NFC

From postmarketOS

Near-field communication (NFC) can be used for contactless exchange of data over short distances. Different approaches exist on Linux to support it:

  • libnfc: userspace implementation, but mostly for desktop (e.g. USB) readers
  • Android NFC HAL: doesn't really work outside Android, probably mostly proprietary implementations
  • Linux NFC subsystem: NFC abstraction in the (mainline) Linux kernel with support for many different (also embedded) NFC chips

For smartphones/embedded devices the Linux NFC subsystem is the most suitable one, because it can be set up normally in the device tree like other hardware. Unfortunately, the NFC subsystem has been somewhat unmaintained for quite some time, and especially the userspace portion of it: Neard.

However, the main problem when testing NFC is a lack of applications that can make use of the Linux NFC subsystem. If you know any useful applications, please add them here. Also note that there is support for NFC/Neard in Qt if you want to build an application that makes use of NFC yourself.

Devices with NFC support

If your device runs the mainline kernel, and has a NFC chip that is supported in mainline's Linux NFC subsystem it should be fairly easy to add it to the device tree. Check the available NFC device tree bindings for details. Otherwise, these devices in postmarketOS already support NFC to some extent:

Device Codename Category Status
Xiaomi Redmi Note 10 Pro xiaomi-sweet Y
Google (ASUS) Nexus 7 (2012) asus-grouper community Y
Google (ASUS) Nexus 7 (2012) GSM asus-tilapia community Y
LG Optimus Vu lg-p895 community Y
Samsung Galaxy A3 (2015) samsung-a3 community Y
Samsung Galaxy A5 samsung-a5 community Y
Samsung Galaxy E7 samsung-e7 community Y
Xiaomi Mi Note 2 xiaomi-scorpio community Y
Google Pixel 3a google-sargo testing P
Huawei Ascend G7 huawei-g7 testing Y
Microsoft Lumia 640 microsoft-dempsey testing Y
Nokia Lumia 630 nokia-moneypenny testing Y
Nokia Lumia 730 nokia-superman testing Y
Nokia Lumia 830 nokia-tesla testing Y
OLIMEX Teres 1 teres_i testing Y
OnePlus 3T oneplus-oneplus3t testing Y
OnePlus 5 oneplus-cheeseburger testing Y
OnePlus 5T oneplus-dumpling testing Y
OnePlus 8 Pro oneplus-instantnoodlep testing Y
Qualcomm Snapdragon 410 qcom-msm8916 testing P
Samsung Galaxy A7 (2015) samsung-a7 testing Y
Samsung Galaxy Ace 2 GT-I8160 samsung-codina testing Y
Samsung Galaxy Ace 4 samsung-heatqlte testing Y
Samsung Galaxy Core Prime LTE samsung-rossa, samsung-cprime testing Y
Samsung Galaxy Grand Prime (SM-G530W) samsung-fortuna, samsung-gprimeltecan testing Y
Samsung Galaxy Grand Prime (SM-G530Y) samsung-fortunaltezt testing Y
Samsung Galaxy S Advance samsung-janice testing Y
Volla Phone 22 volla-mimameid testing P
Xiaomi Mi 11 Lite 4G xiaomi-courbet testing Y
Xiaomi Mi 5 xiaomi-gemini testing Y
Xiaomi Mi 5s Plus xiaomi-natrium testing Y
Xiaomi Mi 6 xiaomi-sagit testing Y
Xiaomi Mi 9T / Redmi K20 xiaomi-davinci testing Y
Xiaomi Mi Note 10 Lite xiaomi-toco testing Y
Xiaomi POCO X3 NFC xiaomi-surya testing Y

Testing

At the moment there are not many useful applications for testing NFC. As a basic test, you can use nfctool (from apk add neard) to poll for devices:

$ nfctool -d nfc0 -1 -p
nfc0:
          Tags: [ ]
          Devices: [ ]
          Protocols: [ Felica MIFARE Jewel ISO-DEP ISO-15693 ]
          Powered: Yes
          RF Mode: None
          lto: 0
          rw: 0
          miux: 0

Start polling on nfc0 as initiator

Targets found for nfc0
  Tags: [ tag0 ]
  Devices: [ ]

If you hold some other NFC-capable device close to the NFC antenna, it should find a NFC tag and show it. Many chip cards nowadays have NFC, or maybe you can use another smartphone.

Note Note: You may need to search for a while to find a working spot on the phone close to the NFC antenna. It could be anywhere on the back or anywhere on the front so just search for a bit before you give up.

Reading NFC tags

For advanced usage you should start the Neard daemon (rc-service neard start). Neard then provides a DBUS API similar to BlueZ for Bluetooth that allows reading/writing NFC tags for example.

The easiest way to test it is using the Neard test scripts, for example with test-adapter and test-tag. Unfortunately Neard hasn't been updated for a long time so they still use Python 2, but there is an open pull request which you can use with Python 3

Upstream is looking for potential maintainers and testers of the Linux NFC subsystem, so if you would like to help, consider posting on the linux-nfc mailing list.

See also