Go - NFC/RFID Bricklet

This is the description of the Go 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 Go API bindings is part of their general description. Additional documentation can be found on godoc.org.

Examples

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

Scan For Tags

Download (example_scan_for_tags.go)

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package main

import (
    "fmt"
    "github.com/Tinkerforge/go-api-bindings/ipconnection"
    "github.com/Tinkerforge/go-api-bindings/nfc_rfid_bricklet"
)

const ADDR string = "localhost:4223"
const UID string = "XYZ" // Change XYZ to the UID of your NFC/RFID Bricklet.

func main() {
    ipcon := ipconnection.New()
    defer ipcon.Close()
    nr, _ := nfc_rfid_bricklet.New(UID, &ipcon) // Create device object.

    ipcon.Connect(ADDR) // Connect to brickd.
    defer ipcon.Disconnect()
    // Don't use device before ipcon is connected.

    currentTagType := nfc_rfid_bricklet.TagTypeMifareClassic

    nr.RegisterStateChangedCallback(func(state nfc_rfid_bricklet.State, idle bool) {
        if idle {
            currentTagType = (currentTagType + 1) % 3
            nr.RequestTagID(currentTagType)
        }
        if state == nfc_rfid_bricklet.StateRequestTagIDReady {
            tagType, IDLength, tagID, _ := nr.GetTagID()
            fmt.Printf("Found tag of type %d with ID %v\n", tagType, tagID[:IDLength])
        }
    })

    // Start scan loop
    nr.RequestTagID(nfc_rfid_bricklet.TagTypeMifareClassic)

    fmt.Print("Press enter to exit.")
    fmt.Scanln()
}

Write Read Type2

Download (example_write_read_type2.go)

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package main

import (
    "fmt"
    "github.com/Tinkerforge/go-api-bindings/ipconnection"
    "github.com/Tinkerforge/go-api-bindings/nfc_rfid_bricklet"
)

const ADDR string = "localhost:4223"
const UID string = "XYZ" // Change XYZ to the UID of your NFC/RFID Bricklet.

func main() {
    ipcon := ipconnection.New()
    defer ipcon.Close()
    nr, _ := nfc_rfid_bricklet.New(UID, &ipcon) // Create device object.

    ipcon.Connect(ADDR) // Connect to brickd.
    defer ipcon.Disconnect()
    // Don't use device before ipcon is connected.

    nr.RegisterStateChangedCallback(func(state nfc_rfid_bricklet.State, idle bool) {
        if state == nfc_rfid_bricklet.StateRequestTagIDReady {
            fmt.Println("Tag found")

            dataWrite := [16]uint8{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}
            nr.WritePage(5, dataWrite)
            fmt.Println("Writing data...")
        } else if state == nfc_rfid_bricklet.StateWritePageReady {
            nr.RequestPage(5)
            fmt.Println("Requesting data...")
        } else if state == nfc_rfid_bricklet.StateRequestPageReady {
            data, _ := nr.GetPage()
            fmt.Printf("Read data: %v\n", data)
        } else if state&(1<<6) == (1 << 6) {
            fmt.Printf("Error: %v\n", state)
        }
    })

    // Select NFC Forum Type 2 tag
    nr.RequestTagID(nfc_rfid_bricklet.TagTypeType2)

    fmt.Print("Press enter to exit.")
    fmt.Scanln()
}

API

The NFC/RFID Bricklet API is defined in the package github.com/Tinkerforge/go-api-bindings/nfc_rfid_bricklet

Nearly every function of the Go bindings can return an DeviceError, implementing the error interface. The error can have one of the following values:

  • DeviceErrorSuccess = 0
  • DeviceErrorInvalidParameter = 1
  • DeviceErrorFunctionNotSupported = 2
  • DeviceErrorUnknownError = 3

which correspond to the values returned from Bricks and Bricklets.

All functions listed below are thread-safe.

Basic Functions

func nfc_rfid_bricklet.New(uid string, ipcon *IPConnection) (device NFCRFIDBricklet, err error)

Creates a new NFCRFIDBricklet object with the unique device ID uid and adds it to the IPConnection ipcon:

device, err := nfc_rfid_bricklet.New("YOUR_DEVICE_UID", &ipcon)

This device object can be used after the IPConnection has been connected (see examples above).

func (*NFCRFIDBricklet) RequestTagID(tagType TagType) (err error)

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 RegisterStateChangedCallback 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:

  • nfc_rfid_bricklet.TagTypeMifareClassic = 0
  • nfc_rfid_bricklet.TagTypeType1 = 1
  • nfc_rfid_bricklet.TagTypeType2 = 2
func (*NFCRFIDBricklet) GetTagID() (tagType TagType, tidLength uint8, tid [7]uint8, err error)

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 RegisterStateChangedCallback callback)
  3. Call GetTagID()

The following constants are available for this function:

  • nfc_rfid_bricklet.TagTypeMifareClassic = 0
  • nfc_rfid_bricklet.TagTypeType1 = 1
  • nfc_rfid_bricklet.TagTypeType2 = 2
func (*NFCRFIDBricklet) GetState() (state State, idle bool, err error)

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:

  • nfc_rfid_bricklet.StateInitialization = 0
  • nfc_rfid_bricklet.StateIdle = 128
  • nfc_rfid_bricklet.StateError = 192
  • nfc_rfid_bricklet.StateRequestTagID = 2
  • nfc_rfid_bricklet.StateRequestTagIDReady = 130
  • nfc_rfid_bricklet.StateRequestTagIDError = 194
  • nfc_rfid_bricklet.StateAuthenticatingMifareClassicPage = 3
  • nfc_rfid_bricklet.StateAuthenticatingMifareClassicPageReady = 131
  • nfc_rfid_bricklet.StateAuthenticatingMifareClassicPageError = 195
  • nfc_rfid_bricklet.StateWritePage = 4
  • nfc_rfid_bricklet.StateWritePageReady = 132
  • nfc_rfid_bricklet.StateWritePageError = 196
  • nfc_rfid_bricklet.StateRequestPage = 5
  • nfc_rfid_bricklet.StateRequestPageReady = 133
  • nfc_rfid_bricklet.StateRequestPageError = 197
func (*NFCRFIDBricklet) AuthenticateMifareClassicPage(page uint16, keyNumber Key, key [6]uint8) (err error)

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 RegisterStateChangedCallback 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 RegisterStateChangedCallback callback)
  6. Call RequestPage() or WritePage() to read/write page

The following constants are available for this function:

  • nfc_rfid_bricklet.KeyA = 0
  • nfc_rfid_bricklet.KeyB = 1
func (*NFCRFIDBricklet) WritePage(page uint16, data [16]uint8) (err error)

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 RegisterStateChangedCallback 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 RegisterStateChangedCallback callback)

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

func (*NFCRFIDBricklet) RequestPage(page uint16) (err error)

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 RegisterStateChangedCallback 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 RegisterStateChangedCallback 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().

func (*NFCRFIDBricklet) GetPage() (data [16]uint8, err error)

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

Advanced Functions

func (*NFCRFIDBricklet) GetAPIVersion() (apiVersion [3]uint8, err error)

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.

func (*NFCRFIDBricklet) GetResponseExpected(functionId Function) (responseExpected bool, err error)

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:

  • nfc_rfid_bricklet.FunctionRequestTagID = 1
  • nfc_rfid_bricklet.FunctionAuthenticateMifareClassicPage = 4
  • nfc_rfid_bricklet.FunctionWritePage = 5
  • nfc_rfid_bricklet.FunctionRequestPage = 6
func (*NFCRFIDBricklet) SetResponseExpected(functionId Function, responseExpected bool) (err error)

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:

  • nfc_rfid_bricklet.FunctionRequestTagID = 1
  • nfc_rfid_bricklet.FunctionAuthenticateMifareClassicPage = 4
  • nfc_rfid_bricklet.FunctionWritePage = 5
  • nfc_rfid_bricklet.FunctionRequestPage = 6
func (*NFCRFIDBricklet) SetResponseExpectedAll(responseExpected bool) (err error)

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

func (*NFCRFIDBricklet) GetIdentity() (uid string, connectedUid string, position rune, hardwareVersion [3]uint8, firmwareVersion [3]uint8, deviceIdentifier uint16, err error)

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 with the corresponding Register*Callback function, which returns a unique callback ID. This ID can be used to deregister the callback later.

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.

func (*NFCRFIDBricklet) RegisterStateChangedCallback(func(state State, idle bool)) (registrationId uint64)

A callback can be registered for this event with the RegisterStateChangedCallback() function. This function returns the ID of the registered callback. An added callback can be removed with the DeregisterStateChangedCallback(registrationId uint64) function.

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:

  • nfc_rfid_bricklet.StateInitialization = 0
  • nfc_rfid_bricklet.StateIdle = 128
  • nfc_rfid_bricklet.StateError = 192
  • nfc_rfid_bricklet.StateRequestTagID = 2
  • nfc_rfid_bricklet.StateRequestTagIDReady = 130
  • nfc_rfid_bricklet.StateRequestTagIDError = 194
  • nfc_rfid_bricklet.StateAuthenticatingMifareClassicPage = 3
  • nfc_rfid_bricklet.StateAuthenticatingMifareClassicPageReady = 131
  • nfc_rfid_bricklet.StateAuthenticatingMifareClassicPageError = 195
  • nfc_rfid_bricklet.StateWritePage = 4
  • nfc_rfid_bricklet.StateWritePageReady = 132
  • nfc_rfid_bricklet.StateWritePageError = 196
  • nfc_rfid_bricklet.StateRequestPage = 5
  • nfc_rfid_bricklet.StateRequestPageReady = 133
  • nfc_rfid_bricklet.StateRequestPageError = 197

Constants

nfc_rfid_bricklet.DeviceIdentifier

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

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

nfc_rfid_bricklet.DeviceDisplayName

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