diff --git a/build.py b/build.py
index 4235c8d7..28319853 100644
--- a/build.py
+++ b/build.py
@@ -29,7 +29,7 @@ haldir = os.path.join (srcdir, "hal")
 halconfig = config.get("board", "halfile")
 halconfigfile = os.path.join (haldir, halconfig)
 if os.path.isfile(halconfigfile) and os.access(halconfigfile, os.R_OK):
-    print "Parsing hardware configuration from " + halconfigfile
+    print("Parsing hardware configuration from " + halconfigfile)
 else:
     sys.exit("Missing file " + halconfigfile + ", please create it! Aborting.")
 
@@ -37,21 +37,21 @@ else:
 lmicconfig = config.get("common", "lmicconfigfile")
 lmicconfigfile = os.path.join (srcdir, lmicconfig)
 if os.path.isfile(lmicconfigfile) and os.access(lmicconfigfile, os.R_OK):
-    print "Parsing LMIC configuration from " + lmicconfigfile
+    print("Parsing LMIC configuration from " + lmicconfigfile)
 else:
     sys.exit("Missing file " + lmicconfigfile + ", please create it! Aborting.")
 
 # check if lora key file is present in source directory
 lorakeyfile = os.path.join (srcdir, config.get("common", "lorakeyfile"))
 if os.path.isfile(lorakeyfile) and os.access(lorakeyfile, os.R_OK):
-    print "Parsing LORAWAN keys from " + lorakeyfile
+    print("Parsing LORAWAN keys from " + lorakeyfile)
 else:
     sys.exit("Missing file " + lorakeyfile + ", please create it! Aborting.")
 
 # check if ota key file is present in source directory
 otakeyfile = os.path.join (srcdir, config.get("common", "otakeyfile"))
 if os.path.isfile(otakeyfile) and os.access(otakeyfile, os.R_OK):
-    print "Parsing OTA keys from " + otakeyfile
+    print("Parsing OTA keys from " + otakeyfile)
 else:
     sys.exit("Missing file " + otakeyfile + ", please create it! Aborting.")
 
@@ -66,7 +66,7 @@ myboard = mykeys["board"]
 myuploadspeed = mykeys["upload_speed"]
 env.Replace(BOARD=myboard)
 env.Replace(UPLOAD_SPEED=myuploadspeed)
-print '\033[94m' + "TARGET BOARD: " + myboard + " @ " + myuploadspeed + "bps" + '\033[0m'
+print('\033[94m' + "TARGET BOARD: " + myboard + " @ " + myuploadspeed + "bps" + '\033[0m')
 
 # parse ota key file
 with open(otakeyfile) as myfile:
@@ -136,4 +136,4 @@ def publish_bintray(source, target, env):
 # put build file name and upload command to platformio environment
 env.Replace(
     PROGNAME="firmware_" + package + "_v%s" % version,
-    UPLOADCMD=publish_bintray)
\ No newline at end of file
+    UPLOADCMD=publish_bintray)
diff --git a/include/globals.h b/include/globals.h
index d76d0e4c..55ee199e 100644
--- a/include/globals.h
+++ b/include/globals.h
@@ -42,8 +42,8 @@
 #define SCREEN_MODE (0x80)
 
 // I2C bus access control
-#define I2C_MUTEX_LOCK() xSemaphoreTake(I2Caccess, pdMS_TO_TICKS(10)) == pdTRUE
-#define I2C_MUTEX_UNLOCK() xSemaphoreGive(I2Caccess)
+#define I2C_MUTEX_LOCK() (xSemaphoreTake(I2Caccess, pdMS_TO_TICKS(2000)) == pdTRUE)
+#define I2C_MUTEX_UNLOCK() (xSemaphoreGive(I2Caccess))
 
 // Struct holding devices's runtime configuration
 typedef struct {
diff --git a/include/irqhandler.h b/include/irqhandler.h
index db5dd2f1..3a06d3da 100644
--- a/include/irqhandler.h
+++ b/include/irqhandler.h
@@ -17,8 +17,8 @@
 #include "timekeeper.h"
 
 void irqHandler(void *pvParameters);
-int mask_user_IRQ();
-int unmask_user_IRQ();
+void mask_user_IRQ();
+void unmask_user_IRQ();
 
 #ifdef HAS_DISPLAY
 void IRAM_ATTR DisplayIRQ();
diff --git a/src/blecsan.cpp b/src/blecsan.cpp
index 1931c788..90761f75 100644
--- a/src/blecsan.cpp
+++ b/src/blecsan.cpp
@@ -146,7 +146,7 @@ IRAM_ATTR void gap_callback_handler(esp_gap_ble_cb_event_t event,
         break;
       }
 
-#if(VENDORFILTER)
+#if (VENDORFILTER)
 
       if ((p->scan_rst.ble_addr_type == BLE_ADDR_TYPE_RANDOM) ||
           (p->scan_rst.ble_addr_type == BLE_ADDR_TYPE_RPA_RANDOM)) {
@@ -162,6 +162,7 @@ IRAM_ATTR void gap_callback_handler(esp_gap_ble_cb_event_t event,
       /* to be improved in vendorfilter if:
       
 
+
       // you can search for elements in the payload using the
       // function esp_ble_resolve_adv_data()
       //
@@ -207,21 +208,21 @@ esp_err_t register_ble_callback(void) {
   ESP_ERROR_CHECK(esp_ble_gap_register_callback(&gap_callback_handler));
 
   static esp_ble_scan_params_t ble_scan_params = {
-      .scan_type = BLE_SCAN_TYPE_PASSIVE,
-      .own_addr_type = BLE_ADDR_TYPE_RANDOM,
+    .scan_type = BLE_SCAN_TYPE_PASSIVE,
+    .own_addr_type = BLE_ADDR_TYPE_RANDOM,
 
-#if(VENDORFILTER)
-      .scan_filter_policy = BLE_SCAN_FILTER_ALLOW_WLIST_PRA_DIR,
+#if (VENDORFILTER)
+    .scan_filter_policy = BLE_SCAN_FILTER_ALLOW_WLIST_PRA_DIR,
   // ADV_IND, ADV_NONCONN_IND, ADV_SCAN_IND packets are used for broadcasting
   // data in broadcast applications (e.g., Beacons), so we don't want them in
   // vendorfilter mode
 #else
-      .scan_filter_policy = BLE_SCAN_FILTER_ALLOW_ALL,
+    .scan_filter_policy = BLE_SCAN_FILTER_ALLOW_ALL,
 #endif
 
-      .scan_interval =
-          (uint16_t)(cfg.blescantime * 10 / 0.625),    // Time = N * 0.625 msec
-      .scan_window = (uint16_t)(BLESCANWINDOW / 0.625) // Time = N * 0.625 msec
+    .scan_interval =
+        (uint16_t)(cfg.blescantime * 10 / 0.625),    // Time = N * 0.625 msec
+    .scan_window = (uint16_t)(BLESCANWINDOW / 0.625) // Time = N * 0.625 msec
   };
 
   ESP_LOGI(TAG, "Set GAP scan parameters");
@@ -234,12 +235,11 @@ esp_err_t register_ble_callback(void) {
 } // register_ble_callback
 
 void start_BLEscan(void) {
-#if(BLECOUNTER)
+#if (BLECOUNTER)
   ESP_LOGI(TAG, "Initializing bluetooth scanner ...");
 
   ESP_ERROR_CHECK(esp_coex_preference_set(
-      (esp_coex_prefer_t)
-          ESP_COEX_PREFER_BALANCE)); // configure Wifi/BT coexist lib
+      ESP_COEX_PREFER_BALANCE)); // configure Wifi/BT coexist lib
 
   // Initialize BT controller to allocate task and other resource.
   btStart();
@@ -254,14 +254,14 @@ void start_BLEscan(void) {
 } // start_BLEscan
 
 void stop_BLEscan(void) {
-#if(BLECOUNTER)
+#if (BLECOUNTER)
   ESP_LOGI(TAG, "Shutting down bluetooth scanner ...");
   ESP_ERROR_CHECK(esp_ble_gap_register_callback(NULL));
   ESP_ERROR_CHECK(esp_bluedroid_disable());
   ESP_ERROR_CHECK(esp_bluedroid_deinit());
   btStop(); // disable bt_controller
-  ESP_ERROR_CHECK(esp_coex_preference_set((
-      esp_coex_prefer_t)ESP_COEX_PREFER_WIFI)); // configure Wifi/BT coexist lib
+  ESP_ERROR_CHECK(esp_coex_preference_set(
+      ESP_COEX_PREFER_WIFI)); // configure Wifi/BT coexist lib
   ESP_LOGI(TAG, "Bluetooth scanner stopped");
 #endif // BLECOUNTER
 } // stop_BLEscan
diff --git a/src/display.cpp b/src/display.cpp
index 0c1a9422..632e0ee8 100644
--- a/src/display.cpp
+++ b/src/display.cpp
@@ -62,8 +62,9 @@ void DisplayKey(const uint8_t *key, uint8_t len, bool lsb) {
 void init_display(const char *Productname, const char *Version) {
 
   // block i2c bus access
-  if (I2C_MUTEX_LOCK()) {
-
+  if (!I2C_MUTEX_LOCK())
+    ESP_LOGW(TAG, "[%0.3f] i2c mutex lock failed", millis() / 1000.0);
+  else {
     // show startup screen
     uint8_t buf[32];
     u8x8.begin();
@@ -141,8 +142,9 @@ void refreshTheDisplay(bool nextPage) {
       myTZ.toLocal(now()); // note: call now() here *before* locking mutex!
 
   // block i2c bus access
-  if (I2C_MUTEX_LOCK()) {
-
+  if (!I2C_MUTEX_LOCK())
+    ESP_LOGW(TAG, "[%0.3f] i2c mutex lock failed", millis() / 1000.0);
+  else {
     // set display on/off according to current device configuration
     if (DisplayIsOn != cfg.screenon) {
       DisplayIsOn = cfg.screenon;
@@ -165,7 +167,9 @@ void draw_page(time_t t, uint8_t page) {
 
   char timeState, buff[16];
   uint8_t msgWaiting;
+#if (HAS_GPS)
   static bool wasnofix = true;
+#endif
 
   // update counter (lines 0-1)
   snprintf(
diff --git a/src/gpsread.cpp b/src/gpsread.cpp
index 1bc8f343..d99a7c46 100644
--- a/src/gpsread.cpp
+++ b/src/gpsread.cpp
@@ -80,11 +80,12 @@ void IRAM_ATTR gps_storetime(gpsStatus_t &gps_store) {
   if (gps.time.isUpdated() && gps.date.isValid() && (gps.time.age() < 1000)) {
 
     // nmea telegram serial delay compensation; not sure if we need this?
-
+    /*
     if (gps.time.age() > nmea_txDelay_ms)
       gps_store.timedate.Second = gps.time.second() + 1;
     else
       gps_store.timedate.Second = gps.time.second();
+    */
 
     gps_store.timedate.Second = gps.time.second();
     gps_store.timedate.Minute = gps.time.minute();
diff --git a/src/hal/generic.h b/src/hal/generic.h
index 280a68ad..9d1d0b4e 100644
--- a/src/hal/generic.h
+++ b/src/hal/generic.h
@@ -53,8 +53,6 @@
 #define HAS_BUTTON (39) // on board button
 #define HAS_RGB_LED (0) // WS2812B RGB LED on GPIO0
 
-#define BOARD_HAS_PSRAM // use extra 4MB extern RAM
-
 // GPS settings
 #define HAS_GPS 1 // use on board GPS
 #define GPS_SERIAL 9600, SERIAL_8N1, GPIO_NUM_12, GPIO_NUM_15 // UBlox NEO 6M
diff --git a/src/irqhandler.cpp b/src/irqhandler.cpp
index f95f6fe9..fabda2f2 100644
--- a/src/irqhandler.cpp
+++ b/src/irqhandler.cpp
@@ -119,18 +119,6 @@ void IRAM_ATTR GpsIRQ() {
 }
 #endif
 
-int mask_user_IRQ() {
-  // begin of time critical section: lock I2C bus to ensure accurate timing
-  if (I2C_MUTEX_LOCK()) {
-    xTaskNotify(irqHandlerTask, MASK_IRQ, eSetBits);
-    return 0;
-  } else
-    return 1; // failure
-}
+void mask_user_IRQ() { xTaskNotify(irqHandlerTask, MASK_IRQ, eSetBits); }
 
-int unmask_user_IRQ() {
-  // end of time critical section: release I2C bus
-  I2C_MUTEX_UNLOCK();
-  xTaskNotify(irqHandlerTask, UNMASK_IRQ, eSetBits);
-  return 0;
-}
\ No newline at end of file
+void unmask_user_IRQ() { xTaskNotify(irqHandlerTask, UNMASK_IRQ, eSetBits); }
\ No newline at end of file
diff --git a/src/lorawan.cpp b/src/lorawan.cpp
index 5507e12b..af8d04bb 100644
--- a/src/lorawan.cpp
+++ b/src/lorawan.cpp
@@ -306,7 +306,7 @@ void onEvent(ev_t ev) {
     break;
 
   case EV_TXSTART:
-    if (!(LMIC.opmode & OP_JOINING))
+    if (!(LMIC.opmode & OP_JOINING)) {
 #if (TIME_SYNC_LORASERVER)
       // if last packet sent was a timesync request, store TX time
       if (LMIC.pendTxPort == TIMEPORT)
@@ -314,6 +314,7 @@ void onEvent(ev_t ev) {
       else
 #endif
         strcpy_P(buff, PSTR("TX START"));
+    }
     break;
 
   case EV_TXCANCELED:
@@ -506,9 +507,15 @@ void IRAM_ATTR user_request_network_time_callback(void *pVoidUserUTCTime,
     return;
   }
 
-  // begin of time critical section: lock I2C bus to ensure accurate timing
-  if (!mask_user_IRQ())
-    return; // failure
+  // begin of time critical section
+
+  // lock I2C bus and application irq to ensure accurate timing
+  mask_user_IRQ();
+  if (!I2C_MUTEX_LOCK()) {
+    ESP_LOGW(TAG, "[%0.3f] Timesync handshake error: i2c bus locking failed",
+             millis() / 1000.0);
+    goto finish; // failure
+  }
 
   // Update userUTCTime, considering the difference between the GPS and UTC
   // time, and the leap seconds until year 2019
@@ -524,7 +531,9 @@ void IRAM_ATTR user_request_network_time_callback(void *pVoidUserUTCTime,
   // Update system time with time read from the network
   setMyTime(*pUserUTCTime + requestDelaySec, 0);
 
-  // end of time critical section: release I2C bus
+finish:
+  // end of time critical section: release I2C bus and app irq
+  I2C_MUTEX_UNLOCK();
   unmask_user_IRQ();
 
 } // user_request_network_time_callback
diff --git a/src/macsniff.cpp b/src/macsniff.cpp
index cd20e39a..0b00e7c1 100644
--- a/src/macsniff.cpp
+++ b/src/macsniff.cpp
@@ -2,7 +2,7 @@
 // Basic Config
 #include "globals.h"
 
-#if(VENDORFILTER)
+#if (VENDORFILTER)
 #include "vendor_array.h"
 #endif
 
@@ -37,33 +37,35 @@ void printKey(const char *name, const uint8_t *key, uint8_t len, bool lsb) {
 }
 
 uint64_t macConvert(uint8_t *paddr) {
-  return ((uint64_t)paddr[0]) | ((uint64_t)paddr[1] << 8) |
-         ((uint64_t)paddr[2] << 16) | ((uint64_t)paddr[3] << 24) |
-         ((uint64_t)paddr[4] << 32) | ((uint64_t)paddr[5] << 40);
+  uint64_t *mac;
+  mac = (uint64_t *)paddr;
+  return (__builtin_bswap64(*mac) >> 8);
 }
 
 bool mac_add(uint8_t *paddr, int8_t rssi, bool sniff_type) {
 
-  char buff[16]; // temporary buffer for printf
+  if (!salt) // ensure we have salt (appears after radio is turned on)
+    return false;
+
+  char buff[10]; // temporary buffer for printf
   bool added = false;
   int8_t beaconID;    // beacon number in test monitor mode
   uint16_t hashedmac; // temporary buffer for generated hash value
-  uint32_t addr2int;  // temporary buffer for shortened MAC
-#if(VENDORFILTER)
-  uint32_t vendor2int; // temporary buffer for Vendor OUI
-#endif
+  uint32_t *mac;      // temporary buffer for shortened MAC
 
   // only last 3 MAC Address bytes are used for MAC address anonymization
-  // but since it's uint32 we take 4 bytes to avoid 1st value to be 0
-  addr2int = ((uint32_t)paddr[2]) | ((uint32_t)paddr[3] << 8) |
-             ((uint32_t)paddr[4] << 16) | ((uint32_t)paddr[5] << 24);
+  // but since it's uint32 we take 4 bytes to avoid 1st value to be 0.
+  // this gets MAC in msb (= reverse) order, but doesn't matter for hashing it.
+  mac = (uint32_t *)(paddr + 2);
+
+#if (VENDORFILTER)
+  uint32_t *oui; // temporary buffer for vendor OUI
+  oui = (uint32_t *)paddr;
 
-#if(VENDORFILTER)
-  vendor2int = ((uint32_t)paddr[2]) | ((uint32_t)paddr[1] << 8) |
-               ((uint32_t)paddr[0] << 16);
   // use OUI vendor filter list only on Wifi, not on BLE
   if ((sniff_type == MAC_SNIFF_BLE) ||
-      std::find(vendors.begin(), vendors.end(), vendor2int) != vendors.end()) {
+      std::find(vendors.begin(), vendors.end(), __builtin_bswap32(*oui) >> 8) !=
+          vendors.end()) {
 #endif
 
     // salt and hash MAC, and if new unique one, store identifier in container
@@ -71,10 +73,9 @@ bool mac_add(uint8_t *paddr, int8_t rssi, bool sniff_type) {
     // https://en.wikipedia.org/wiki/MAC_Address_Anonymization
 
     snprintf(buff, sizeof(buff), "%08X",
-             addr2int + (uint32_t)salt); // convert usigned 32-bit salted MAC
-                                         // to 8 digit hex string
-    hashedmac = rokkit(&buff[3], 5); // hash MAC last string value, use 5 chars
-                                     // to fit hash in uint16_t container
+             *mac + (uint32_t)salt);      // convert unsigned 32-bit salted MAC
+                                          // to 8 digit hex string
+    hashedmac = rokkit(&buff[3], 5);      // hash MAC 8 digit -> 5 digit
     auto newmac = macs.insert(hashedmac); // add hashed MAC, if new unique
     added = newmac.second ? true
                           : false; // true if hashed MAC is unique in container
@@ -88,7 +89,7 @@ bool mac_add(uint8_t *paddr, int8_t rssi, bool sniff_type) {
         blink_LED(COLOR_GREEN, 50);
 #endif
       }
-#if(BLECOUNTER)
+#if (BLECOUNTER)
       else if (sniff_type == MAC_SNIFF_BLE) {
         macs_ble++; // increment BLE Macs counter
 #if (HAS_LED != NOT_A_PIN) || defined(HAS_RGB_LED)
@@ -115,13 +116,14 @@ bool mac_add(uint8_t *paddr, int8_t rssi, bool sniff_type) {
 
     // Log scan result
     ESP_LOGV(TAG,
-             "%s %s RSSI %ddBi -> MAC %s -> Hash %04X -> WiFi:%d  BLTH:%d -> "
+             "%s %s RSSI %ddBi -> salted MAC %s -> Hash %04X -> WiFi:%d  "
+             "BLTH:%d -> "
              "%d Bytes left",
              added ? "new  " : "known",
              sniff_type == MAC_SNIFF_WIFI ? "WiFi" : "BLTH", rssi, buff,
              hashedmac, macs_wifi, macs_ble, getFreeRAM());
 
-#if(VENDORFILTER)
+#if (VENDORFILTER)
   } else {
     // Very noisy
     // ESP_LOGD(TAG, "Filtered MAC %02X:%02X:%02X:%02X:%02X:%02X",
diff --git a/src/main.cpp b/src/main.cpp
index ae883673..f06eb6cd 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -116,10 +116,9 @@ void setup() {
 
   // create some semaphores for syncing / mutexing tasks
   I2Caccess = xSemaphoreCreateMutex(); // for access management of i2c bus
-  if (I2Caccess)
-    xSemaphoreGive(I2Caccess); // Flag the i2c bus available for use
+  assert(I2Caccess != NULL);
 
-    // disable brownout detection
+  // disable brownout detection
 #ifdef DISABLE_BROWNOUT
   // register with brownout is at address DR_REG_RTCCNTL_BASE + 0xd4
   (*((uint32_t volatile *)ETS_UNCACHED_ADDR((DR_REG_RTCCNTL_BASE + 0xd4)))) = 0;
@@ -262,8 +261,8 @@ void setup() {
   // remove bluetooth stack to gain more free memory
   btStop();
   ESP_ERROR_CHECK(esp_bt_mem_release(ESP_BT_MODE_BTDM));
-  ESP_ERROR_CHECK(esp_coex_preference_set((
-      esp_coex_prefer_t)ESP_COEX_PREFER_WIFI)); // configure Wifi/BT coexist lib
+  ESP_ERROR_CHECK(esp_coex_preference_set(
+      ESP_COEX_PREFER_WIFI)); // configure Wifi/BT coexist lib
 #endif
 
 // initialize gps
diff --git a/src/timesync.cpp b/src/timesync.cpp
index 88bc6aa8..35fb8c84 100644
--- a/src/timesync.cpp
+++ b/src/timesync.cpp
@@ -64,7 +64,7 @@ void process_timesync_req(void *taskparameter) {
 
     // wait until we are joined if we are not
     while (!LMIC.devaddr) {
-      vTaskDelay(5000);
+      vTaskDelay(3000);
     }
 
     // collect timestamp samples
@@ -110,10 +110,10 @@ void process_timesync_req(void *taskparameter) {
       }
     } // end of for loop to collect timestamp samples
 
-    // begin of time critical section: lock app irq's and I2C bus
-    if (!mask_user_IRQ()) {
-      ESP_LOGW(TAG,
-               "[%0.3f] Timesync handshake error: irq / i2c masking failed",
+    // lock I2C bus and application irq to ensure accurate timing
+    mask_user_IRQ();
+    if (!I2C_MUTEX_LOCK()) {
+      ESP_LOGW(TAG, "[%0.3f] Timesync handshake error: i2c bus locking failed",
                millis() / 1000.0);
       goto finish; // failure
     }
@@ -135,10 +135,11 @@ void process_timesync_req(void *taskparameter) {
 
     setMyTime(time_to_set, time_to_set_fraction_msec);
 
-    // end of time critical section: release I2C bus and re-enable app irq's
+  finish:
+    // end of time critical section: release I2C bus and app irq
+    I2C_MUTEX_UNLOCK();
     unmask_user_IRQ();
 
-  finish:
     timeSyncPending = false;
 
   } // infinite while(1)
diff --git a/src/wifiscan.cpp b/src/wifiscan.cpp
index 750f9c5a..85fdf6a1 100644
--- a/src/wifiscan.cpp
+++ b/src/wifiscan.cpp
@@ -57,8 +57,8 @@ void wifi_sniffer_init(void) {
   wificfg.nvs_enable = 0;        // we don't need any wifi settings from NVRAM
   wificfg.wifi_task_core_id = 0; // we want wifi task running on core 0
 
-  // wifi_promiscuous_filter_t filter = {
-  // .filter_mask = WIFI_PROMIS_FILTER_MASK_MGMT}; // only MGMT frames
+  //wifi_promiscuous_filter_t filter = {
+  //    .filter_mask = WIFI_PROMIS_FILTER_MASK_MGMT}; // only MGMT frames
   // .filter_mask = WIFI_PROMIS_FILTER_MASK_ALL}; // we use all frames
 
   wifi_promiscuous_filter_t filter = {.filter_mask =
@@ -73,7 +73,7 @@ void wifi_sniffer_init(void) {
   ESP_ERROR_CHECK(esp_wifi_set_mode(WIFI_MODE_NULL));
   ESP_ERROR_CHECK(esp_wifi_stop());
   ESP_ERROR_CHECK(
-      esp_wifi_set_promiscuous_filter(&filter)); // set MAC frame filter
+      esp_wifi_set_promiscuous_filter(&filter)); // set frame filter
   ESP_ERROR_CHECK(esp_wifi_set_promiscuous_rx_cb(&wifi_sniffer_packet_handler));
   ESP_ERROR_CHECK(esp_wifi_set_promiscuous(true)); // now switch on monitor mode