force restart by PN532

Hi all,

I build my own stand alone board of ATMEGA328-PU with the PN532 nfc reader, on each time I tap the phone (smart phone with NFC) the board is restarting?!!!
it is seems like to be an interference between the NFC field of the phone and the controller cycle, how to avoid this?!

any help appreciated.

My first guess is insufficient power supply filtering, so when the radio turns on, the voltage droops and and the chip resets. Put a capacitor between Vcc and Gnd if you don’t have one already, something in the 10-100uf range.

Also, on that note, some standalone arduino instructions leave out the 0.1uf ceramic caps for decoupling that should be placed between gnd and vcc, and gnd and avcc, as close to the chip as possible. These are necessary for reliable operation. No matter what, these should be there (you should have 0.1uf decoupling caps between supply and ground for any IC - many of them need it).

Of course, there could also be a bug in the code you haven’t shown us where you’re doing something wrong that makes the chip reset when it gets data from the NFC reader, or there could be some other flaw in the schematics you haven’t posted that is causing the problem.