diff --git a/src/espmega_iot_core.cpp b/src/espmega_iot_core.cpp
index f61b243..36aca44 100644
--- a/src/espmega_iot_core.cpp
+++ b/src/espmega_iot_core.cpp
@@ -32,11 +32,16 @@ WebServer otaserver(80);
 #endif
 bool standalone = true;
 char MQTT_BASE_TOPIC[20];
+char AVAILABILITY_TOPIC[40];
 uint8_t base_topic_length = 0;
 char STATE_REQUEST_TOPIC[40];
 bool MQTT_USE_AUTH = false;
 char MQTT_USERNAME[32];
 char MQTT_PASSWORD[32];
+#ifdef ENABLE_WEBUI
+char WEBUI_USERNAME[32];
+char WEBUI_PASSWORD[32];
+#endif
 uint8_t utc_offset = 7;
 #ifdef ENABLE_CLIMATE_MODULE
 float current_room_temp = 0;
@@ -133,6 +138,8 @@ char DAC_VALUE_TOPIC[75];
 #define EEPROM_ADDRESS_ADC_REPORT_STATE 187 // 8bytes, thru 194
 #define EEPROM_ADDRESS_DAC_STATE 195        // 4bytes, thru 198
 #define EEPROM_ADDRESS_DAC_VALUE 199        // 8bytes, thru 206
+#define EEPROM_ADDRESS_WEBUI_USERNAME 207   // 32bytes, thru 238
+#define EEPROM_ADDRESS_WEBUI_PASSWORD 239   // 32bytes, thru 270
 
 char PWM_STATE_TOPIC[75];
 char PWM_VALUE_TOPIC[75];
@@ -176,6 +183,9 @@ void setup()
   Wire.setClock(400000);
 #endif
   io_begin();
+#ifdef VIRTUAL_INTERRUPT_PRELOAD
+  virtual_interrupt_preload();
+#endif
   eeprom_retrieve_init();
   user_pre_init();
 #ifdef ENABLE_INTERNAL_LCD
@@ -239,6 +249,18 @@ void loop()
  */
 void eeprom_retrieve_init()
 {
+  #ifdef ENABLE_WEBUI
+  ESPMega_FRAM.read(EEPROM_ADDRESS_WEBUI_USERNAME, (uint8_t *)WEBUI_USERNAME, 32);
+  ESPMega_FRAM.read(EEPROM_ADDRESS_WEBUI_PASSWORD, (uint8_t *)WEBUI_PASSWORD, 32);
+  if(strlen(WEBUI_USERNAME)==0) {
+    strcpy(WEBUI_USERNAME,"admin");
+    ESPMega_FRAM.write(EEPROM_ADDRESS_WEBUI_USERNAME, (uint8_t *)WEBUI_USERNAME, 32);
+  }
+  if(strlen(WEBUI_PASSWORD)==0) {
+    strcpy(WEBUI_PASSWORD,"admin");
+    ESPMega_FRAM.write(EEPROM_ADDRESS_WEBUI_PASSWORD, (uint8_t *)WEBUI_PASSWORD, 32);
+  }
+  #endif
 // EEPROM Data Retrival
 #ifdef ENABLE_CLIMATE_MODULE
   ac_mode = ESPMega_FRAM.read8(EEPROM_ADDRESS_AC_MODE);
@@ -322,6 +344,8 @@ void eeprom_retrieve_init()
   strcat(PWM_VALUE_TOPIC, "/pwm/00/value");
   memcpy(INPUTS_TOPIC, MQTT_BASE_TOPIC, 20);
   strcat(INPUTS_TOPIC, "/input/00");
+  memcpy(AVAILABILITY_TOPIC, MQTT_BASE_TOPIC, 20);
+  strcat(AVAILABILITY_TOPIC, "/availability");
 #ifdef ENABLE_ANALOG_MODULE
   memcpy(ADC_COMMAND_TOPIC, MQTT_BASE_TOPIC, 20);
   strcat(ADC_COMMAND_TOPIC, "/adc/00/set/state");
@@ -363,6 +387,8 @@ void ota_begin()
 {
   otaserver.on("/", HTTP_GET, []()
                {
+    if(!otaserver.authenticate(WEBUI_USERNAME, WEBUI_PASSWORD))
+      return otaserver.requestAuthentication();
     otaserver.sendHeader("Connection", "close");
     String otabuffer = ota_part1;
     otabuffer+=ota_part2_1+"Hostname"+ota_part2_2+String(HOSTNAME)+ota_part2_3;
@@ -380,6 +406,8 @@ void ota_begin()
     otaserver.send(200, "text/html", otabuffer); });
   otaserver.on("/config", HTTP_GET, []()
                {
+    if(!otaserver.authenticate(WEBUI_USERNAME, WEBUI_PASSWORD))
+      return otaserver.requestAuthentication();
     otaserver.sendHeader("Connection", "close");
     String configbuffer = config_part1;
     configbuffer+=config_txt_part1+"IP Address"+config_txt_part2+"text"+config_txt_part3+"dev_ip"+config_txt_part4+"dev_ip"+config_txt_part5+IP.toString()+config_txt_part6;
@@ -393,11 +421,15 @@ void ota_begin()
     configbuffer+=config_txt_part1+"BMS Server - Username"+config_txt_part2+"text"+config_txt_part3+"bms_username"+config_txt_part4+"bms_username"+config_txt_part5+String(MQTT_USERNAME)+config_txt_part6;
     configbuffer+=config_txt_part1+"BMS Server - Password"+config_txt_part2+"password"+config_txt_part3+"bms_password"+config_txt_part4+"bms_password"+config_txt_part5+String(MQTT_PASSWORD)+config_txt_part6;
     configbuffer+=config_txt_part1+"BMS Server - Endpoint"+config_txt_part2+"text"+config_txt_part3+"bms_endpoint"+config_txt_part4+"bms_endpoint"+config_txt_part5+String(MQTT_BASE_TOPIC)+config_txt_part6;
+    configbuffer+=config_txt_part1+"WebUI Username"+config_txt_part2+"text"+config_txt_part3+"webui_username"+config_txt_part4+"webui_username"+config_txt_part5+String(WEBUI_USERNAME)+config_txt_part6;
+    configbuffer+=config_txt_part1+"WebUI Password"+config_txt_part2+"password"+config_txt_part3+"webui_password"+config_txt_part4+"webui_password"+config_txt_part5+String(WEBUI_PASSWORD)+config_txt_part6;
     configbuffer+=config_part2;
     otaserver.send(200, "text/html", configbuffer); });
 
   otaserver.on("/save_config", HTTP_GET, []()
                {
+    if(!otaserver.authenticate(WEBUI_USERNAME, WEBUI_PASSWORD))
+      return otaserver.requestAuthentication();
     otaserver.sendHeader("Connection", "close");
     String configbuffer = "Configuration Saved. Rebooting . . .";
     otaserver.send(200, "text/html", configbuffer);
@@ -430,6 +462,10 @@ void ota_begin()
       } else if(!arg.compareTo("bms_useauth")) {
         if(!value.compareTo("yes"))
           use_auth = true;
+      } else if(!arg.compareTo("webui_username")) {
+        ESPMega_FRAM.write(EEPROM_ADDRESS_WEBUI_USERNAME, (uint8_t *)value.c_str(), value.length()+1);
+      } else if(!arg.compareTo("webui_password")) {
+        ESPMega_FRAM.write(EEPROM_ADDRESS_WEBUI_PASSWORD, (uint8_t *)value.c_str(), value.length()+1);
       }
     }
       set_mqtt_useauth(use_auth);
@@ -440,6 +476,8 @@ void ota_begin()
   otaserver.on(
       "/update", HTTP_POST, []()
       {
+    if(!otaserver.authenticate(WEBUI_USERNAME, WEBUI_PASSWORD))
+      return otaserver.requestAuthentication();
     otaserver.sendHeader("Connection", "close");
     otaserver.send(200, "text/plain", (Update.hasError()) ? "FAIL" : "OK");
     ESP.restart(); },
@@ -569,13 +607,14 @@ void mqtt_connect()
     Serial.print("MQTT not connected, connecting . . .\n");
     lcd_send_stop_bit();
     if (MQTT_USE_AUTH)
-      mqtt.connect(HOSTNAME, MQTT_USERNAME, MQTT_PASSWORD);
+      mqtt.connect(HOSTNAME, MQTT_USERNAME, MQTT_PASSWORD, AVAILABILITY_TOPIC, 0, true, "offline");
     else
-      mqtt.connect(HOSTNAME);
+      mqtt.connect(HOSTNAME, AVAILABILITY_TOPIC, 0, true, "offline");
     if (mqtt.connected())
     {
       mqtt_subscribe();
       Serial.print("MQTT connected\n");
+      mqtt.publish(AVAILABILITY_TOPIC, "online", true);
       lcd_send_stop_bit();
       publish_pwm_states();
       publish_input_states();
@@ -1798,6 +1837,18 @@ void set_mqtt_useauth(bool use_auth)
   ESPMega_FRAM.write8(EEPROM_ADDRESS_MQTT_USEAUTH, MQTT_USE_AUTH);
 }
 
+void set_webui_username(String username)
+{
+  username.toCharArray(WEBUI_USERNAME, 32);
+  ESPMega_FRAM.write(EEPROM_ADDRESS_WEBUI_USERNAME, (uint8_t *)WEBUI_USERNAME, 32);
+}
+
+void set_webui_password(String password)
+{
+  password.toCharArray(WEBUI_PASSWORD, 32);
+  ESPMega_FRAM.write(EEPROM_ADDRESS_WEBUI_PASSWORD, (uint8_t *)WEBUI_PASSWORD, 32);
+}
+
 /**
  * @brief Resets the device to factory default settings.
  *
@@ -1833,6 +1884,9 @@ void factory_reset()
   set_ip("192.168.0.10");
   set_gw("192.168.0.1");
   set_netmask("255.255.255.0");
+  set_webui_username("admin");
+  set_webui_password("admin");
+
   // Reboot
 #ifdef ENABLE_INTERNAL_LCD
   lcd_send_stop_bit();
@@ -2203,3 +2257,9 @@ bool dac_get_state(int id)
 }
 
 #endif
+
+void virtual_interrupt_preload() {
+  for (int i = 0; i < 16; i++) {
+    virtual_interupt_state[i] = ESPMega_digitalRead(virtual_interrupt_pins[i]);
+  }
+}
\ No newline at end of file
diff --git a/src/espmega_iot_core.hpp b/src/espmega_iot_core.hpp
index f0b63af..bf277ec 100644
--- a/src/espmega_iot_core.hpp
+++ b/src/espmega_iot_core.hpp
@@ -46,6 +46,7 @@
 void mqtt_callback(char* topic, byte* payload, unsigned int length);
 void virtual_interrupt_loop();
 void virtual_interrupt_callback(int pin, int state);
+void virtual_interrupt_preload();
 void network_begin();
 void mqtt_connect();
 void mqtt_subscribe();
diff --git a/src/user_code.hpp b/src/user_code.hpp
index 31f026c..fba970a 100644
--- a/src/user_code.hpp
+++ b/src/user_code.hpp
@@ -12,6 +12,9 @@
 //#define OVERCLOCK_FM
 //#define OVERCLOCK_FM2
 
+// I/O Configuration
+#define VIRTUAL_INTERRUPT_PRELOAD // Preload Virtual Interrupts buffer
+
 // Enable Software Module(s)
 #define ENABLE_INTERNAL_LCD
 #define ENABLE_IR_MODULE