Visual Basic .NET - NFC/RFID Bricklet

This is the description of the Visual Basic .NET API bindings for the NFC/RFID Bricklet. General information and technical specifications for the NFC/RFID Bricklet are summarized in its hardware description.

An installation guide for the Visual Basic .NET API bindings is part of their general description.

Examples

The example code below is Public Domain (CC0 1.0).

Scan For Tags

Download (ExampleScanForTags.vb)

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Imports System
Imports Tinkerforge

Module ExampleScanForTags
    Const HOST As String = "localhost"
    Const PORT As Integer = 4223
    Const UID As String = "XYZ" ' Change XYZ to the UID of your NFC/RFID Bricklet

    Private currentTagType As Byte = 0

    ' Callback subroutine for state changed callback
    Sub StateChangedCB(ByVal sender As BrickletNFCRFID, ByVal state As Byte, _
                       ByVal idle As Boolean)
        If state = BrickletNFCRFID.STATE_REQUEST_TAG_ID_READY Then
            Dim tagType As Byte
            Dim tidLength As Byte
            Dim tid() As Byte

            sender.GetTagID(tagType, tidLength, tid)

            If tidLength = 7 Then
                Console.WriteLine("Fount tag of type {0} with ID [{1:X} {2:X} {3:X} {4:X} {5:X} {6:X} {7:X}]",
                                  tagType, tid(0), tid(1), tid(2), tid(3), tid(4), tid(5), tid(6))
            Else
                Console.WriteLine("Fount tag of type {0} with ID [{1:X} {2:X} {3:X} {4:X}]",
                                  tagType, tid(0), tid(1), tid(2), tid(3))
            End If
        End If

        ' Cycle through all types
        If idle Then
            currentTagType = Convert.ToByte((currentTagType + 1) Mod 3)
            sender.requestTagID(currentTagType)
        End If
    End Sub

    Sub Main()
        Dim ipcon As New IPConnection() ' Create IP connection
        Dim nr As New BrickletNFCRFID(UID, ipcon) ' Create device object

        ipcon.Connect(HOST, PORT) ' Connect to brickd
        ' Don't use device before ipcon is connected

        ' Register state changed callback to subroutine StateChangedCB
        AddHandler nr.StateChangedCallback, AddressOf StateChangedCB

        ' Start scan loop
        nr.RequestTagID(BrickletNFCRFID.TAG_TYPE_MIFARE_CLASSIC)

        Console.WriteLine("Press key to exit")
        Console.ReadLine()
        ipcon.Disconnect()
    End Sub
End Module

Write Read Type 2

Download (ExampleWriteReadType2.vb)

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Imports System
Imports Tinkerforge

Module ExampleWriteReadType2
    Const HOST As String = "localhost"
    Const PORT As Integer = 4223
    Const UID As String = "XYZ" ' Change XYZ to the UID of your NFC/RFID Bricklet

    ' Callback subroutine for state changed callback
    Sub StateChangedCB(ByVal sender As BrickletNFCRFID, ByVal state As Byte, _
                       ByVal idle As Boolean)
        If state = BrickletNFCRFID.STATE_REQUEST_TAG_ID_READY Then
            System.Console.WriteLine("Tag found")

            ' Write 16 byte to pages 5-8
            Dim dataWrite() As Byte = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}
            sender.WritePage(5, dataWrite)
            System.Console.WriteLine("Writing data...")
        ElseIf state = BrickletNFCRFID.STATE_WRITE_PAGE_READY Then
            ' Request pages 5-8
            sender.RequestPage(5)
            System.Console.WriteLine("Requesting data...")
        ElseIf state = BrickletNFCRFID.STATE_REQUEST_PAGE_READY Then
            ' Get and print pages

            Dim data As Byte() = sender.GetPage()
            Dim str As String = "" & data(0).ToString()
            For i As Integer = 0 To data.Length-1
                str = str & " " & data(i).ToString()
            Next
            System.Console.WriteLine("Read data: [{0}]", str)
        ElseIf (state And (1 << 6)) = (1 << 6) Then
            ' All errors have bit 6 set
            System.Console.WriteLine("Error: {0}", state)
        End If
    End Sub

    Sub Main()
        Dim ipcon As New IPConnection() ' Create IP connection
        Dim nr As New BrickletNFCRFID(UID, ipcon) ' Create device object

        ipcon.Connect(HOST, PORT) ' Connect to brickd
        ' Don't use device before ipcon is connected

        ' Register state changed callback to subroutine StateChangedCB
        AddHandler nr.StateChangedCallback, AddressOf StateChangedCB

        ' Select NFC Forum Type 2 tag
        nr.RequestTagID(BrickletNFCRFID.TAG_TYPE_TYPE2)

        Console.WriteLine("Press key to exit")
        Console.ReadLine()
        ipcon.Disconnect()
    End Sub
End Module

API

Since Visual Basic .NET does not support multiple return values directly, we use the ByRef keyword to return multiple values from a function.

All functions and procedures listed below are thread-safe.

Basic Functions

Class BrickletNFCRFID(ByVal uid As String, ByVal ipcon As IPConnection)

Creates an object with the unique device ID uid:

Dim nfcRFID As New BrickletNFCRFID("YOUR_DEVICE_UID", ipcon)

This object can then be used after the IP Connection is connected (see examples above).

Sub BrickletNFCRFID.RequestTagID(ByVal tagType As Byte)
Parameters:
  • tagType – Type: Byte, Range: See constants

To read or write a tag that is in proximity of the NFC/RFID Bricklet you first have to call this function with the expected tag type as parameter. It is no problem if you don't know the tag type. You can cycle through the available tag types until the tag gives an answer to the request.

Currently the following tag types are supported:

  • Mifare Classic
  • NFC Forum Type 1
  • NFC Forum Type 2

After you call RequestTagID() the NFC/RFID Bricklet will try to read the tag ID from the tag. After this process is done the state will change. You can either register the StateChangedCallback callback or you can poll GetState() to find out about the state change.

If the state changes to RequestTagIDError it means that either there was no tag present or that the tag is of an incompatible type. If the state changes to RequestTagIDReady it means that a compatible tag was found and that the tag ID could be read out. You can now get the tag ID by calling GetTagID().

If two tags are in the proximity of the NFC/RFID Bricklet, this function will cycle through the tags. To select a specific tag you have to call RequestTagID() until the correct tag id is found.

In case of any Error state the selection is lost and you have to start again by calling RequestTagID().

The following constants are available for this function:

For tagType:

  • BrickletNFCRFID.TAG_TYPE_MIFARE_CLASSIC = 0
  • BrickletNFCRFID.TAG_TYPE_TYPE1 = 1
  • BrickletNFCRFID.TAG_TYPE_TYPE2 = 2
Sub BrickletNFCRFID.GetTagID(ByRef tagType As Byte, ByRef tidLength As Byte, ByRef tid() As Byte)
Output Parameters:
  • tagType – Type: Byte, Range: See constants
  • tidLength – Type: Byte, Range: [0 to 255]
  • tid – Type: Byte Array, Length: 7, Range: [0 to 255]

Returns the tag type, tag ID and the length of the tag ID (4 or 7 bytes are possible length). This function can only be called if the NFC/RFID is currently in one of the Ready states. The returned ID is the ID that was saved through the last call of RequestTagID().

To get the tag ID of a tag the approach is as follows:

  1. Call RequestTagID()
  2. Wait for state to change to RequestTagIDReady (see GetState() or StateChangedCallback callback)
  3. Call GetTagID()

The following constants are available for this function:

For tagType:

  • BrickletNFCRFID.TAG_TYPE_MIFARE_CLASSIC = 0
  • BrickletNFCRFID.TAG_TYPE_TYPE1 = 1
  • BrickletNFCRFID.TAG_TYPE_TYPE2 = 2
Sub BrickletNFCRFID.GetState(ByRef state As Byte, ByRef idle As Boolean)
Output Parameters:
  • state – Type: Byte, Range: See constants
  • idle – Type: Boolean

Returns the current state of the NFC/RFID Bricklet.

On startup the Bricklet will be in the Initialization state. The initialization will only take about 20ms. After that it changes to Idle.

The functions of this Bricklet can be called in the Idle state and all of the Ready and Error states.

Example: If you call RequestPage(), the state will change to RequestPage until the reading of the page is finished. Then it will change to either RequestPageReady if it worked or to RequestPageError if it didn't. If the request worked you can get the page by calling GetPage().

The same approach is used analogously for the other API functions.

The following constants are available for this function:

For state:

  • BrickletNFCRFID.STATE_INITIALIZATION = 0
  • BrickletNFCRFID.STATE_IDLE = 128
  • BrickletNFCRFID.STATE_ERROR = 192
  • BrickletNFCRFID.STATE_REQUEST_TAG_ID = 2
  • BrickletNFCRFID.STATE_REQUEST_TAG_ID_READY = 130
  • BrickletNFCRFID.STATE_REQUEST_TAG_ID_ERROR = 194
  • BrickletNFCRFID.STATE_AUTHENTICATING_MIFARE_CLASSIC_PAGE = 3
  • BrickletNFCRFID.STATE_AUTHENTICATING_MIFARE_CLASSIC_PAGE_READY = 131
  • BrickletNFCRFID.STATE_AUTHENTICATING_MIFARE_CLASSIC_PAGE_ERROR = 195
  • BrickletNFCRFID.STATE_WRITE_PAGE = 4
  • BrickletNFCRFID.STATE_WRITE_PAGE_READY = 132
  • BrickletNFCRFID.STATE_WRITE_PAGE_ERROR = 196
  • BrickletNFCRFID.STATE_REQUEST_PAGE = 5
  • BrickletNFCRFID.STATE_REQUEST_PAGE_READY = 133
  • BrickletNFCRFID.STATE_REQUEST_PAGE_ERROR = 197
Sub BrickletNFCRFID.AuthenticateMifareClassicPage(ByVal page As Integer, ByVal keyNumber As Byte, ByVal key() As Byte)
Parameters:
  • page – Type: Integer, Range: [0 to 216 - 1]
  • keyNumber – Type: Byte, Range: See constants
  • key – Type: Byte Array, Length: 6, Range: [0 to 255]

Mifare Classic tags use authentication. If you want to read from or write to a Mifare Classic page you have to authenticate it beforehand. Each page can be authenticated with two keys: A (key_number = 0) and B (key_number = 1). A new Mifare Classic tag that has not yet been written to can be accessed with key A and the default key [0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF].

The approach to read or write a Mifare Classic page is as follows:

  1. Call RequestTagID()
  2. Wait for state to change to RequestTagIDReady (see GetState() or StateChangedCallback callback)
  3. If looking for a specific tag then call GetTagID() and check if the expected tag was found, if it was not found go back to step 1
  4. Call AuthenticateMifareClassicPage() with page and key for the page
  5. Wait for state to change to AuthenticatingMifareClassicPageReady (see GetState() or StateChangedCallback callback)
  6. Call RequestPage() or WritePage() to read/write page

The following constants are available for this function:

For keyNumber:

  • BrickletNFCRFID.KEY_A = 0
  • BrickletNFCRFID.KEY_B = 1
Sub BrickletNFCRFID.WritePage(ByVal page As Integer, ByVal data() As Byte)
Parameters:
  • page – Type: Integer, Range: [0 to 216 - 1]
  • data – Type: Byte Array, Length: 16, Range: [0 to 255]

Writes 16 bytes starting from the given page. How many pages are written depends on the tag type. The page sizes are as follows:

  • Mifare Classic page size: 16 byte (one page is written)
  • NFC Forum Type 1 page size: 8 byte (two pages are written)
  • NFC Forum Type 2 page size: 4 byte (four pages are written)

The general approach for writing to a tag is as follows:

  1. Call RequestTagID()
  2. Wait for state to change to RequestTagIDReady (see GetState() or StateChangedCallback callback)
  3. If looking for a specific tag then call GetTagID() and check if the expected tag was found, if it was not found got back to step 1
  4. Call WritePage() with page number and data
  5. Wait for state to change to WritePageReady (see GetState() or StateChangedCallback callback)

If you use a Mifare Classic tag you have to authenticate a page before you can write to it. See AuthenticateMifareClassicPage().

Sub BrickletNFCRFID.RequestPage(ByVal page As Integer)
Parameters:
  • page – Type: Integer, Range: [0 to 216 - 1]

Reads 16 bytes starting from the given page and stores them into a buffer. The buffer can then be read out with GetPage(). How many pages are read depends on the tag type. The page sizes are as follows:

  • Mifare Classic page size: 16 byte (one page is read)
  • NFC Forum Type 1 page size: 8 byte (two pages are read)
  • NFC Forum Type 2 page size: 4 byte (four pages are read)

The general approach for reading a tag is as follows:

  1. Call RequestTagID()
  2. Wait for state to change to RequestTagIDReady (see GetState() or StateChangedCallback callback)
  3. If looking for a specific tag then call GetTagID() and check if the expected tag was found, if it was not found got back to step 1
  4. Call RequestPage() with page number
  5. Wait for state to change to RequestPageReady (see GetState() or StateChangedCallback callback)
  6. Call GetPage() to retrieve the page from the buffer

If you use a Mifare Classic tag you have to authenticate a page before you can read it. See AuthenticateMifareClassicPage().

Function BrickletNFCRFID.GetPage() As Byte()
Returns:
  • data – Type: Byte Array, Length: 16, Range: [0 to 255]

Returns 16 bytes of data from an internal buffer. To fill the buffer with specific pages you have to call RequestPage() beforehand.

Advanced Functions

Function BrickletNFCRFID.GetAPIVersion() As Byte()
Returns:
  • apiVersion – Type: Byte Array, Length: 3, Range: [0 to 255]

Returns the version of the API definition (major, minor, revision) implemented by this API bindings. This is neither the release version of this API bindings nor does it tell you anything about the represented Brick or Bricklet.

Function BrickletNFCRFID.GetResponseExpected(ByVal functionId As Byte) As Boolean
Parameters:
  • functionId – Type: Byte, Range: See constants
Returns:
  • responseExpected – Type: Boolean

Returns the response expected flag for the function specified by the function ID parameter. It is true if the function is expected to send a response, false otherwise.

For getter functions this is enabled by default and cannot be disabled, because those functions will always send a response. For callback configuration functions it is enabled by default too, but can be disabled by SetResponseExpected(). For setter functions it is disabled by default and can be enabled.

Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

For functionId:

  • BrickletNFCRFID.FUNCTION_REQUEST_TAG_ID = 1
  • BrickletNFCRFID.FUNCTION_AUTHENTICATE_MIFARE_CLASSIC_PAGE = 4
  • BrickletNFCRFID.FUNCTION_WRITE_PAGE = 5
  • BrickletNFCRFID.FUNCTION_REQUEST_PAGE = 6
Sub BrickletNFCRFID.SetResponseExpected(ByVal functionId As Byte, ByVal responseExpected As Boolean)
Parameters:
  • functionId – Type: Byte, Range: See constants
  • responseExpected – Type: Boolean

Changes the response expected flag of the function specified by the function ID parameter. This flag can only be changed for setter (default value: false) and callback configuration functions (default value: true). For getter functions it is always enabled.

Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

For functionId:

  • BrickletNFCRFID.FUNCTION_REQUEST_TAG_ID = 1
  • BrickletNFCRFID.FUNCTION_AUTHENTICATE_MIFARE_CLASSIC_PAGE = 4
  • BrickletNFCRFID.FUNCTION_WRITE_PAGE = 5
  • BrickletNFCRFID.FUNCTION_REQUEST_PAGE = 6
Sub BrickletNFCRFID.SetResponseExpectedAll(ByVal responseExpected As Boolean)
Parameters:
  • responseExpected – Type: Boolean

Changes the response expected flag for all setter and callback configuration functions of this device at once.

Sub BrickletNFCRFID.GetIdentity(ByRef uid As String, ByRef connectedUid As String, ByRef position As Char, ByRef hardwareVersion() As Byte, ByRef firmwareVersion() As Byte, ByRef deviceIdentifier As Integer)
Output Parameters:
  • uid – Type: String, Length: up to 8
  • connectedUid – Type: String, Length: up to 8
  • position – Type: Char
  • hardwareVersion – Type: Byte Array, Length: 3, Range: [0 to 255]
  • firmwareVersion – Type: Byte Array, Length: 3, Range: [0 to 255]
  • deviceIdentifier – Type: Integer, Range: [0 to 216 - 1]

Returns the UID, the UID where the Bricklet is connected to, the position, the hardware and firmware version as well as the device identifier.

The position can be 'a', 'b', 'c' or 'd'.

The device identifier numbers can be found here. There is also a constant for the device identifier of this Bricklet.

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done by assigning a procedure to an callback property of the device object:

Sub MyCallback(ByVal sender As BrickletNFCRFID, ByVal value As Short)
    Console.WriteLine("Value: {0}", value)
End Sub

AddHandler nfcRFID.ExampleCallback, AddressOf MyCallback

The available callback property and their type of parameters are described below.

Note

Using callbacks for recurring events is always preferred compared to using getters. It will use less USB bandwidth and the latency will be a lot better, since there is no round trip time.

Event BrickletNFCRFID.StateChangedCallback(ByVal sender As BrickletNFCRFID, ByVal state As Byte, ByVal idle As Boolean)
Callback Parameters:
  • sender – Type: BrickletNFCRFID
  • state – Type: Byte, Range: See constants
  • idle – Type: Boolean

This callback is called if the state of the NFC/RFID Bricklet changes. See GetState() for more information about the possible states.

The following constants are available for this function:

For state:

  • BrickletNFCRFID.STATE_INITIALIZATION = 0
  • BrickletNFCRFID.STATE_IDLE = 128
  • BrickletNFCRFID.STATE_ERROR = 192
  • BrickletNFCRFID.STATE_REQUEST_TAG_ID = 2
  • BrickletNFCRFID.STATE_REQUEST_TAG_ID_READY = 130
  • BrickletNFCRFID.STATE_REQUEST_TAG_ID_ERROR = 194
  • BrickletNFCRFID.STATE_AUTHENTICATING_MIFARE_CLASSIC_PAGE = 3
  • BrickletNFCRFID.STATE_AUTHENTICATING_MIFARE_CLASSIC_PAGE_READY = 131
  • BrickletNFCRFID.STATE_AUTHENTICATING_MIFARE_CLASSIC_PAGE_ERROR = 195
  • BrickletNFCRFID.STATE_WRITE_PAGE = 4
  • BrickletNFCRFID.STATE_WRITE_PAGE_READY = 132
  • BrickletNFCRFID.STATE_WRITE_PAGE_ERROR = 196
  • BrickletNFCRFID.STATE_REQUEST_PAGE = 5
  • BrickletNFCRFID.STATE_REQUEST_PAGE_READY = 133
  • BrickletNFCRFID.STATE_REQUEST_PAGE_ERROR = 197

Constants

Const BrickletNFCRFID.DEVICE_IDENTIFIER

This constant is used to identify a NFC/RFID Bricklet.

The GetIdentity() function and the IPConnection.EnumerateCallback callback of the IP Connection have a deviceIdentifier parameter to specify the Brick's or Bricklet's type.

Const BrickletNFCRFID.DEVICE_DISPLAY_NAME

This constant represents the human readable name of a NFC/RFID Bricklet.