NFC

NFC.on()

Turn NFC on, optionally with a callback function.

// PROTOTYPE
int on(nfc_event_callback_t cb=nullptr);

The callback function has this prototype:

void nfcCallback(nfc_event_type_t type, nfc_event_t* event, void* context);

• type The type of event (described below)
• event The internal event structure (not currently used)
• context An optional context pointer set when the callback is registered (not currently used).

The event types are:

• NFC_EVENT_FIELD_ON NFC tag has detected external NFC field and was selected by an NFC polling device.
• NFC_EVENT_FIELD_OFF External NFC field has been removed.
• NFC_EVENT_READ NFC polling device has read all tag data.

NFC events may occur at interrupt service time. You should not, for example:

• Allocate or free memory (malloc, free, new, delete, strdup, etc.).
• Call Particle functions like Particle.publish()
• Call delay()
• Call Serial.print(), Log.info(), etc.