 / 7

5 Fig. 2: block diagram of the AS3953 NFC Interface IC from ams Page 5 / 7

6 Applications for NFiC The NFiC architecture provides the ideal way to make any device NFC-compliant, while offering a cheap bi-directional interface to an NFC phone. Market segments which can use this technology include: Interactive smart cards and smart cards with displays Electronic shelf labels used in the retail sector Medical devices Simple Secured Bluetooth or WiFi pairing via NFC Consumer electronics Passive device programming, personalisation and activation (such as regional settings configured on a production line) One interesting application to illustrate the potential is an NFC-compliant medical device. Today, device manufacturers are responding to demand from patients to be able to connect their medical device to their smartphone by adding a Bluetooth module to the medical device. Unfortunately, a Bluetooth module consumes a large amount of power an important drawback for battery-powered devices and is expensive, adding to the device s BOM. Implementing the NFiC architecture in the medical device eliminates these drawbacks. The BOM for a device such as the AS3953 would require only one external component, compared to the 16 components typically required for a reader IC front-end. The energy harvesting capability means it has no effect on battery runtime. In fact, implementing NFiC can have a surprisingly radical effect on system architecture. The main building blocks of a typical medical device are: Display Memory User interface (such as buttons, LEDs, buzzers) Processor Battery Power management system Sensor Page 6 / 7

7 With bi-directional NFC capability added, so that the device can talk to an NFC-enabled smartphone, the phone itself can provide the display, memory, user interface (in the form of an app) and complex processing functions. This means that the medical device can be made from just the NFiC device, a sensor, a simple MCU and a battery. The addition of a simple, low-cost NFiC chip thus makes the host device not only vastly cheaper, but also provides for a much more enjoyable and attractive user experience through being rendered as a smartphone app. In conclusion, then, an NFiC interface chip implemented in any device with an MCU provides a means to offer a more secure and versatile NFC link than a passive tag allows, while retaining a tag s advantages of low cost, low power consumption, small footprint, and ease of integration. For more information about ams AS3953 NFiC product, please go to For further information ams AG Tel: +43 (0) info@ams.com Page 7 / 7