NFC difficulties

[MStengl]

Trying to create a simple, beginner level NFC read/write app just to figure out the basics.

Started with App inventor pre-made BallShuffle app (NFC game) but it doesn't work well. Receiving a message the tag is empty (attached please see App_msg1 phone screenshot). The app is downloaded as the "apk" file (not working in the dev/test environment.

Created simple test app (write/read button) and it does read and write but during the read session it throws a Runtime error (image App_msg2) attached) saying that "API can not be called while activity is paused" ?  

I do not use any API in my super simple read/write test application

It reads/writes to NTAG213 but can't do it with NTAG216

Available documentation on the App Inventor 2 site is not sufficient for me to figure out what I am doing wrong.

Any help in form of an working app, direction to a good paper about the NFC for App Inventor or any other suggestion is more than welcome.

I use Android Samsung S3 with 5Gb of free memory space.

Reinstalled App inventor on it, cleared cash, reset all connections, reload the apps etc.. - no luck

Thank you in advance for your feedback

 Milan

[Abraham Getzler]

Is the Ball Shuffle app the same as the Cup Game?

http://explore.appinventor.mit.edu/ai2/cup-game

Post a downloaded blocks image for more ideas.

ABG

[Abraham Getzler]

It reads/writes to NTAG213 but can't do it with NTAG216

Factor out AI2 and try a different NFC app -

See this thread ...

https://forums.oneplus.net/threads/nfc-tags-read-but-no-write-ntag216.390996/

ABG

 

[MStengl]

Hi ABG, 

Yes, the Ball Shuffle app is the same app as the Cup Game [http://explore.appinventor.mit.edu/ai2/cup-game ]

I am in process of posting the "aia" of my test app, screens of the blocks involved and also the designer's view of the same.

Started to think that I might need:

A) some time delay between switching from the "read" to "write" 

B) some mechanism to "control" interruptions that could occur while my app is working with the NFC 

Thank you for your feedback 

 Milan

P.S. learning this interface, trying to attach the rest...

[MStengl]

OK, good idea.

Will test different NFC apps and different tags to see if it happens with any other combination.

Than will post here and turn back to my test app

Milan

[Abraham Getzler]

Is your new tag type text-only?

Note the disclaimer at http://ai2.appinventor.mit.edu/reference/components/sensors.html#NearField

ABG

[MStengl]

Not sure about the tag type, Downloading some NFC "tools" to see "deeper" into the tags' structure. I thought it is just a memory space (generally an address space of a defined size) and it would depend only on what one writes into it. From the data structure entered - yes, I am entering only text. Will post back after I "scan" the tags for their structure 

[MStengl]

Downloaded an "api" file from this forum from an user who reported similar issues in 2013 (the original post is closed but I attached the app - called NFCtest3). His app will try to write but will throw the "empty tag" message in that process and also a nasty Run-Time error (android phone screen shot attached in jpg).  Tag specs (of the tag used in this scenario) are below (acquired with an NFC scan tool). The further I go with testing the more errors are coming up.

Working on finding a stable application that can consistently write / read - just to weed out possible bad tags and start with MIT App Inventor NFC feature testing. 

[MStengl]

Tag Specs attached this time.

Note: the android phone screen shot is from my phone (today) after I run other forum member's app (downloaded from a 2013 post)

TAG USED - SPECS:

Manufacturer: NXP Semiconductors

IC Type = NTAG213

NFC Forum NDEF-compliant tag = Type 2 Tag

Capacitance = 50pF

Protocol = ISO/IEC 14443-3

Encoding = UTF-8

[Abraham Getzler]

Maybe some manufacturer NFC reader apps from the Play Store might help

with the finger pointing.

What do they say about your reader and tags?

ABG

[Abraham Getzler]

For that error, did you fix the red triangle error in your blocks before you tried to run it?

See attached.

ABG

[MStengl]

ABG,

no, that was the original App (from 2013) I downloaded to compare. Left it as it was just to run it few times. Will fix the error tonight.

In the meantime I tried 4 free apps (downloaded from the Google Play store) and only 1 can read and write consistently to the 3 tags I am using as a test group (two NTAG216 and one NTAG213). So, that would mean I can exclude the smart device I am using (was thinking I need to update the "OS") and the tags as a root cause for my problems (?)

Basically, back to the AI2 and figuring out what is triggering the problems

Knowing that delays (timers/counters) might not work well in the AI2 I still have a feeling that timing of the "code" and syncing it with phone/tag proximity (bring tags in for read/write + move a phone away when done) are playing a role here. 

Difficult to troubleshoot (trying to figure out appropriate test code I could run step by step)..

[MStengl]

OK, 3rd day.

Searching for the root cause I created a super simple 2 blocsk app. (images attached). One button to enable "read" and color changing block to signal a tag has been read. Created "apk" file and installed it on my cell phone (Android samsung S3)

In addition, I am using one stable NFC write/read app downloaded off of the Google Store which is not showing any issues

Also I decided not to swing and move the phone around but rather;

- place it over (on) the tag

- keep it there, static for a while

- only _then_ interact with my app UI (click the "read" button) to enable the read thread.  Here is what I observed;

1) placed a phone over the tag

2) waited 1/2 -1 sec (before I would touch the 'read' button)

3) before I had a change to touch the UI (the "read" button), the phone interacted with the tag and popped up the message "Empty Tag" ... "unknown tag type"...(attached: Image 1)

4) repeated the above several times and got the same results

At this point I wanted to understand if this is some issue due to the apps I created or tags or the cell phone ? So I continued:

5) shut off my NFC app (that I created), left the cell phone NFC = "ON" and put it over a tag (repeated for several tags)

6) received the same "Empty Tag" ".. "Unknown tag type" message for the NTAG216 which had its memory wiped with some "Tag Tool"

7) received a different popup message for NTAG213 and NTAG216 that had some txt on them - asking me whihc app I want to use to interact with them (see Image 2  attached)

Now it seemed clear the issue of the "Empty Tag" messasge was not caused by my apps but rather by the cell phone NFC feature - or better to say by some system level process related to the NFC being set "ON" (in the  PC world I would say - "NFC driver issue" to express what I think is messign up with me here). To conclude I did the following:

8) power cycled the phone, set NFC= OFF, placed the phone on a tag -- > no reaction, nothing

9) set the NFC= ON, placed the phone on a tag -- > got the same messages and behavior described under 6 and 7 above....

Conclusion:
A) Some "default" app / feature (unknown to me), related to my phone's NFC settings (when NFC=ON) coexists with the NFC apps I created and installed and is interacting with the tag, regardles of my installed app (see 5, 6, 7 above). This could help explain intermittent success /error episodes observed previously during read / write sessions.

B) The tags are not the issue (NTAG213, NTAG 216) but the interaction between that NFC generic/built in "process" and my own apps

Now, ideas are needed to find out what that "hidden" process is and how to neutralize it ?

Given the structure of the message presented on the image 2 -

Thank you

  Milan

[MStengl]

Attaching app blocks, just because I referenced them in the above message

[Abraham Getzler]

Two ideas ...

The NFC TagRead event has a message  local variable that ostensibly should contain the

newly arrived message.  You don't show it.  (Too obvious)

Does your phone have a section in its Settings app for control of NFC operations?

That might prove informative.

ABG

[Abraham Getzler]

A search for NFC using this board's search box found this idea ...

https://groups.google.com/forum/?utm_medium=email&utm_source=footer#!searchin/mitappinventortest/nfc|sort:relevance/mitappinventortest/ZW7SihOrPvw/228jx1rioTcJ

The tags only work after they have been initialized by the app mentioned in that post .

ABG

[MStengl]

Thank you ABG.
Saw those posts earlier but only now I think I can interpret them. The phone seems to be behaving as designed (?).

1. The app mentioned in the link you provided is called "Tags" and that is the one which seems to be jumping out every time the NFC is set to ON and a tag is brought close to the phone, regardless of what my own NFC apps are doing.

2. When I bring a pre-formatted tag to the phone, it asks me which of the NFC apps I want to use (sounds OK)

3. When a tag is unformatted or its memory is wiped out - the "Tags" app (in the phone Application Manager menu "ALL") throws the "unknown tag type" messasge

It seems I need to test the following scenarios to conclude this case';

A) Disable that "bult in" app called "Tags" (your link) and record what will change due to that

B) If that helps reduce popups etc - I need to see if I can shut off that app ("Tags") from within my AI2 app to make sure that my app works fine on other phones

C) Figure out a way to create time delays or loops betwen the NFC "actions" - why ? - because it seems the NFC is firing continuously as long as it is set to "ON" on the phone (perhaps it is that app "Tags" making it do so) and also when (within the AI2 app) the "read mode" is set to "true".

It is not clear to me if the NFC "write" event stops automatically wiht the "TagWritten" event or if it continues firing. Also, will the app stop reading after the TagRead event "happens" or does it continue reading untill we set TagRead to False ?

Would you know of any additional literature about the AI2 NFC ?

What is available on the AI2 web site is pretty minimalistic - at least for me.

Thank you for your help so far !

 Milan

[MStengl]

So I turned off that application (Settings - Application Manager / "tab ALL / Tags app --> see attached images) but it didn;t help.

If the NFC =ON and I bring a tag close to the phone it now either makes a sound (in case of an unformatted tag) or opens a window asling me to select which NFC app I want to use (in case of a configured tag).

I downloaded a 3rd party NFC tag which used to be very stable and has only 2 buttons: Read from and Write to the tag. I start the app and am not touching neither button. If I bring a configured tag to the phone, the app suddently reads it without me asking it to do that.

Trying to find how to stop this unwanted behavior because it affects even 3rd party, stable apps by taking the control over the NFC feature.

Looking into apps that are Running (screnshot attached) and the only one that seems suspicious to me is the SmartCardService. I don;t see any NFC related app/name ?

[MStengl]

Also, I am trying to understand what is the "WriteType" property and how to use it ?

[Abraham Getzler]

C) Figure out a way to create time delays or loops betwen the NFC "actions" 
- why ? - because it seems the NFC is firing continuously as long as it is 
set to "ON" on the phone (perhaps it is that app "Tags" making it do 
so) and also when (within the AI2 app) the "read mode" is set to "true".

AI2 is event driven, unlike Arduinos .

You should never loop, only respond to events firing.

The only exception is when you are looping thru a data structure.

Otherwise you will freeze the app.

The documentation is indeed sparse...

NearField

Non-visible component to provide NFC capabilities. For now this component supports the reading and writing of text tags only (if supported by the device)

In order to read and write text tags, the component must have its ReadMode property set to True or False respectively.

Note: This component will only work on Screen1 of any App Inventor app.

Properties

LastMessage

ReadMode

TextToWrite

WriteType

Events

TagRead(text message)

Indicates that a new tag has been detected. Currently this is only a plain text tag, as specified in the manifest. See Compiler.java.

TagWritten()

Event for TagWritten

Methods

none

Google is your friend.

ABG

[MStengl]

Some surprising results, at least surprising for me

Set my phone NFC to ON.

Created super simple app to read a tag (images attached).

As you can see- I did not even address the "NearField Read Mode" parameter (not in the app)

Even though the literature says the Read Mode should be set to True/False in order to read/write respectively, my app reads tags just fine. NTAG213 and NTAG216 alike. So, it seems the NFC circuit is firing all the time (set by the phone NFC=ON) and the When Near Field TagRead event works/reads regardless of the Read Mode parameter not being set to True..

Next test  = create a simple write app, without any reference to the "NearField Read Mode" parameter to see if I will be able to write to a tag in that environment. It will be strange if that shows to be possible 

[MStengl]

Forgot to ask - can we activate / disactivate phone's NFC setting from within AI2 app ?

Reading about the Activity Starter but can't tell if it can interact with the OS / Phone Settings ?

[Abraham Getzler]

Forgot to ask - can we activate / disactivate phone's NFC setting from within AI2 app ?

Reading about the Activity Starter but can't tell if it can interact with the OS / Phone Settings ?

Here's a pretty full catalog

Maybe it will answer your question.

https://play.google.com/store/apps/details?id=appinventor.ai_mletsch80.AppInvActivityStarter

ABG