ST released its newest NFC Forum Certification Release (CR) 13 device for automotive, the ST25R3920B. It brings improved active waveshaping to reduce under and overshoots, thus providing greater future-proofing for companies looking to build systems with long life spans. CR13 was highly symbolic as it brought support for CCC (Car Connectivity Consortium) Digital Key Reader for car doors and Digital Key CE (Card Emulation) on smartphones. In a nutshell, CR13 ensures that carmakers offer interoperable key systems using NFC. CR13.1 continues that trend by optimizing performance, thus making the digital car keys even more compelling. It was also an opportunity for ST to make the technology more accessible.
Table of Contents
- What’s wrong with contactless car keys today?
- Solving the interoperability issue to reach mass adoption
- NFC Forum CR13: thinking about NFC door locks, center consoles, and more
- What’s surprising about designing NFC modules with ST is the unsurprising path to design
What’s wrong with contactless car keys today?
Consumers are at the mercy of proprietary systems. One car model could work with one generation of phones, but a newer automotive could have different requirements. As a result, the lack of industry cooperation can leave customers frustrated and unwilling to adopt this new technology. NFC Forum CR13, and subsequent version, aim to make contactless car keys more practical. For instance, it ensures smartphones can still deliver a key even when in reduced power mode. When the smartphone is off and an icon asks the user to charge it, phone makers must maintain a minimum charge for NFC operation. Hence, customers no longer need to worry about battery life when using a phone as a car key.
Solving the interoperability issue to reach mass adoption
The industry solution to democratize digital car keys
Phones compliant with NFC Forum CR13 will be ready for CCC requirements. Most smartphones compatible with CR12 and EMVCo payment requirements should also pass CR13 certifications. Hence, the new Certification Release builds on existing standards to offer greater interoperability. Similarly, ST’s ST25R3920B provides one of the most advanced waveshaping capabilities, now essential for NFC Forum CR13 readers. Indeed, strict waveshape monotonicity tests are already in place in the EMVCo 3.0 standard when using NFC Card for payment, and the NFC Forum’s latest efforts aim to harmonize testing protocols among various standards.
The importance of waveshaping
Waveshaping is a method that adjusts the signal to match PICC (Proximity Integrated Circuit Cards) references. Its objective is to avoid overshoots and communication errors. Put simply, it fine-tunes coupling operations between the reader and the card without requiring rematching. For automotive makers, waveshaping is essential to meet the more rigorous standards put forth by the latest certification releases. For consumers, the standard means that more phones and door locks will become interoperable, improving the user experience.
The problem is that customizing the signal for specific applications can take time, and over the years, ST has had a lot of requests for help from customers. We even published technical documentation to guide users. One of the challenges before active waveshaping was to tune the antenna. Later, our first generation of active waveshaping devices allowed teams to tweak the signal in addition to the matching done on the PCB. It did help quite a bit, but we wanted to make the process even more accessible. We, therefore, worked to bring more straightforward solutions to help solve this issue with the ST25R3920B.
Optimizations to the active waveshaping
The ST25R3920B provides many more choices to fine-tune the signal. ST developed a graphical user interface to help teams visually select registers to shape the signal and manage the undershoot and overshoot patterns. Hence, while the device is connected to an oscilloscope, the GUI displays a representation of the signal where the engineer can pick every single wave and provide step-by-step adjustments while monitoring the outcome. With this immediate feedback and the granularity, fine-tuning the signal only takes minutes. The ST tool thus lowers the barrier to entry to help engineers get started and reduce friction in the early prototyping stages. The software is available upon request.
The ST25R3920B also distinguishes with features like the heartbeat function, which can help a reader identify whether it is interacting with a card or a smartphone. This is particularly useful in center console applications in automotive. Increasingly, cars use center consoles to charge phones wirelessly. The problem is that the Qi charger can potentially destroy regular NFC cards if it mistakes it for a phone and try to send a charge. Thanks to the heartbeat technology patented by ST, the reader can rapidly distinguish between the two by more precisely analyzing behaviors after communication ends.
Adoption of NFC Forum CR13
Traditionally, the industry takes about three years for a certification release to reach mass adoption. However, the NFC Forum is extending the grace period for makers to adopt CR13. Indeed, companies will have 72 months, instead of 18, to move from CR12 to the new versions. The NFC Forum thus takes into account the much longer development cycles in the automotive industry.
Yet, we can expect the transition to be quicker than usual. Indeed, most smartphones released in the last few years were compatible with NFC Forum CR13. Manufacturers will only need to release a software update to bring their operating system up to par. Similarly, the hardware and software to create compliant readers are already available. For instance, ST offers an RF abstraction layer for the ST25R3920B, the STSW-ST25RFAL002￼, which facilitates the creation of readers compatible with CR13.
NFC Forum CR13: thinking about NFC door locks, center consoles, and more
What’s special about NFC car key readers is that they don’t have to be special
NFC modules in cars are in three primary locations: the door handle, the B-pillar between the front and backside windows, and the center console inside the vehicle. The first two control the access to the vehicle by unlocking the doors and allowing for very different designs. The space within the door handle is tiny, thus requiring slim components and antennas. On the other hand, the B-pillar enables coils four times larger. All three locations play a different role. For instance, the module in the center console can authenticate a smartphone to adjust seat positions automatically. We could also imagine parental controls limiting maximum speeds when pairing the car with a teenager’s phone.
The trap for decision-makers and designers is to think that the three locations require entirely different systems. The strength of a reader IC like the ST25R3920B is that it can fit into all three areas. For instance, its vast operating temperature range of -40 ºC to +105 ºC means it works indoors and outdoors. The ST25R3920B easily fits anywhere in the vehicle, from the door handle to the center console. And having only one IC means only qualifying one component, thus greatly simplifying designs and operations.
What’s surprising about designing NFC modules with ST is the unsurprising path to design
Anyone interested in the ST25R3920B can grab an inexpensive¸ X-NUCLEO-NFC08A1 expansion board. The platform uses the ST25R3916B, which is identical but didn’t go through automotive certifications. We even offer a MISRA-C-compliant firmware stack, the STSW-ST25R002. Moreover, we provide an antenna-matching graphical user interface, the STSW-ST25R004, and a separate antenna-matching tool in eDesign Suite, to further facilitate developments.
A robust hardware and software ecosystem is fundamental because it reduces the time to market. For example, by merely using the X-NUCLEO board, developers can use the automatic antenna tuning and the ultra-low-power wake-up sequence. Engineers can then decide to add the same components in their final design, porting the code they used on the development boards. Hence, we’re not merely offering a product but a path to an application.
A couple of years ago, engineers needed to convince decision-makers to use NFC in vehicles. Then Mercedes adopted our ST25R reader in their E-Class models. Now, managers want a reader because keyless entry and smartphone pairing are all the rage. Hence, a successful design is future-proof and can anticipate the industry’s direction. An ST25R3920B NFC reader and an STM8 MCU can already create NFC Forum CR13.1 readers. Hence, investing in those components will yield returns for many years.