kandi X-RAY | ndef Summary
kandi X-RAY | ndef Summary
A C library for parsing NDEF messages and common NDEF RTDs. NDEF is a message format for NFC communication, and is the primary NFC format understood by Android. Current features - Reading and writing NDEF records. Planned features - Reading and writing text RTD - Reading and writing URI RTD - Reading and writing NDEF messages. Nice-to-have-but-maybe-never-implemented features - Integration with libnfc - Reading and writing other RTDs (Smart Poster, signatures, etc.).
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ndef Key Features
ndef Examples and Code Snippets
Trending Discussions on ndef
I'd like to, at a certain point in an app, request that the user scan an NFC tag. It seems like
enableReaderMode would be a reasonable solution. However, it's not working - consider the following code placed in
onCreate in an Activity in a new Android project (with the NFC permission added).
ANSWERAnswered 2022-Mar-29 at 06:45
You have configured
enableReaderMode to skip Ndef detection BUT you have not configured it to read any other Tag Tech types
NfcAdapter.FLAG_READER_SKIP_NDEF_CHECK you flag options should look like below to be useful to read Tags
I am using Arduino UNO and a PN532 NFC module to receive P2P NDEF messages from an Android phone.
I am sending a plaintext string "Hello". When the transfer is successful, I get this on my Arduino: image
How can I extract the string "Hello" (I think the pairs of numbers before it is the "Hello" in hexadecimal, same for the "text/plain" type indication, type length and payload length) from the NDEF message payload into a regular variable?
Here is my Arduino code:...
ANSWERAnswered 2022-Mar-01 at 18:32
NdefMessage is made up of multiple
NdefRecord items and you
msg has 1 record
so this should do it (not tested)
I would like to store data in an NFC tag in a secure way to avoid copying, but I would like the tag to be affordable and supported by most devices (smartphones).
The NTag21x seems better than the classic Mifare whose algorithm has been corrupted. But is it possible with this one to lock part of the data by leaving an NDef record accessible for reading?
Is the NTag21x secure? I saw that his password was 32bits, it seems easy to break with a dictionary, am I wrong?
On the other hand, after a lot of research I can't really find any detailed documentation on the subject. I don't understand how a reader can tell the difference between the different tags, and what they have in common at the communication protocol level, how to detect a type of tag, know if I can support it in my application. I would like to make a C# / Xamarin application....
ANSWERAnswered 2022-Feb-25 at 18:29
You need to read the datasheet for the tag.
Section 8.5.7 and allows you with the
AUTH0 field to set the first page at which the password is used from.
Thus the first part of the Tag can be readable and later pages can be read/write protected. As long as the tag is big enough to store Ndef message at the beginning of the Tag and your private data at the end of the Tag without using overlapping pages you can achieve free to read and password protected data.
You can also set the
AUTHLIM to set the maximum number of negative password verification attempts so that it is not possible to brute force the password.
To configure these features you need to write to the appropriate memory pages using the low level NfcA
transceive commands detailed in the datasheet.
The biggest problem you have with password protection is if you freely hand out an App that uses the password as it is trivial to reverse engineer the password from the JVM byte code that uses it.
You don't really need to know the different Tags are identified but having a good understanding of how the different levels of protocols and standards fit together is key, this is where this diagram from wikipedia is good.
I am attempting to create an application centered around NFC paired with multiple RFIDs. For this reason I am programming the RFIDs with NDefRecords that open a specific activity in my application. The NdefMessage doing this is as follows...
ANSWERAnswered 2022-Feb-24 at 13:17
You don't seem to be doing any foreground detection, really manifest entries are only used to start your App via NFC if not already running.
If your App is running you should use one of the 2 foreground detection API's, the old an not so reliable
enableForegroundDispatch or the newer and better
Here is an example of how use the better
You can use both of these in conjunction with Manifest filters to handle NFC when your App is and is not running when the NFC Tag is presented.
Also note that your Manifest filter won't trigger for the
NdefFormatable of your write method, your Manifest filter need to filter for
android.nfc.tech.NdefFormatable. See Here for details
I want to pass a text value from my NFC tag to a variable, but want to remove the locale from the text passed to the variable (note, not remove it from the tag).
I am using the nfc_manager package.
Here is the code portion I am using that relates to scanning the tag:...
ANSWERAnswered 2022-Feb-16 at 14:52
The first byte is the length of the characters of the language string
So this should work (my dart is not that good)
for example for the below code is there any tool to see the definition of the function that is decorated?...
ANSWERAnswered 2022-Feb-04 at 11:43
If you intend to see what's the decorator
@app.route() does, the answer lies in Python flask source code. I'm using flask 1.1.2 (the newest stable version currently is 2.0.0), and here is what it's defined in the file
app.py, putting aside the many comments:
I was trying to find a working example of how it is possible to read a message stored on a NDEF tag within the app's active Activity. By far the best I have is such a code:...
ANSWERAnswered 2022-Feb-03 at 18:04
So the normal pattern for NFC in Android is:-
1)When you App is not running an you want it started when a certain type of NFC Tag is presented to the device then you put your
intent-filters in the manifest. Your App then gets started and passed an
Intent that you need to process in your
onCreate method using
2a)Your App is already running in the foreground then you use
enableForegroundDispatch, giving it a pending Intent on what you want to be notified about, this is then processed in
onNewIntent when your App is restarted (paused and resumed) to receive the Intent.
onNewIntent won't get invoked by any manifest entry.
2b)Your App is already running in the foreground then you use
enableReaderMode which is a better replacement for
enableForegroundDispatch, you then process the Tag in
onTagDiscovered which is in a separate thread.
How to process the
Intent received via pattern 1 and 2a is the same, just they need to be called from the correct path in the code that matches the method that triggered the Intent i.e in
onCreate or in
Check out Empty NFC Tag read and write Android Application. Mobile own message returning while scanning Empty Tag but Application not working? for an example of how to use Manifest and
The are also plenty examples of using
enableReaderMode on Stackoverflow as well.
I have make an application for read and write on NFC TAG. But, while I am scanning Empty NFC Tag after opening my application it not responding as I expected as my Application Toast Message "Tag is empty". But, when I close my application then I receiving Mobile belting message.
Basically, I need the help as following:
- Detect Empty NFC Tag from my application.
- Write Server information in that Empty Tag.
- After then reading that information from that Tag.
I am including my code here.
ANSWERAnswered 2022-Feb-01 at 15:29
To handle unformatted Ndef Tags change your "nfc_tech_filter.xml" file to the one below:-
I want to encrypt data in a web browser that is send to my C# backend and decrypted there.
That fails because I am unable to decrypt the data generated on the frontend in the backend.
Here's what I did so far.
First I created a private/public key pair (in XmlString Format). I took the
ExportPublicKey function to generate the public key file from here: https://stackoverflow.com/a/28407693/98491
ANSWERAnswered 2022-Jan-24 at 15:42
You need to encrypt with the private key and then decrypt with the public key
I am trying to write NDEF data to an NFC Tag (Mifare S50 chip) so it can work with my iPhone, I'm using a Raspberry Pi 4 with a RC522 NFC module connected via GPIO and using SPI.
I tried a few approaches to this, and ended up with the code above which didn't seem to write anything to the tag, and it's indeed not readable by my phone, and I think I might be messing up somewhere.
Here's the code:...
ANSWERAnswered 2022-Jan-06 at 01:21
There are two problems with this code.
1)You have created a "stream of bytes" of the ndef message but the SimpleMFRC522 package expects a Unicode String and encodes it to convert it to a "stream of bytes", so basically as it is already a "stream of bytes" it cannot be double encoded.
2)The Mifare S50 chip is a Mifare Classic family chip and these are a proprietary format and don't conform to the NFC Forum Standards and thus don't have a Standards defined way to store Ndef data on them (You need to do more than write a raw set of bytes to the memory to chip for it to be recognised as the data being the Ndef format of data).
For NFC standard compliant/compatible chips there are a number of defined types of how the Ndef data is stored on each type.
While NXP has defined a proprietary way to store Ndef data on a Mifare Classic chip, but the "SimpleMFRC522" is very simple indeed and does not have the code to write the Standard Ndef messages never mind the non standard proprietary methods.
I also note that while the iPhone hardware can read Mifare Classic cards at the low level, I'm not sure it has implemented the Ndef data format on top as well. I do know that some Android phones don't support the proprietary Mifare Classic Hardware at all.
I suggest you read https://www.nxp.com/docs/en/application-note/AN1305.pdf as this is the proprietary format definition on how to store NDEF data on these cards
Unfortunately the RC522 is very old and has limited capabilities and thus is not well supported by more capable Python NFC modules.
You might be better off with https://github.com/ondryaso/pi-rc522 as that at least allows you to write raw bytes.
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