@Javier, thanks for the hint. I did not understood all you tries, but I've verified the followings already:

• resetting arduino
• changing voltage source from 5v to 3.3V

What I do not understand is:

• removing firmware lines of code

@Lokki , thanks for the hint. I've tried the whole range from 9600 up to 250000, but the result is the same.

@Sergey , I think, that we both have the same issue, I've also checked the twi.c and my intention was that my code stopped on the same line. What the hell? Has anybody better understanding of the I2C protocol? Maybe the NFC shield is absolutely not responding to I2C protocol? But, I've 3 NFC shields of the same type but ordered from 3 different shops. The result is the same.... It's very hard to imagine, that all 3 shields are wrong, so the question is, what are we doing wrong?!

@Lokki thanks for your suggestion, but that manual I have earlier than my first NFC shield. What I've understood from that manual I've used while wiring. The sample codes are also from there...
I've checked the document 10 times also the wiring, tried to re-install the libraries, but the result is the same. That's why I've uploaded the photo, maybe you or somebody else has better eyes or more experience, what to check or where to look around...

Hi @Lokki ,
My complaint regarding the NFC shield was accepted by the seller, so I ordered a new board. With this new board I got a step further, the power led is now working, but the card detection still now, the code does not goes through the initialization phase (nfc.begin()), it just holds on that line and never returns. Do you have any idea what could be the problem? I'm absolutely disappointed, as this is the third NFC shield and I'm still at the same stage ...
I'm using I2C communication, the switches were setup based on that (channel 1 on, channel 2 off), see picture below.

Any idea would be really appreciated!

Hi @Lokki, thanks for you answer, I've tried a lot of different ways, how to power the NFC board, but the power led is still off. So, I've decided to open a complain at the store where I've bought the NFC shield, as in my opinion, the power led should at least work, otherwise the shield is non-functional.

Hi all,

I've ordered the same module and fighting with that for more that a week, but without any success. I've the version 3 of the NFC module and WDLduino UNO. I've switched the NFC module to use I2C (switch 1 on, switch 2 off). The problem is, that the sample code does not go through the initialization state, so the loop never starts. Also the initialization does not write that the board is not found, it only hangs. What is also interesting, that the power light on the NFC module is also off.
I've 2 ARDUINOs (the same type) and also two NFC modules (ordered from different stores), but both have the same issue. Do you have any idea, what could be the problem or what else can I check?

Some additional notes: I've turned on the debugging on the NFC library, so I know, that the code is hanging on PN532_I2C::wakeup, the _wire->endTransmission(); never comes back (PN532_I2C.cpp).

Any idea or help would be appreciated.