Important

This repository has moved to https://codeberg.org/hohlerde/go-nxprd

go-nxprd

go-nxprd is a very simple wrapper written in GO for NXP's NFC Reader Library (NxpRdLib) in order to interface with the NXP EXPLORE-NFC expansion board for the Raspberry Pi.

Right now only Mifare Ultralight cards are supported for reading and writing bytes. This may change in the future, but currently I only have the Ultralight card that was shipped with the NFC board.

This wrapper was heavily inspired by svvitale's nxppy python wrapper. I use a slightly modified version of his nice bash script (get_nxpRdLib.sh).

License

All files in this repository are distributed under the MIT license.

External components

This wrapper is heavily based on NXP's example code (mainly MIFAREClassic and BasicDiscoveryLoop). The example code was reorganized and adjusted to be used from a GO wrapper. NXP still retains full copyright and ownership of the example code and the NFC Reader Library. The license conditions that need to be accepted in order to use this project in conjunction with the NFC Reader Library can be found in the document NXP_Library_License.pdf.

Compatibility

Tested with GO 1.6.3 on Raspian Jessie.

Requirements

The EXPLORE-NFC board relies on SPI being enabled. Please enable SPI using raspi-config prior to using go-nxprd. You may follow this tutorial from raspberrypi-spy.

As go-nxprd is a GO wrapper for NXP's C based NFC Reader Library, you need to install and configure GO on your Raspberry Pi. Instructions can be found at https://golang.org/doc/install.

Installation

go-nxprd uses cgo to interface the NFC Reader Library, so before using the wrapper please make sure you have a working gcc and cmake (used for building the NFC Reader Library) installed.

The easiest way is to use the script get_nxpRdLib.sh in the repository. It will download the Reader Library sources from DropBox, extract them to the folder nxp and run cmake to build the library for the EXPLORE-NFC board. Beforehand it will check whether the debian packages build-essential and cmake are installed and if not, will install them. Therefore, the script should be run with root privileges.

cgo relies on the original folder structure of the Reader Library in the nxp folder, so better don't change it. You'll find the compiled NFC Reader Library in the nxp/build/linux folder.

If the NFC Reader Library was build successfully, you can try to build the GO based test application for Mifare Ultralight cards. It is located under cmd/gomful in the repository. As the NFC Reader Library will be statically linked to the wrapper, you need to pass some extra parameters to GO's build command:

go build --ldflags '-extldflags -static' .

This will build the test application in the current folder. You'll find the build command in the script build.sh in the gomful folder. After a successfull build you can start the application simply by using:

./gomful

The output may be similar to the following:

Mifare Ultralight Test

Place a card near the reader and press <Enter>


Card            : MifareUL
Tag type        : 2
Technology type : A
UID             : 0x04 0x90 0x98 0xC2 0x37 0x30 0x81
ATQ(A)          : 0x44 0x00
SAK             : 0x00

Trying to read memory pages 0-15:

Page 00: 0x04 0x90 0x98 0x84
Page 01: 0xC2 0x37 0x30 0x81
Page 02: 0x44 0x48 0x00 0x00
Page 03: 0x00 0x00 0x00 0x00
Page 04: 0x00 0x00 0x00 0x00
Page 05: 0x00 0x00 0x00 0x00
Page 06: 0x00 0x00 0x00 0x00
Page 07: 0x00 0x00 0x00 0x00
Page 08: 0x00 0x00 0x00 0x00
Page 09: 0x00 0x00 0x00 0x00
Page 10: 0x00 0x00 0x00 0x00
Page 11: 0x00 0x00 0x00 0x00
Page 12: 0x00 0x00 0x00 0x00
Page 13: 0x00 0x00 0x00 0x00
Page 14: 0x00 0x00 0x00 0x00
Page 15: 0x00 0x00 0x00 0x00

Usage

To use go-nxprd in your GO application simply use the following import statement:

import "github.com/hohlerde/go-nxprd"

The main package of the wrapper is nxprd. In order to detect and read a card/tag the wrapper and also the NFC Reader Library need to be initialized. This is done by calling nxprd.Init():

err := nxprd.Init()
if err != nil {
    // handle error
}

Now you are ready to select a card/tag by calling Discover(). Please note that the Discover function blocks the caller. It has an optional timeout parameter, which can be used to specify how long the function should try to detect a card/tag before returning. The default timeout is 1000ms.

dev, err := nxprd.Discover(5000) // timeout = 5s
if err != nil {
    // handle error
}

If a card/tag could be detected, it can be accessed through the Device structure returned by Discover().

Parameters of the card/tag can be simply accessed by the Params member.

// Prints the UID of the card/tag
fmt.Printf("%+v", dev.Params.UID)

And if we have a Mifare Ultralight card, we can even read and write data.

// Right now only Mifare Ultralight cards are supported
if dev.Params.DevType == MifareUL {
    // Read all bytes (4) of page/block 10
    buffer, err := dev.Reader.ReadBlock(10)
    if err != nil {
        // handle error
    }

    buffer[0] = 66 // Change the first byte of page/block 10

    // and write it back to page 10.
    err = dev.Writer.WriteBlock(10, buffer)
    if err != nil {
        // handle error
    }
}

At the end we need to cleanup the wrapper and the NFC Reader Library by calling DeInit().

nxprd.DeInit()

As an example you also may want to take a look at the test application.

Feedback

Feedback and PRs are always welcome!