From 0f818f53075c8e3f09721b5c352e4b792654e172 Mon Sep 17 00:00:00 2001
From: gilphilbert <gil.philbert@gmail.com>
Date: Sun, 4 Jul 2021 00:21:56 -0700
Subject: [PATCH 1/2] passive read - non blocking

---
 NfcAdapter.cpp                     | 25 +++++++++++++-
 NfcAdapter.h                       |  5 ++-
 examples/ReadTagIRQ/ReadTagIQR.ino | 55 ++++++++++++++++++++++++++++++
 3 files changed, 83 insertions(+), 2 deletions(-)
 create mode 100644 examples/ReadTagIRQ/ReadTagIQR.ino

diff --git a/NfcAdapter.cpp b/NfcAdapter.cpp
index 9099bde..15da978 100644
--- a/NfcAdapter.cpp
+++ b/NfcAdapter.cpp
@@ -1,8 +1,17 @@
 #include <NfcAdapter.h>
 
-NfcAdapter::NfcAdapter(PN532Interface &interface)
+NfcAdapter::NfcAdapter(PN532Interface &interface, uint8_t irqPin = -1)
 {
     shield = new PN532(interface);
+
+    //set the IRQ pin
+    _irqPin = irqPin;
+
+    // if defined, set the pin to input mode
+    if (irqPin > -1)
+    {
+        pinMode(irqPin, INPUT);
+    }
 }
 
 NfcAdapter::~NfcAdapter(void)
@@ -194,6 +203,20 @@ boolean NfcAdapter::write(NdefMessage& ndefMessage)
     return success;
 }
 
+
+boolean NfcAdapter::startPassive()
+{
+    if (_irqPin > -1)
+    {
+        #ifdef NDEF_DEBUG
+        Serial.println(F("IRQ pin not specified"));
+        #endif
+        shield->startPassiveTargetIDDetection(PN532_MIFARE_ISO14443A);
+        return 1;
+    }
+    return 0;
+}
+
 // TODO this should return a Driver MifareClassic, MifareUltralight, Type 4, Unknown
 // Guess Tag Type by looking at the ATQA and SAK values
 // Need to follow spec for Card Identification. Maybe AN1303, AN1305 and ???
diff --git a/NfcAdapter.h b/NfcAdapter.h
index 1ef9e59..f55e6cc 100644
--- a/NfcAdapter.h
+++ b/NfcAdapter.h
@@ -22,7 +22,7 @@
 
 class NfcAdapter {
     public:
-        NfcAdapter(PN532Interface &interface);
+        NfcAdapter(PN532Interface &interface, uint8_t irqPin = -1);
 
         ~NfcAdapter(void);
         void begin(boolean verbose=true);
@@ -35,9 +35,12 @@ class NfcAdapter {
         boolean format();
         // reset tag back to factory state
         boolean clean();
+        // enter passive detection mode (IRQ). For use with I2C ONLY.
+        boolean startPassive();
     private:
         PN532* shield;
         byte uid[7];  // Buffer to store the returned UID
+        uint8_t _irqPin; // stores the IRQ pin for I2C mode
         unsigned int uidLength; // Length of the UID (4 or 7 bytes depending on ISO14443A card type)
         unsigned int guessTagType();
 };
diff --git a/examples/ReadTagIRQ/ReadTagIQR.ino b/examples/ReadTagIRQ/ReadTagIQR.ino
new file mode 100644
index 0000000..6c12d3e
--- /dev/null
+++ b/examples/ReadTagIRQ/ReadTagIQR.ino
@@ -0,0 +1,55 @@
+#include <Wire.h>
+#include "PN532_I2C.h"
+#include "PN532.h"
+#include "NfcAdapter.h"
+#include "PN532Interface.h"
+
+#define CARD_DELAY    1000
+#define IRQ_PIN       14
+
+// IRQ only works in I2C mode for the PN532
+PN532_I2C pn532_i2c(Wire);
+NfcAdapter nfc = NfcAdapter(pn532_i2c, IRQ_PIN);
+
+long lastRead = 0;
+bool enabled = true;
+int irqCurr;
+int irqPrev;
+
+void irqListen() {
+  irqPrev = irqCurr = HIGH;
+  nfc.startPassive();
+  Serial.println("\nScan a NFC tag\n");
+}
+
+void readCard() {
+  if (nfc.tagPresent()) {
+    NfcTag tag = nfc.read();
+    tag.print();
+    lastRead = millis();
+  }
+  enabled = false;
+}
+
+void setup () {
+  Serial.begin(9600);
+  nfc.begin();
+  irqListen();
+}
+
+void loop () {
+  if (!enabled) {
+    if (millis() - lastRead > CARD_DELAY) {
+      enabled = true;
+      irqListen();
+    }
+  } else {
+    irqCurr = digitalRead(IRQ_PIN);
+
+    if (irqCurr == LOW && irqPrev == HIGH) {
+      readCard();
+    }
+  
+    irqPrev = irqCurr;
+  }
+}
\ No newline at end of file

From 201dac1f9e755e8e67b3b48090cd6d6856fde5de Mon Sep 17 00:00:00 2001
From: gilphilbert <gil.philbert@gmail.com>
Date: Mon, 5 Jul 2021 10:28:41 -0700
Subject: [PATCH 2/2] simplify i2c irq example

---
 NfcAdapter.cpp                     |  2 +-
 examples/ReadTagIRQ/ReadTagIQR.ino | 17 +++++++++++------
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/NfcAdapter.cpp b/NfcAdapter.cpp
index 15da978..d279b25 100644
--- a/NfcAdapter.cpp
+++ b/NfcAdapter.cpp
@@ -1,6 +1,6 @@
 #include <NfcAdapter.h>
 
-NfcAdapter::NfcAdapter(PN532Interface &interface, uint8_t irqPin = -1)
+NfcAdapter::NfcAdapter(PN532Interface &interface, uint8_t irqPin)
 {
     shield = new PN532(interface);
 
diff --git a/examples/ReadTagIRQ/ReadTagIQR.ino b/examples/ReadTagIRQ/ReadTagIQR.ino
index 6c12d3e..422f456 100644
--- a/examples/ReadTagIRQ/ReadTagIQR.ino
+++ b/examples/ReadTagIRQ/ReadTagIQR.ino
@@ -1,13 +1,18 @@
+/* -------------------------------------------------------------- */
+/*  This example uses the IRQ port on the PN532 which is only     */
+/*  available when the PN532 is in IRQ mode. It will not work in  */
+/*  other modes. You will need to connect the IRQ pin to an IO    */
+/* -------------------------------------------------------------- */
+
 #include <Wire.h>
 #include "PN532_I2C.h"
 #include "PN532.h"
 #include "NfcAdapter.h"
-#include "PN532Interface.h"
 
-#define CARD_DELAY    1000
-#define IRQ_PIN       14
+//how long to wait between card reads
+#define CARD_DELAY    1000  // wait 1s before reading another card
+#define IRQ_PIN       14    // pin the IRQ on the PN532 is connected to
 
-// IRQ only works in I2C mode for the PN532
 PN532_I2C pn532_i2c(Wire);
 NfcAdapter nfc = NfcAdapter(pn532_i2c, IRQ_PIN);
 
@@ -19,7 +24,7 @@ int irqPrev;
 void irqListen() {
   irqPrev = irqCurr = HIGH;
   nfc.startPassive();
-  Serial.println("\nScan a NFC tag\n");
+  Serial.println("Scan a NFC tag");
 }
 
 void readCard() {
@@ -52,4 +57,4 @@ void loop () {
   
     irqPrev = irqCurr;
   }
-}
\ No newline at end of file
+}