diff --git a/examples/NimBLE_active_passive_scan/NimBLE_active_passive_scan.ino b/examples/NimBLE_active_passive_scan/NimBLE_active_passive_scan.ino
new file mode 100644
index 0000000..9dceb4e
--- /dev/null
+++ b/examples/NimBLE_active_passive_scan/NimBLE_active_passive_scan.ino
@@ -0,0 +1,48 @@
+/*
+ * NimBLE Scan active/passive switching demo
+ *
+ * Demonstrates the use of the scan callbacks while alternating between passive and active scanning.
+ */
+
+#include "NimBLEDevice.h"
+int scanTime = 5 * 1000; // In milliseconds, 0 = scan forever
+BLEScan* pBLEScan;
+
+bool active = false;
+
+class scanCallbacks: public NimBLEScanCallbacks {
+
+    void onDiscovered(NimBLEAdvertisedDevice* advertisedDevice) {
+      Serial.printf("Discovered Advertised Device: %s \n", advertisedDevice->toString().c_str());
+    }
+
+    void onResult(NimBLEAdvertisedDevice* advertisedDevice) {
+      Serial.printf("Advertised Device Result: %s \n", advertisedDevice->toString().c_str());
+    }
+
+    void onScanEnd(NimBLEScanResults results){
+        Serial.println("Scan Ended");
+        active = !active;
+        pBLEScan->setActiveScan(active);
+        Serial.printf("scan start, active = %u\n", active);
+        pBLEScan->start(scanTime);
+    }
+};
+
+
+
+void setup() {
+  Serial.begin(115200);
+  Serial.println("Scanning...");
+
+  NimBLEDevice::init("");
+  pBLEScan = NimBLEDevice::getScan();
+  pBLEScan->setScanCallbacks(new scanCallbacks());
+  pBLEScan->setActiveScan(active);
+  pBLEScan->setInterval(100);
+  pBLEScan->setWindow(99);
+  pBLEScan->start(scanTime);
+}
+
+void loop() {
+}
diff --git a/src/NimBLEAdvertisedDevice.cpp b/src/NimBLEAdvertisedDevice.cpp
index 0c38ca4..3ef71f5 100644
--- a/src/NimBLEAdvertisedDevice.cpp
+++ b/src/NimBLEAdvertisedDevice.cpp
@@ -33,7 +33,7 @@ NimBLEAdvertisedDevice::NimBLEAdvertisedDevice() :
 {
     m_advType          = 0;
     m_rssi             = -9999;
-    m_callbackSent     = false;
+    m_callbackSent     = 0;
     m_timestamp        = 0;
     m_advLength        = 0;
 } // NimBLEAdvertisedDevice
diff --git a/src/NimBLEAdvertisedDevice.h b/src/NimBLEAdvertisedDevice.h
index cb23208..5b7a69f 100644
--- a/src/NimBLEAdvertisedDevice.h
+++ b/src/NimBLEAdvertisedDevice.h
@@ -164,7 +164,7 @@ private:
     uint8_t         m_advType;
     int             m_rssi;
     time_t          m_timestamp;
-    bool            m_callbackSent;
+    uint8_t         m_callbackSent;
     uint8_t         m_advLength;
 #if CONFIG_BT_NIMBLE_EXT_ADV
     bool            m_isLegacyAdv;
diff --git a/src/NimBLEScan.cpp b/src/NimBLEScan.cpp
index d907c54..c7ee07a 100644
--- a/src/NimBLEScan.cpp
+++ b/src/NimBLEScan.cpp
@@ -135,7 +135,12 @@ int NimBLEScan::handleGapEvent(ble_gap_event* event, void* arg) {
                                          event_type == BLE_HCI_ADV_RPT_EVTYPE_SCAN_RSP));
 
             if (pScan->m_pScanCallbacks) {
-                if (pScan->m_scan_params.filter_duplicates && advertisedDevice->m_callbackSent) {
+                if (advertisedDevice->m_callbackSent == 0 || !pScan->m_scan_params.filter_duplicates) {
+                    advertisedDevice->m_callbackSent = 1;
+                    pScan->m_pScanCallbacks->onDiscovered(advertisedDevice);
+                }
+
+                if (pScan->m_scan_params.filter_duplicates && advertisedDevice->m_callbackSent >= 2) {
                     return 0;
                 }
 
@@ -145,16 +150,16 @@ int NimBLEScan::handleGapEvent(ble_gap_event* event, void* arg) {
                   (advertisedDevice->getAdvType() != BLE_HCI_ADV_TYPE_ADV_IND &&
                    advertisedDevice->getAdvType() != BLE_HCI_ADV_TYPE_ADV_SCAN_IND))
                 {
-                    advertisedDevice->m_callbackSent = true;
+                    advertisedDevice->m_callbackSent = 2;
                     pScan->m_pScanCallbacks->onResult(advertisedDevice);
 
                 // Otherwise, wait for the scan response so we can report the complete data.
                 } else if (isLegacyAdv && event_type == BLE_HCI_ADV_RPT_EVTYPE_SCAN_RSP) {
-                    advertisedDevice->m_callbackSent = true;
+                    advertisedDevice->m_callbackSent = 2;
                     pScan->m_pScanCallbacks->onResult(advertisedDevice);
                 }
                 // If not storing results and we have invoked the callback, delete the device.
-                if(pScan->m_maxResults == 0 && advertisedDevice->m_callbackSent) {
+                if(pScan->m_maxResults == 0 && advertisedDevice->m_callbackSent >= 2) {
                     pScan->erase(advertisedAddress);
                 }
             }
@@ -165,16 +170,6 @@ int NimBLEScan::handleGapEvent(ble_gap_event* event, void* arg) {
             NIMBLE_LOGD(LOG_TAG, "discovery complete; reason=%d",
                         event->disc_complete.reason);
 
-            // If a device advertised with scan response available and it was not received
-            // the callback would not have been invoked, so do it here.
-            if(pScan->m_pScanCallbacks) {
-                for(auto &it : pScan->m_scanResults.m_advertisedDevicesVector) {
-                    if(!it->m_callbackSent) {
-                        pScan->m_pScanCallbacks->onResult(it);
-                    }
-                }
-            }
-
             if(pScan->m_maxResults == 0) {
                 pScan->clearResults();
             }
diff --git a/src/NimBLEScan.h b/src/NimBLEScan.h
index 9bf11bb..f0edcaa 100644
--- a/src/NimBLEScan.h
+++ b/src/NimBLEScan.h
@@ -104,13 +104,23 @@ private:
 class NimBLEScanCallbacks {
 public:
     virtual ~NimBLEScanCallbacks() {}
+
     /**
-     * @brief Called when a new scan result is detected.
-     *
-     * As we are scanning, we will find new devices.  When found, this call back is invoked with a reference to the
-     * device that was found.  During any individual scan, a device will only be detected one time.
+     * @brief Called when a new device is discovered, before the scan result is received (if applicable).
+     * @param [in] advertisedDevice The device which was discovered.
+     */
+    virtual void onDiscovered(NimBLEAdvertisedDevice* advertisedDevice) {};
+
+    /**
+     * @brief Called when a new scan result is complete, including scan response data (if applicable).
+     * @param [in] advertisedDevice The device for which the complete result is available.
      */
     virtual void onResult(NimBLEAdvertisedDevice* advertisedDevice) {};
+
+    /**
+     * @brief Called when a scan operation ends.
+     * @param [in] scanResults The results of the scan that ended.
+     */
     virtual void onScanEnd(NimBLEScanResults scanResults) {};
 };