Tag Emulation Write Occurred!

[tmckenna-1]

Hello, I am trying to use an Adafruit PN532 in Emulation mode to trigger a locking mechanism. Basically, the idea is when a write to the emulated tag occurs via a mobile device, the PN532 signals an Arduino which triggers the lock to open. I am running into an issue however, where once a write occurs to the module, that one write triggers the Arduino for every loop (i. e. the lock will open even when a write does not occur, if a write has occurred previously). Any idea on how I can fix this? My code is attached below:

//libraries
#include "emulatetag.h"
#include "NdefMessage.h"

#include <SPI.h>
#include <PN532_SPI.h>
#include "PN532.h"

//defines RELAY pin - can be whatever pin necessary
int RELAY = 5;

//initializes PN 532 with SS pin denoted as pin 10
PN532_SPI pn532spi(SPI, 10);
EmulateTag nfc(pn532spi);

//Sets limit for message at 120 bytes
//Initializes message size
uint8_t ndefBuf[120];
NdefMessage message;
int messageSize;

//Creates 3 byte Unique Identifier for emulated tag
uint8_t uid[3] = {0x12, 0x34, 0x56};

void setup()
{
Serial.begin(115200);
Serial.println("------- Emulate Tag --------");

pinMode(RELAY, OUTPUT);

//Creates NDEF message
message = NdefMessage();

//Record of message - can add anything here (text, URL, etc.)
message.addUriRecord("");
messageSize = message.getEncodedSize();

//Ensures message is smaller than 120 bytes
if (messageSize > sizeof(ndefBuf))
{
Serial.println("ndefBuf is too small");
while (1)
{
}
}

Serial.print("Ndef encoded message size: ");
Serial.println(messageSize);

//encodes message to board
message.encode(ndefBuf);

// comment out this command for no ndef message
nfc.setNdefFile(ndefBuf, messageSize);

// uid must be 3 bytes
nfc.setUid(uid);

nfc.init();
}

void loop()
{
digitalWrite(RELAY, LOW);

//overrides ndef in case a write to this tag occured
nfc.setNdefFile(ndefBuf, messageSize);

Serial.println("Emulate");

// start emulation with timeout
if(!nfc.emulate(3000)){ // timeout 3 second
Serial.println("timed out");
}

//when the tag is written by some outside entity (in this case a mobile phone)
if (nfc.writeOccured())
{
Serial.println("\nWrite occured !");
uint8_t *tag_buf;
uint16_t length;

//signals relay for 0.5 seconds, releasing lock
digitalWrite(RELAY, HIGH);
delay(500);

}
}

[tmckenna-1]

Update: As a temporary fix, I've added in some code so that the Arduino resets itself when a write has occurred. This works in clearing the write to the NFC, but I'd still like a cleaner solution if anyone has any suggestions.

[Cincinnatu]

Can you provide some more information and your new code? I will take a look at the issue soon.

[Lesords]

Hello,

I'm going to close this issue, feel free to re-open it if you have any other questions.

[Autocommentary]