My Galaxy 5 has strange behaviour when i'm emulate a card on the ACR122U.
I think the problem occured when i ran an Android update. When the application isn't on the foreground my intent filters doesn't catch the tag anymore because the emulated tag is seen as a JIS 6319-4 instead of a ISO/IEC 14443-4 tag.
The sequence i get when the application isn't on the foreground OR is on the foreground and running in foregroundDispatch:
TgInitAsTarget
> FF 00 00 00 27 D4 8C 04 04 00 01 23 45 20 000000000000000000000000000000000000000000000000000000000000
< D5 8D 08 E0 80 90 00
TgGetData
> FF 00 00 00 02 D4 86
Target has been released error
< D5 87 29 90 00
I loop this 5 times, but none of the TgInitAsTarget will work. When i'm using enableReaderMode (without NDEF skip) i get the correct sequence:
...
> FF 00 00 00 02 D4 86 //TgGetData
< D5 87 00 00 A4 04 00 07 D2 76 00 00 85 01 01 00 9000 //SELECT command
> FF 00 00 00 05 D4 8E 02 6A 82 //file or application not found
< D5 8F 00 90 00 //Ack
> FF 00 00 00 02 D4 86 //TgGetData
< D5 87 00 00 A4 04 00 07 D2 76 00 00 85 01 00 90 00 //SELECT command
> FF 00 00 00 05 D4 8E 02 6A 82 //file or application not found
< D5 8F 00 90 00 //Ack
> FF 00 00 00 02 D4 86 //TgGetData
< D5 87 00 00 A4 04 00 07 D2 76 00 00 85 01 00 90 00 //SELECT command
> FF 00 00 00 05 D4 8E 02 6A 82 //file or application not found
< D5 8F 00 90 00 //Ack
TgGetData
> FF 00 00 00 02 D4 86
//Recieving data
Question 1
Why does Android send nothing back when the application isn't on the foreground or with enableForegroundDispatch? It's very weird because it was always working, but it looks like the update changed the behaviour of NFC.
Question 2
Is it normal that the behaviour of enableReaderMode (without NDEF skip) is different from the behaviour of enableForegroundDispatch?
Note that reader-moder mode is enabled with the following command:
nfcAdapter.enableReaderMode(this, this, NfcAdapter.FLAG_READER_NFC_A, null);
This seems to be a known issue with the PN532 NFC controller. So far I did not find any solution to this. That's the same problem that you already discovered in this question of yours.
Well, as you already found out, the Android device shows that it detects the emulated card as FeliCa. The response to the tgInitAsTarget command (D5 8D 08 E0 80 90 00) indicates, however, that the PN532 was activated as ISO-DEP though. Consequently, it seems that the Android device initiated the communication with the emulated ISO-DEP card but must have immediately dropped it without ever sending command frames (hence you receive the error in response to the tgGetData command). Instead, the Android device must have detected (and possibly talked to) the emulated FeliCa (actually NFCIP-1) card (which relates to the problem in the first part of my answer).
As this was working before, the update must have introduced some changes to the polling/peer-discovery algorithm of your Android device.
That depends on what you consider "normal behavior". As you enabled Android's reader-mode with the command
nfcAdapter.enableReaderMode(this, this, NfcAdapter.FLAG_READER_NFC_A, null);
you explicitly instruct Android to behave differently than with the default tag/peer discovery mechanism (that's used with enableForegroundDispatch and the normal tag dispatch system).
The default polling will try to discover all different tag technologies (NfcA, NfcB, NfcF (fast), NfcF (slow), NfcV (possible with multiple modes), NFCIP-1 active mode, NfcBarcode; usually not in this order), hence it can discover the ACR122U in FeliCa/NFC-DEP mode.
With your enableReaderMode command, you explicitly instruct Android to only poll for NfcA. Hence, your device will properly activate the ACR122U in ISO-DEP mode and, consequently, it will start the NDEF discovery procedure.