External NFC Service (native style) for Android

Library for interaction with ACS NFC readers over USB; external NFC support Android devices.

Features:

• External NFC reader management and interaction
• Parallell use of external and/or internal NFC (i.e. in the same activity, both enabled at the same time)
• Support for both tags and Android devices (Host Card Emulation), simultaneously
• Use of forked android.nfc classes (Ndef, MifareUltralight, IsoDep, etc) for Android 10+ support.

As this project very much simplifies implementation for use-cases requiring external NFC readers, it saves a lot of development time (2-8 weeks depending on use-case and previous knowledge).

Bugs, feature suggestions and help requests can be filed with the issue-tracker. DO NOT send me emails unless you're prepared to pay for my time.

License

Apache 2.0

Usage

This repository contains source code for

• A server library; services for interaction with the readers & tags
• A client library (i.e. API), receiving NFC-related intents
• An NFC library - Android adaptation of NFC Tools
• Demonstration apps
  • Basic server app for activation of the USB and/or bluetooth NFC background service. The rest of the examples interacts with the services exported by this app.
  • Basic client app.
  • NXP API client for MIFARE SDK. Deprecated for version 2.0.0 of the library; due to Android security for hidden classes in Android 9+.
  • Web Kiosk client with javascript bindings

There is also a Host Card Emulation client app for use with the Basic client app as well as Android-to-Android communication.

External NFC reader API

The API defines

• broadcast actions
  • service start / stop and status
  • reader open / close and status
  • tag connect / disconnect
• extras objects for interaction with readers
  • disable beeps
  • display text
  • configure NFC tech types (PICC)
  • enable/disable LEDs
  • run custom commands
  • and more..
• abstract activities for interaction with built-in and external NFC (simultaneously)
• these currently depend on the NDEF Tools for Android project.
• Programmatically start and stop the service (see methods startService() and stopService() in the NfcExternalDetectorActivity class in for an example).

Supported readers

Currently the ACS readers

• ACR 122U (API)
• ACR 1222L (API)
• ACR 1251U (API)
• ACR 1252U (API)
• ACR 1255U-J1 (API) - NOTE: bluetooth support in beta
• ACR 1281U-C1 (API)
• ACR 1283L (API)

are supported and must be connected to your Android device via an On-The-Go (OTG) USB cable.

Additional ACR readers might work depending on their command set, however custom reader commands will (like LED, beep etc) will not be available.

Supported tag technology

The following tags are supported by the service

• Mifare Ultralight familiy
  • Mifare Ultralight
  • NTAG 21x with FAST READ
• Mifare Classic and friends
  • Not recommended due to security and compatibility issues
• Desfire EV1 tags
• Host Card Emulation - interaction with Android devices.

The readers can for the most part can be enabled for all tag types at the same time, including Host Card Emulation.

Please note:

• Some readers only support a subset of the above tags
• For ACR 122U the Mifare Classic does not work well.
• No built-in NDEF support for Desfire EV1 cards

Configuration options

• assume all NTAG21x Mifare Ultralight targets. This improves read speed, particullary for the tags which have legacy equivalents, like NTAG 210 and 213
• read only tag UIDs, ignore other tag data. This improves read speed.
• read NDEF data automatically
• read UID for Desfire EV1 targets automatically

Reader connection

Note that not all Android devices actually have an USB hub, in which case no USB devices work.

Does the ACR reader not light up when connected to your device, even after the service asks for USB permissions? The ACR reader shuts down if there is not enough battery, so try charging your battery more, or connect external power.

If you are using external power, be aware that the connection order (device, reader, power) might be important. Known symptom:

• Seeing an USB permissions window that disappears rather quickly.

Tag detection

There is quite a few types of tags out there, and if your tag type is not recognized, please let me know. If the tag does not register at all, make sure that auto polling is configured, and that the right protocols are enabled. Use the below utility apps for tweaking your reader settings.

Reader setting utility apps

You might be interested in

• ACR 1222L USB NFC Reader Utils
• ACR 122 USB NFC Reader Utils
• ACR 1251 USB NFC Reader Utils
• ACR 1252 USB NFC Reader Utils
• ACR 1281 USB NFC Reader Utils

for configuration of your reader. Approximately the same configuration options are available using this API.

See also

This project contains adapted code from

• NFC Tools for Java
• SMARTRAC SDK for Android NFC NTAG

History

• 2.1.0: Improve bluetooth handling, various bug fixes and a few improvements.
• 2.0.0: Moved to wrapped android.nfc NFC android classes + various refactorings.
• 1.0.0: Library using native NFC android classes