NXP Semiconductors NFC Tandem User manual

NFC Tandem User Manual
Rev. 0.2 — 17 August 2018 User manual
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Document information
Information Content
Keywords NFC, PN7150, NTAG-I2C plus
Abstract This user manual describes the design, the use and the software aspects of
the NFC Tandem board.

NXP Semiconductors NFC Tandem User Manual
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Revision history
Rev Date Description
0.2 20180817 Fix broken links
0.1 20171017 Initial version

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1 Introduction
The present document describes the NFC Tandem concept based on PN7150 NFC
Controller (see [1]) and NTAG I2C plus NFC connected tag (see [2]) sharing one unique
antenna.
The NFC Tandem concept offers combination of "no power" NFC functionality of NTAG
I2C plus and full NFC functionality of PN7150 when powered on. NTAG I2C plus being
visible over NFC interface until the PN7150 gets enabled, basically when device is
being powered-on. NTAG I2C plus remaining accessible from the host through the I2C
interface.
This document first gives an overview of the use cases offered by NFC Tandem.
Then it presents the NFC Tandem reference design, providing matching guidelines and
pointing to the related software ressources.
Finally it describes NFC Tandem demonstration setup.

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2 Use Cases
Combining PN7150 Full NFC controller solution and NTAG I2C plus zero-power
operation, NFC Tandem concept enables innovative use cases.
The following examples relates to Gateways and Set Top Boxes applications but are of
course not exhaustive and could also be applicable to some other applications.
Those use cases are shown using NFC Tandem demonstration setup (see Section 4).
2.1 Service configuration
As first step, NTAG I2C plus memory could be initiliazed with a link to the Operator
related phone application. This way, before powering-on the device (can even be done
prior to unboxing), tapping his NFC phone user will be guided to download the application
from the store. If already installed, the application will automatically be launched. The
application can instruct the user how to connect and install the device.
Then the phone application can allow activating Gateway or Set Top Box device by
transferring credentials to NTAG I2C plus memory via NFC. This could eventually been
done by in the shop by the merchant (device inbox). When powered-on, the host reading
those credentials from the NTAG I2C plus memory through I2C can perform device
activation over the network.
2.2 WiFi and IoT node pairing
When powered-on, the device can share WiFi credential of the network over NFC (thanks
to PN7150). When tapped, NFC phones retrieving this information will automatically
connect to the WiFi network without no other user action than simple confirmation. WiFi
credential can also be transfered in the same way to another device e.g. a WiFi repeater.
PN7150 is also capable of retrieving NFC information offering simplified pairing of IoT
nodes supporting NFC Smart commissioning: just tapping the node to the device allows
getting it added to the network in a simple and secured way. For more details about
Smart NFC commissioning refer to [4].
2.3 Error diagnostic and assistance
NTAG I2C plus memory can be used to store useful information during runtime for later
error diagnostic and assistance. These information being accessible from NFC interface
when device is powered off (or in case of network issue), it can be interpreted by phone
application to troubleshoot. Alternatively, it can be a source of analysis by manufacturer
in case of customer return.

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3 NFC Tandem reference design
3.1 Schematics
Figure 1. NFC Tandem reference design schematics - PN7150 and connectors
Figure 2. NFC Tandem reference design schematics - NtagI2C and antenna

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3.2 Matching guide
The NFC Tandem reference design comprised of 2 matching/tuning areas, respectively
for PN7150/NTAG I2C plus, influencing each other.
Figure 3. NFC Tandem matching/tuning
3.2.1 Step 1 - Reader matching
•Plug TX1 and TX2 to an NWA/NVA and enable the switching transistors (VBAT =
High/3V3/5V)
•Just match like a "normal" reader matching using NWA / VNA
•Define matching impedance to e.g. 30Ohms
•Bandwitdh resistors serial or paralell (shown) possible
–Parallel e.g. 10kOhms
–Serial e.g. 1,8 Ohms

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Figure 4. NFC Tandem reader matching
3.2.2 Step 2 - Ntag tuning
•Disable switching transistors (V_BAT = low/GND)
•Place 33pF for C11 & C12
–Outcome will be that resonance frequency will be lower than 13,56MHz
–Will be re-adjusted in the next step

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Figure 5. NFC Tandem Ntag tuning
3.2.3 Step 3 - Re-adjust reader matching
•Now the C9 & C10 values defined in Step 1 need to be re-adjusted
–Therefore enable reader mode / disable NTAG
•Reduce C9 & C10 by 2 x C11(=C12)
–e.g. C9 & C10 were 100pF à C11 = 33pF
–New C9 & C10 = 100pF - 2x33pF = 34pF
•C_fine can now be used to fine tune the reader matching to 13,56MHz

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Figure 6. NFC Tandem reader matching re-adjusting
3.2.4 Step 4 - Check Ntag tuning
•Enable NTAG mode (see Step 1)
•Check resonance frequency
–Use contactless method to check reflection on the antenna
–Should be around 14.0 – 14.5 MHz
3.3 Software
Even if sharing the same I2C bus, PN7150 and NTAG I2C plus are independent from
software perspective.
Refer to the respective software support for more information:
For PN7150 refer to [1], and for NTAG I2C plus see [2].

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4 NFC Tandem demonstration
NFC Tandem functionalities can be demonstrated using NFC Tandem reference
design board together with OM29110/RPI or OM29110/ARD Interface boards (see [3])
respectively allowing connection to Raspberry Pi board (see [5]) or Arduino compatible
boards (e.g. UDOO Neo see [6]).
Figure 7. NFC Tandem board
4.1 Hardware setup
In order to run NFC Tandem demonstration, the following hardware pieces are required:
¤ a microSD card of at least 4Gb (2Gb sufficient for Raspberry Pi setup)
¤ and a computer board, either:
•Raspberry Pi, any B model (see [5])
+ WLan USB Module (except for Raspberry Pi 3 version where WiFi module is
integrated): e.g. WiPi (see [14])
Figure 8. Raspberry Pi board and WiPi module
•or UDOO Neo Extended or Full version, since including WiFi module (see [6])