PN532 I2C IRQ pin

[r28073]

Hi,

I'd connected the PN532 break-out board via I2C to an Atmel controller.
Is the IRQ pin absolutely required to communicate with the PN532 via I2C?

Can the IRQ pin left unconnected?

I understand the the PN532 Application Note v1.2 that the PN532 gets into "normal mode" by default (with P35 being connected to VDD internally, and with IRQ pin being either low or high).

Thanks

[adafruit_support_rick]

The NFC Shield library uses IRQ as a status indicator. The breakout pulls IRQ high to indicate 'busy'. The library waits for IRQ to go low before doing anything. If you tie IRQ low, you should be OK.

[r28073]

Thanks.

Alternatively I guess that the lib could be modified to ignore the IRQ pin status, right?

Another question: I made a custom board and have left both IRQ and P35 pins unconnected/floating... For the PN532 to start into normal mode (and not EmuJoiner nor RF Field on), is there a specific start-up sequence? I understabnd P35 is connected internally to VDD.

Thanks for your help.

[ktownsend]

It's possible, but you will need to rewrite the I2C code in the library to do this. The IRQ pin was used because it's the easiest way to get the PN532 working reliably and to know when a response is ready.