Shell - NFC/RFID Bricklet

This is the description of the Shell 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 Shell API bindings is part of their general description.

Examples

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

Scan For Tags

Download (example-scan-for-tags.sh)

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#!/bin/sh
# Connects to localhost:4223 by default, use --host and --port to change this

uid=XYZ # Change XYZ to the UID of your NFC/RFID Bricklet
tmp=$(mktemp)

# Create temporary file to keep track of current tag type
echo "0" > $tmp

# Handle incoming state changed callbacks
tinkerforge dispatch nfc-rfid-bricklet $uid state-changed\
 --execute "if [ {state} == request-tag-id-ready ]
              then tinkerforge call nfc-rfid-bricklet $uid get-tag-id
            fi;
            if [ {idle} ]
            then 
              tt=\$(cat $tmp)
              if [ \$tt -eq 0 ] 
                then tt=1
              elif [ \$tt -eq 1 ] 
                then tt=2
              elif [ \$tt -eq 2 ] 
                then tt=0
              fi
              echo \"\$tt\" > $tmp
              tinkerforge call nfc-rfid-bricklet $uid request-tag-id \$tt
            fi" &

# Start scan loop
tinkerforge call nfc-rfid-bricklet $uid request-tag-id tag-type-mifare-classic

echo "Press key to exit"; read dummy

kill -- -$$ # Stop callback dispatch in background

API

Possible exit codes for all tinkerforge commands are:

  • 1: interrupted (ctrl+c)
  • 2: syntax error
  • 21: Python 2.5 or newer is required
  • 22: Python argparse module is missing
  • 23: socket error
  • 24: other exception
  • 25: invalid placeholder in format string
  • 26: authentication error
  • 201: timeout occurred
  • 209: invalid argument value
  • 210: function is not supported
  • 211: unknown error

Command Structure

The common options of the call and dispatch commands are documented here. The specific command structure is shown below.

tinkerforge call nfc-rfid-bricklet [<option>..] <uid> <function> [<argument>..]
Parameters:
  • <uid> -- string
  • <function> -- string

The call command is used to call a function of the NFC/RFID Bricklet. It can take several options:

  • --help shows help for the specific call command and exits
  • --list-functions shows a list of known functions of the NFC/RFID Bricklet and exits
tinkerforge dispatch nfc-rfid-bricklet [<option>..] <uid> <callback>
Parameters:
  • <uid> -- string
  • <callback> -- string

The dispatch command is used to dispatch a callback of the NFC/RFID Bricklet. It can take several options:

  • --help shows help for the specific dispatch command and exits
  • --list-callbacks shows a list of known callbacks of the NFC/RFID Bricklet and exits
tinkerforge call nfc-rfid-bricklet <uid> <function> [<option>..] [<argument>..]
Parameters:
  • <uid> -- string
  • <function> -- string

The <function> to be called can take different options depending of its kind. All functions can take the following options:

  • --help shows help for the specific function and exits

Getter functions can take the following options:

  • --execute <command> shell command line to execute for each incoming response (see section about output formatting for details)

Setter functions can take the following options:

  • --expect-response requests response and waits for it

The --expect-response option for setter functions allows to detect timeouts and other error conditions calls of setters as well. The device will then send a response for this purpose. If this option is not given for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

tinkerforge dispatch nfc-rfid-bricklet <uid> <callback> [<option>..]
Parameters:
  • <uid> -- string
  • <callback> -- string

The <callback> to be dispatched can take several options:

  • --help shows help for the specific callback and exits
  • --execute <command> shell command line to execute for each incoming response (see section about output formatting for details)

Basic Functions

tinkerforge call nfc-rfid-bricklet <uid> request-tag-id <tag-type>
Parameters:
  • <tag-type> -- int (has symbols)
Output:

no output

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 request-tag-id 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 state-changed callback or you can poll get-state 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 get-tag-id.

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 request-tag-id 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 request-tag-id.

The following symbols are available for this function:

  • tag-type-mifare-classic = 0, for <tag-type>
  • tag-type-type1 = 1, for <tag-type>
  • tag-type-type2 = 2, for <tag-type>
tinkerforge call nfc-rfid-bricklet <uid> get-tag-id
Output:
  • tag-type -- int (has symbols)
  • tid-length -- int
  • tid -- int,int,..4x..,int

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 request-tag-id.

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

  1. Call request-tag-id
  2. Wait for state to change to RequestTagIDReady (see get-state or state-changed callback)
  3. Call get-tag-id

The following symbols are available for this function:

  • tag-type-mifare-classic = 0, for tag-type
  • tag-type-type1 = 1, for tag-type
  • tag-type-type2 = 2, for tag-type
tinkerforge call nfc-rfid-bricklet <uid> get-state
Output:
  • state -- int (has symbols)
  • idle -- bool

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 request-page, 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 get-page.

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

The following symbols are available for this function:

  • state-initialization = 0, for state
  • state-idle = 128, for state
  • state-error = 192, for state
  • state-request-tag-id = 2, for state
  • state-request-tag-id-ready = 130, for state
  • state-request-tag-id-error = 194, for state
  • state-authenticating-mifare-classic-page = 3, for state
  • state-authenticating-mifare-classic-page-ready = 131, for state
  • state-authenticating-mifare-classic-page-error = 195, for state
  • state-write-page = 4, for state
  • state-write-page-ready = 132, for state
  • state-write-page-error = 196, for state
  • state-request-page = 5, for state
  • state-request-page-ready = 133, for state
  • state-request-page-error = 197, for state
tinkerforge call nfc-rfid-bricklet <uid> authenticate-mifare-classic-page <page> <key-number> <key>
Parameters:
  • <page> -- int
  • <key-number> -- int (has symbols)
  • <key> -- int,int,..3x..,int
Output:

no output

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 request-tag-id
  2. Wait for state to change to RequestTagIDReady (see get-state or state-changed callback)
  3. If looking for a specific tag then call get-tag-id and check if the expected tag was found, if it was not found go back to step 1
  4. Call authenticate-mifare-classic-page with page and key for the page
  5. Wait for state to change to AuthenticatingMifareClassicPageReady (see get-state or state-changed callback)
  6. Call request-page or write-page to read/write page

The following symbols are available for this function:

  • key-a = 0, for <key-number>
  • key-b = 1, for <key-number>
tinkerforge call nfc-rfid-bricklet <uid> write-page <page> <data>
Parameters:
  • <page> -- int
  • <data> -- int,int,..13x..,int
Output:

no output

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 request-tag-id
  2. Wait for state to change to RequestTagIDReady (see get-state or state-changed callback)
  3. If looking for a specific tag then call get-tag-id and check if the expected tag was found, if it was not found got back to step 1
  4. Call write-page with page number and data
  5. Wait for state to change to WritePageReady (see get-state or state-changed callback)

If you use a Mifare Classic tag you have to authenticate a page before you can write to it. See authenticate-mifare-classic-page.

tinkerforge call nfc-rfid-bricklet <uid> request-page <page>
Parameters:
  • <page> -- int
Output:

no output

Reads 16 bytes starting from the given page and stores them into a buffer. The buffer can then be read out with get-page. 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 request-tag-id
  2. Wait for state to change to RequestTagIDReady (see get-state or state-changed callback)
  3. If looking for a specific tag then call get-tag-id and check if the expected tag was found, if it was not found got back to step 1
  4. Call request-page with page number
  5. Wait for state to change to RequestPageReady (see get-state or state-changed callback)
  6. Call get-page 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 authenticate-mifare-classic-page.

tinkerforge call nfc-rfid-bricklet <uid> get-page
Output:
  • data -- int,int,..13x..,int

Returns 16 bytes of data from an internal buffer. To fill the buffer with specific pages you have to call request-page beforehand.

Advanced Functions

tinkerforge call nfc-rfid-bricklet <uid> get-identity
Output:
  • uid -- string
  • connected-uid -- string
  • position -- char
  • hardware-version -- int,int,int
  • firmware-version -- int,int,int
  • device-identifier -- int (has symbols)

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

Callbacks

Callbacks can be used to receive time critical or recurring data from the device:

tinkerforge dispatch nfc-rfid-bricklet <uid> example

The available callbacks 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.

tinkerforge dispatch nfc-rfid-bricklet <uid> state-changed
Output:
  • state -- int (has symbols)
  • idle -- bool

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

The following symbols are available for this function:

  • state-initialization = 0, for state
  • state-idle = 128, for state
  • state-error = 192, for state
  • state-request-tag-id = 2, for state
  • state-request-tag-id-ready = 130, for state
  • state-request-tag-id-error = 194, for state
  • state-authenticating-mifare-classic-page = 3, for state
  • state-authenticating-mifare-classic-page-ready = 131, for state
  • state-authenticating-mifare-classic-page-error = 195, for state
  • state-write-page = 4, for state
  • state-write-page-ready = 132, for state
  • state-write-page-error = 196, for state
  • state-request-page = 5, for state
  • state-request-page-ready = 133, for state
  • state-request-page-error = 197, for state