Thanks!! Sometimes it is hard to read instructions... Changing to VIN makes things a lot better, but not perfect. I'd say that I get a successful reading about every other time from a distance between 0-3 cm. According to specs it should be possible to read tags från 5-7 cm. This is using the flat circular tag and the credit card tag provided with the reader. My short empirical study says the credit card version works a little bit better than the circular tag.
But more importantly, and the reason why I bought the PN532, I have an NXP NTAG216 implant in my hand between my thumb and index finger. I got this done a couple of months ago and now I am trying to build something that will actually read it. I first tried with an MFRC522 board which worked just fine with the Photon (through SPI) and read the ordinary tags mentioned above without problems (actually better than currently with the PN532). However only got it to read my NTAG216 once. Which is not good enough of course.
Looking around I found the PN532 on https://dangerousthings.com/shop/simple-pn532/ which specifically states that it is compatible with the NTAG216. Great I figured and bought it. But so far no success. I haven't got it to read my implant tag at all and I feel that it works intermittently with the others. Does anyone have any idea how to "boost power", increase range or something to make it more reliable and able to get the signal through my thick skin!?
Or if not, does anyone have any alternatives that might work better? I found a good post from someone who built his own antenna, only I feel it is a little bit too hard core for me, a mere software developer who happens to like electronics (when it works!). Post at http://www.limpkin.fr/index.php?post/2014/10/07/Using-a-Standard-Coil-for-NFC-Tag-Implant-Reading.
Any help would be much appreciated!
Thanks for your time!
BTW. The implant tag works as I can read and write to it from my Samsung Galaxy S7. Only it is not easy and I have to keep moving my hand around for around 5-10 seconds every time before I find the phone's sweet spot. Better than my experiments, but still not good enough.