diff --git a/include/display.h b/include/display.h
index 0e94b806..8e503ce5 100644
--- a/include/display.h
+++ b/include/display.h
@@ -7,7 +7,8 @@
 extern uint8_t DisplayIsOn;
 
 void refreshTheDisplay(bool nextPage = false);
-void init_display(uint8_t verbose = 0);
+void init_display(bool verbose = false);
+void shutdown_display(void);
 void draw_page(time_t t, uint8_t page);
 void dp_printf(uint16_t x, uint16_t y, uint8_t font, uint8_t inv,
                const char *format, ...);
diff --git a/include/globals.h b/include/globals.h
index 76b733d4..9e41d441 100644
--- a/include/globals.h
+++ b/include/globals.h
@@ -51,6 +51,11 @@
 
 enum sendprio_t { prio_low, prio_normal, prio_high };
 enum timesource_t { _gps, _rtc, _lora, _unsynced };
+enum runmode_t {
+  RUNMODE_NORMAL,
+  RUNMODE_UPDATE,
+  RUNMODE_WAKEUP
+};
 
 // Struct holding devices's runtime configuration
 typedef struct {
diff --git a/include/i2cscan.h b/include/i2c.h
similarity index 80%
rename from include/i2cscan.h
rename to include/i2c.h
index 38487e76..ed042b31 100644
--- a/include/i2cscan.h
+++ b/include/i2c.h
@@ -1,5 +1,5 @@
-#ifndef _I2CSCAN_H
-#define _I2CSCAN_H
+#ifndef _I2C_H
+#define _I2C_H
 
 #include <Arduino.h>
 
@@ -11,6 +11,8 @@
 #define MCP_24AA02E64_PRIMARY_ADDRESS (0x50)
 #define QUECTEL_GPS_PRIMARY_ADDRESS (0x10)
 
+void i2c_init(void);
+void i2c_deinit(void);
 int i2c_scan(void);
 
 #endif
\ No newline at end of file
diff --git a/include/lorawan.h b/include/lorawan.h
index 4341b397..ead91d5c 100644
--- a/include/lorawan.h
+++ b/include/lorawan.h
@@ -21,6 +21,7 @@
 #endif
 
 extern TaskHandle_t lmicTask, lorasendTask;
+extern RTC_DATA_ATTR int RTCseqnoUp, RTCseqnoDn;
 
 // table of LORAWAN MAC commands
 typedef struct {
@@ -29,7 +30,7 @@ typedef struct {
   const uint8_t params;
 } mac_t;
 
-esp_err_t lora_stack_init();
+esp_err_t lora_stack_init(bool joined = false);
 void lora_setupForNetwork(bool preJoin);
 void lmictask(void *pvParameters);
 void gen_lora_deveui(uint8_t *pdeveui);
diff --git a/include/main.h b/include/main.h
index 4b5617cb..f57ce3f9 100644
--- a/include/main.h
+++ b/include/main.h
@@ -8,7 +8,7 @@
 
 #include "globals.h"
 #include "power.h"
-#include "i2cscan.h"
+#include "i2c.h"
 #include "blescan.h"
 #include "wifiscan.h"
 #include "configmanager.h"
@@ -18,6 +18,7 @@
 #include "irqhandler.h"
 #include "led.h"
 #include "spislave.h"
+
 #if (HAS_LORA)
 #include "lorawan.h"
 #endif
diff --git a/include/power.h b/include/power.h
index 1af87f09..8737e963 100644
--- a/include/power.h
+++ b/include/power.h
@@ -3,19 +3,24 @@
 
 #include <Arduino.h>
 #include <driver/adc.h>
+#include <driver/rtc_io.h>
 #include <esp_adc_cal.h>
-#include "i2cscan.h"
+#include "i2c.h"
 
 #define DEFAULT_VREF 1100 // tbd: use adc2_vref_to_gpio() for better estimate
 #define NO_OF_SAMPLES 64  // we do some multisampling to get better values
 
+extern RTC_DATA_ATTR runmode_t RTC_runmode;
+
 uint16_t read_voltage(void);
 void calibrate_voltage(void);
 bool batt_sufficient(void);
+void enter_deepsleep(const int wakeup_sec, const gpio_num_t wakeup_gpio);
+int exit_deepsleep(void);
 
 #ifdef HAS_PMU
 #include <axp20x.h>
-void power_event_IRQ(void);
+void AXP192_powerevent_IRQ(void);
 void AXP192_power(bool on);
 void AXP192_init(void);
 void AXP192_showstatus(void);
diff --git a/platformio.ini b/platformio.ini
index 1975fe69..80148ece 100644
--- a/platformio.ini
+++ b/platformio.ini
@@ -7,7 +7,7 @@
 
 ; ---> SELECT THE TARGET PLATFORM HERE! <---
 [board]
-halfile = generic.h
+;halfile = generic.h
 ;halfile = ebox.h
 ;halfile = eboxtube.h
 ;halfile = ecopower.h
@@ -19,7 +19,7 @@ halfile = generic.h
 ;halfile = ttgov21new.h
 ;halfile = ttgofox.h
 ;halfile = ttgobeam.h
-;halfile = ttgobeam10.h
+halfile = ttgobeam10.h
 ;halfile = fipy.h
 ;halfile = lopy.h
 ;halfile = lopy4.h
@@ -43,10 +43,10 @@ description = Paxcounter is a device for metering passenger flows in realtime. I
 
 [common]
 ; for release_version use max. 10 chars total, use any decimal format like "a.b.c"
-release_version = 1.9.6
+release_version = 1.9.63
 ; DEBUG LEVEL: For production run set to 0, otherwise device will leak RAM while running!
 ; 0=None, 1=Error, 2=Warn, 3=Info, 4=Debug, 5=Verbose
-debug_level = 3
+debug_level = 4
 extra_scripts = pre:build.py
 otakeyfile = ota.conf
 lorakeyfile = loraconf.h
diff --git a/src/configmanager.cpp b/src/configmanager.cpp
index 0fce294f..0fd6ca39 100644
--- a/src/configmanager.cpp
+++ b/src/configmanager.cpp
@@ -33,7 +33,6 @@ void defaultConfig() {
   cfg.vendorfilter = VENDORFILTER; // 0=disabled, 1=enabled
   cfg.rgblum = RGBLUMINOSITY;      // RGB Led luminosity (0..100%)
   cfg.monitormode = 0;             // 0=disabled, 1=enabled
-  cfg.runmode = 0;                 // 0=normal, 1=update
   cfg.payloadmask = PAYLOADMASK;   // all payload switched on
   cfg.bsecstate[BSEC_MAX_STATE_BLOB_SIZE] = {
       0}; // init BSEC state for BME680 sensor
@@ -157,10 +156,6 @@ void saveConfig() {
         flash8 != cfg.monitormode)
       nvs_set_i8(my_handle, "monitormode", cfg.monitormode);
 
-    if (nvs_get_i8(my_handle, "runmode", &flash8) != ESP_OK ||
-        flash8 != cfg.runmode)
-      nvs_set_i8(my_handle, "runmode", cfg.runmode);
-
     if (nvs_get_i16(my_handle, "rssilimit", &flash16) != ESP_OK ||
         flash16 != cfg.rssilimit)
       nvs_set_i16(my_handle, "rssilimit", cfg.rssilimit);
@@ -350,14 +345,6 @@ void loadConfig() {
       saveConfig();
     }
 
-    if (nvs_get_i8(my_handle, "runmode", &flash8) == ESP_OK) {
-      cfg.runmode = flash8;
-      ESP_LOGI(TAG, "Run mode = %d", flash8);
-    } else {
-      ESP_LOGI(TAG, "Run mode set to default %d", cfg.runmode);
-      saveConfig();
-    }
-
     nvs_close(my_handle);
     ESP_LOGI(TAG, "Done");
   }
diff --git a/src/cyclic.cpp b/src/cyclic.cpp
index 9b75ecef..86eae864 100644
--- a/src/cyclic.cpp
+++ b/src/cyclic.cpp
@@ -20,7 +20,7 @@ void doHousekeeping() {
   uptime();
 
   // check if update mode trigger switch was set
-  if (cfg.runmode == 1)
+  if (RTC_runmode == RUNMODE_UPDATE)
     do_reset();
 
   // task storage debugging //
diff --git a/src/display.cpp b/src/display.cpp
index 1e888f21..7f4da8f5 100644
--- a/src/display.cpp
+++ b/src/display.cpp
@@ -60,7 +60,7 @@ uint8_t displaybuf[DISPLAY_WIDTH * DISPLAY_HEIGHT / 8] = {0};
 
 QRCode qrcode;
 
-void init_display(uint8_t verbose) {
+void init_display(bool verbose) {
 
   // block i2c bus access
   if (!I2C_MUTEX_LOCK())
@@ -70,7 +70,7 @@ void init_display(uint8_t verbose) {
     // is we have display RST line we toggle it to re-initialize display
 #ifdef MY_OLED_RST
     pinMode(MY_OLED_RST, OUTPUT);
-    digitalWrite(MY_OLED_RST, 0); // iniialization of SSD1306 chip is executed
+    digitalWrite(MY_OLED_RST, 0); // initialization of SSD1306 chip is executed
     delay(1); // keep RES low for at least 3us according to SSD1306 datasheet
     digitalWrite(MY_OLED_RST, 1); // normal operation
 #endif
@@ -182,6 +182,18 @@ void refreshTheDisplay(bool nextPage) {
   } // mutex
 } // refreshDisplay()
 
+void shutdown_display(void) {
+  // block i2c bus access
+  if (!I2C_MUTEX_LOCK())
+    ESP_LOGV(TAG, "[%0.3f] i2c mutex lock failed", millis() / 1000.0);
+  else {
+    cfg.screenon = 0;
+    oledShutdown();
+    delay(DISPLAYREFRESH_MS / 1000 * 1.1);
+    I2C_MUTEX_UNLOCK(); // release i2c bus access
+  }
+}
+
 void draw_page(time_t t, uint8_t page) {
 
   char timeState;
diff --git a/src/i2cscan.cpp b/src/i2c.cpp
similarity index 78%
rename from src/i2cscan.cpp
rename to src/i2c.cpp
index d6e7ff64..4fe58adc 100644
--- a/src/i2cscan.cpp
+++ b/src/i2c.cpp
@@ -1,10 +1,30 @@
 // Basic config
 #include "globals.h"
-#include "i2cscan.h"
+#include "i2c.h"
 
 // Local logging tag
 static const char TAG[] = __FILE__;
 
+void i2c_init(void) {
+#ifdef HAS_DISPLAY
+  Wire.begin(MY_OLED_SDA, MY_OLED_SCL, 400000);
+#else
+  Wire.begin(SDA, SCL, 400000);
+#endif
+}
+
+void i2c_deinit(void) {
+  Wire.~TwoWire(); // shutdown/power off I2C hardware
+#ifdef HAS_DISPLAY
+  // to save power, because Wire.end() enables pullups
+  pinMode(MY_OLED_SDA, INPUT);
+  pinMode(MY_OLED_SCL, INPUT);
+#else
+  pinMode(SDA, INPUT);
+  pinMode(SCL, INPUT);
+#endif
+}
+
 int i2c_scan(void) {
 
   int i2c_ret, addr;
diff --git a/src/irqhandler.cpp b/src/irqhandler.cpp
index 8d1be880..63b85821 100644
--- a/src/irqhandler.cpp
+++ b/src/irqhandler.cpp
@@ -66,7 +66,7 @@ void irqHandler(void *pvParameters) {
 // do we have a power event?
 #if (HAS_PMU)
     if (InterruptStatus & PMU_IRQ)
-      power_event_IRQ();
+      AXP192_powerevent_IRQ();
 #endif
 
     // is time to send the payload?
diff --git a/src/lorawan.cpp b/src/lorawan.cpp
index 398e86f4..7e47ab0e 100644
--- a/src/lorawan.cpp
+++ b/src/lorawan.cpp
@@ -73,6 +73,10 @@ static const lmic_pinmap myPinmap = {
     .spi_freq = 8000000, // 8MHz
     .pConfig = &myHalConfig};
 
+RTC_DATA_ATTR u4_t RTCnetid, RTCdevaddr;
+RTC_DATA_ATTR u1_t RTCnwkKey[16], RTCartKey[16];
+RTC_DATA_ATTR int RTCseqnoUp, RTCseqnoDn;
+
 void lora_setupForNetwork(bool preJoin) {
 
   if (preJoin) {
@@ -86,9 +90,9 @@ void lora_setupForNetwork(bool preJoin) {
 #elif CFG_LMIC_EU_like
     // setting for TheThingsNetwork
     // TTN uses SF9, not SF12, for RX2 window
-    LMIC.dn2Dr = EU868_DR_SF9;
-    // Disable link check validation
-    LMIC_setLinkCheckMode(0);
+    // LMIC.dn2Dr = EU868_DR_SF9;
+    // Enable link check validation
+    LMIC_setLinkCheckMode(true);
 #endif
 
   } else {
@@ -103,6 +107,10 @@ void lora_setupForNetwork(bool preJoin) {
              getSfName(updr2rps(LMIC.datarate)),
              getBwName(updr2rps(LMIC.datarate)),
              getCrName(updr2rps(LMIC.datarate)));
+    // store keys and counters in RTC memory
+    LMIC_getSessionKeys(&RTCnetid, &RTCdevaddr, RTCnwkKey, RTCartKey);
+    RTCseqnoUp = LMIC.seqnoUp;
+    RTCseqnoDn = LMIC.seqnoDn;
   }
 }
 
@@ -244,9 +252,9 @@ void lora_send(void *pvParameters) {
   while (1) {
 
     // postpone until we are joined if we are not
-    // while (!LMIC.devaddr) {
-    //  vTaskDelay(pdMS_TO_TICKS(500));
-    //}
+    while (!LMIC.devaddr) {
+      vTaskDelay(pdMS_TO_TICKS(500));
+    }
 
     // fetch next or wait for payload to send from queue
     if (xQueueReceive(LoraSendQueue, &SendBuffer, portMAX_DELAY) != pdTRUE) {
@@ -287,7 +295,7 @@ void lora_send(void *pvParameters) {
   }
 }
 
-esp_err_t lora_stack_init() {
+esp_err_t lora_stack_init(bool joined) {
   assert(SEND_QUEUE_SIZE);
   LoraSendQueue = xQueueCreate(SEND_QUEUE_SIZE, sizeof(MessageBuffer_t));
   if (LoraSendQueue == 0) {
@@ -307,9 +315,17 @@ esp_err_t lora_stack_init() {
                           &lmicTask,  // task handle
                           1);         // CPU core
 
-  // start join
-  if (!LMIC_startJoining())
-    ESP_LOGI(TAG, "Already joined");
+  // start join if we did not wakeup from sleep, else continue session
+  if (!joined) {
+    if (!LMIC_startJoining())
+      ESP_LOGI(TAG, "Already joined");
+  } else {
+    LMIC_reset();
+    LMIC_setSession(RTCnetid, RTCdevaddr, RTCnwkKey, RTCartKey);
+    LMIC.seqnoUp = RTCseqnoUp;
+    LMIC.seqnoDn = RTCseqnoDn;
+    lora_setupForNetwork(true);
+    }
 
   // start lmic send task
   xTaskCreatePinnedToCore(lora_send,      // task function
diff --git a/src/main.cpp b/src/main.cpp
index f9bdce47..d366a762 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -131,51 +131,54 @@ void setup() {
 
   ESP_LOGI(TAG, "Starting Software v%s", PROGVERSION);
 
-  // print chip information on startup if in verbose mode
+  if (RTC_runmode == RUNMODE_WAKEUP)
+    exit_deepsleep();
+  else {
+
+    // print chip information on startup if in verbose mode
 #if (VERBOSE)
-  esp_chip_info_t chip_info;
-  esp_chip_info(&chip_info);
-  ESP_LOGI(TAG,
-           "This is ESP32 chip with %d CPU cores, WiFi%s%s, silicon revision "
-           "%d, %dMB %s Flash",
-           chip_info.cores, (chip_info.features & CHIP_FEATURE_BT) ? "/BT" : "",
-           (chip_info.features & CHIP_FEATURE_BLE) ? "/BLE" : "",
-           chip_info.revision, spi_flash_get_chip_size() / (1024 * 1024),
-           (chip_info.features & CHIP_FEATURE_EMB_FLASH) ? "embedded"
-                                                         : "external");
-  ESP_LOGI(TAG, "Internal Total heap %d, internal Free Heap %d",
-           ESP.getHeapSize(), ESP.getFreeHeap());
+    esp_chip_info_t chip_info;
+    esp_chip_info(&chip_info);
+    ESP_LOGI(TAG,
+             "This is ESP32 chip with %d CPU cores, WiFi%s%s, silicon revision "
+             "%d, %dMB %s Flash",
+             chip_info.cores,
+             (chip_info.features & CHIP_FEATURE_BT) ? "/BT" : "",
+             (chip_info.features & CHIP_FEATURE_BLE) ? "/BLE" : "",
+             chip_info.revision, spi_flash_get_chip_size() / (1024 * 1024),
+             (chip_info.features & CHIP_FEATURE_EMB_FLASH) ? "embedded"
+                                                           : "external");
+    ESP_LOGI(TAG, "Internal Total heap %d, internal Free Heap %d",
+             ESP.getHeapSize(), ESP.getFreeHeap());
 #ifdef BOARD_HAS_PSRAM
-  ESP_LOGI(TAG, "SPIRam Total heap %d, SPIRam Free Heap %d", ESP.getPsramSize(),
-           ESP.getFreePsram());
+    ESP_LOGI(TAG, "SPIRam Total heap %d, SPIRam Free Heap %d",
+             ESP.getPsramSize(), ESP.getFreePsram());
 #endif
-  ESP_LOGI(TAG, "ChipRevision %d, Cpu Freq %d, SDK Version %s",
-           ESP.getChipRevision(), ESP.getCpuFreqMHz(), ESP.getSdkVersion());
-  ESP_LOGI(TAG, "Flash Size %d, Flash Speed %d", ESP.getFlashChipSize(),
-           ESP.getFlashChipSpeed());
-  ESP_LOGI(TAG, "Wifi/BT software coexist version %s", esp_coex_version_get());
+    ESP_LOGI(TAG, "ChipRevision %d, Cpu Freq %d, SDK Version %s",
+             ESP.getChipRevision(), ESP.getCpuFreqMHz(), ESP.getSdkVersion());
+    ESP_LOGI(TAG, "Flash Size %d, Flash Speed %d", ESP.getFlashChipSize(),
+             ESP.getFlashChipSpeed());
+    ESP_LOGI(TAG, "Wifi/BT software coexist version %s",
+             esp_coex_version_get());
 
 #if (HAS_LORA)
-  ESP_LOGI(TAG, "IBM LMIC version %d.%d.%d", LMIC_VERSION_MAJOR,
-           LMIC_VERSION_MINOR, LMIC_VERSION_BUILD);
-  ESP_LOGI(TAG, "Arduino LMIC version %d.%d.%d.%d",
-           ARDUINO_LMIC_VERSION_GET_MAJOR(ARDUINO_LMIC_VERSION),
-           ARDUINO_LMIC_VERSION_GET_MINOR(ARDUINO_LMIC_VERSION),
-           ARDUINO_LMIC_VERSION_GET_PATCH(ARDUINO_LMIC_VERSION),
-           ARDUINO_LMIC_VERSION_GET_LOCAL(ARDUINO_LMIC_VERSION));
-  showLoraKeys();
+    ESP_LOGI(TAG, "IBM LMIC version %d.%d.%d", LMIC_VERSION_MAJOR,
+             LMIC_VERSION_MINOR, LMIC_VERSION_BUILD);
+    ESP_LOGI(TAG, "Arduino LMIC version %d.%d.%d.%d",
+             ARDUINO_LMIC_VERSION_GET_MAJOR(ARDUINO_LMIC_VERSION),
+             ARDUINO_LMIC_VERSION_GET_MINOR(ARDUINO_LMIC_VERSION),
+             ARDUINO_LMIC_VERSION_GET_PATCH(ARDUINO_LMIC_VERSION),
+             ARDUINO_LMIC_VERSION_GET_LOCAL(ARDUINO_LMIC_VERSION));
+    showLoraKeys();
 #endif // HAS_LORA
 
 #if (HAS_GPS)
-  ESP_LOGI(TAG, "TinyGPS+ version %s", TinyGPSPlus::libraryVersion());
+    ESP_LOGI(TAG, "TinyGPS+ version %s", TinyGPSPlus::libraryVersion());
 #endif
+  }
 
-// open i2c bus
-#ifdef HAS_DISPLAY
-  Wire.begin(MY_OLED_SDA, MY_OLED_SCL, 400000);
-#else
-  Wire.begin(SDA, SCL, 400000);
-#endif
+  // open i2c bus
+  i2c_init();
 
 // setup power on boards with power management logic
 #ifdef EXT_POWER_SW
@@ -197,7 +200,7 @@ void setup() {
 #ifdef HAS_DISPLAY
   strcat_P(features, " OLED");
   DisplayIsOn = cfg.screenon;
-  init_display(!cfg.runmode); // note: blocking call
+  init_display(RTC_runmode == RUNMODE_NORMAL); // note: blocking call
 #endif
 
   // scan i2c bus for devices
@@ -266,9 +269,8 @@ void setup() {
 #if (USE_OTA)
   strcat_P(features, " OTA");
   // reboot to firmware update mode if ota trigger switch is set
-  if (cfg.runmode == 1) {
-    cfg.runmode = 0;
-    saveConfig();
+  if (RTC_runmode == RUNMODE_UPDATE) {
+    RTC_runmode = RUNMODE_NORMAL;
     start_ota_update();
   }
 #endif
@@ -283,11 +285,11 @@ void setup() {
   } else
     btStop();
 #else
-  // 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_WIFI)); // configure Wifi/BT coexist lib
+    // 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_WIFI)); // configure Wifi/BT coexist lib
 #endif
 
 // initialize gps
@@ -314,7 +316,7 @@ void setup() {
 // initialize LoRa
 #if (HAS_LORA)
   strcat_P(features, " LORA");
-  assert(lora_stack_init() == ESP_OK);
+  assert(lora_stack_init(RTC_runmode == RUNMODE_WAKEUP) == ESP_OK);
 #endif
 
 // initialize SPI
@@ -338,11 +340,11 @@ void setup() {
 #if PAYLOAD_ENCODER == 1
   strcat_P(features, " PLAIN");
 #elif PAYLOAD_ENCODER == 2
-  strcat_P(features, " PACKED");
+    strcat_P(features, " PACKED");
 #elif PAYLOAD_ENCODER == 3
-  strcat_P(features, " LPPDYN");
+    strcat_P(features, " LPPDYN");
 #elif PAYLOAD_ENCODER == 4
-  strcat_P(features, " LPPPKD");
+    strcat_P(features, " LPPPKD");
 #endif
 
   // initialize RTC
@@ -369,10 +371,10 @@ void setup() {
   // function gets it's seed from RF noise
   get_salt(); // get new 16bit for salting hashes
 #else
-  // switch off wifi
-  WiFi.mode(WIFI_OFF);
-  esp_wifi_stop();
-  esp_wifi_deinit();
+    // switch off wifi
+    WiFi.mode(WIFI_OFF);
+    esp_wifi_stop();
+    esp_wifi_deinit();
 #endif
 
   // start state machine
@@ -465,6 +467,9 @@ void setup() {
   // show compiled features
   ESP_LOGI(TAG, "Features:%s", features);
 
+  // set runmode to normal
+  RTC_runmode = RUNMODE_NORMAL;
+
   vTaskDelete(NULL);
 
 } // setup()
diff --git a/src/power.cpp b/src/power.cpp
index 597f68e8..73b3991f 100644
--- a/src/power.cpp
+++ b/src/power.cpp
@@ -5,11 +5,14 @@
 // Local logging tag
 static const char TAG[] = __FILE__;
 
+RTC_DATA_ATTR struct timeval sleep_enter_time;
+RTC_DATA_ATTR runmode_t RTC_runmode = RUNMODE_NORMAL;
+
 #ifdef HAS_PMU
 
 AXP20X_Class pmu;
 
-void power_event_IRQ(void) {
+void AXP192_powerevent_IRQ(void) {
 
   pmu.readIRQ();
 
@@ -34,10 +37,12 @@ void power_event_IRQ(void) {
   if (pmu.isBattTempHighIRQ())
     ESP_LOGI(TAG, "Battery low temperature.");
 
-  // display on/off
-  // if (pmu.isPEKShortPressIRQ()) {
-  //  cfg.screenon = !cfg.screenon;
-  //}
+// esp32 sleep mode, can be exited by pressing user button
+#ifdef HAS_BUTTON
+  if (pmu.isPEKShortPressIRQ() && (RTC_runmode == RUNMODE_NORMAL)) {
+    enter_deepsleep(0, HAS_BUTTON);
+  }
+#endif
 
   // shutdown power
   if (pmu.isPEKLongtPressIRQ()) {
@@ -60,7 +65,8 @@ void AXP192_power(bool on) {
     pmu.setChgLEDMode(AXP20X_LED_BLINK_1HZ);
   } else {
     pmu.setChgLEDMode(AXP20X_LED_OFF);
-    pmu.setPowerOutPut(AXP192_DCDC1, AXP202_OFF);
+    // we don't cut off power of display, because then display blocks i2c bus
+    // pmu.setPowerOutPut(AXP192_DCDC1, AXP202_OFF);
     pmu.setPowerOutPut(AXP192_LDO3, AXP202_OFF);
     pmu.setPowerOutPut(AXP192_LDO2, AXP202_OFF);
   }
@@ -185,6 +191,85 @@ static const adc_unit_t unit = ADC_UNIT_1;
 
 #endif // BAT_MEASURE_ADC
 
+void enter_deepsleep(const int wakeup_sec, const gpio_num_t wakeup_gpio) {
+
+  if ((!wakeup_sec) && (!wakeup_gpio) && (RTC_runmode == RUNMODE_NORMAL))
+    return;
+
+  // set wakeup timer
+  if (wakeup_sec)
+    esp_sleep_enable_timer_wakeup(wakeup_sec * 1000000);
+
+  // set wakeup gpio
+  if (wakeup_gpio != NOT_A_PIN) {
+    rtc_gpio_isolate(wakeup_gpio);
+    esp_sleep_enable_ext1_wakeup(1ULL << wakeup_gpio, ESP_EXT1_WAKEUP_ALL_LOW);
+  }
+
+  // store LMIC counters and time
+  RTCseqnoUp = LMIC.seqnoUp;
+  RTCseqnoDn = LMIC.seqnoDn;
+
+  // store sleep enter time
+  gettimeofday(&sleep_enter_time, NULL);
+
+  // halt interrupts accessing i2c bus
+  mask_user_IRQ();
+
+// switch off display
+#ifdef HAS_DISPLAY
+  shutdown_display();
+#endif
+
+// switch off wifi & ble
+#if (BLECOUNTER)
+  stop_BLEscan();
+#endif
+
+// switch off power if has PMU
+#ifdef HAS_PMU
+  AXP192_power(false); // switch off Lora, GPS, display
+#endif
+
+  // shutdown i2c bus
+  i2c_deinit();
+
+  // enter sleep mode
+  esp_deep_sleep_start();
+}
+
+int exit_deepsleep(void) {
+
+  struct timeval now;
+  gettimeofday(&now, NULL);
+  int sleep_time_ms = (now.tv_sec - sleep_enter_time.tv_sec) * 1000 +
+                      (now.tv_usec - sleep_enter_time.tv_usec) / 1000;
+
+  // switch on power if has PMU
+#ifdef HAS_PMU
+  AXP192_power(true); // power on Lora, GPS, display
+#endif
+
+  // re-init i2c bus
+  void i2c_init();
+
+  switch (esp_sleep_get_wakeup_cause()) {
+  case ESP_SLEEP_WAKEUP_EXT1:
+  case ESP_SLEEP_WAKEUP_TIMER:
+    RTC_runmode = RUNMODE_WAKEUP;
+    ESP_LOGI(TAG, "[%0.3f] wake up from deep sleep after %dms", sleep_time_ms);
+    break;
+  case ESP_SLEEP_WAKEUP_UNDEFINED:
+  default:
+    RTC_runmode = RUNMODE_NORMAL;
+  }
+
+  if (RTC_runmode == RUNMODE_WAKEUP)
+    return sleep_time_ms;
+  else
+    return -1;
+}
+
 void calibrate_voltage(void) {
 #ifdef BAT_MEASURE_ADC
 // configure ADC
diff --git a/src/rcommand.cpp b/src/rcommand.cpp
index 4290555c..24972c73 100644
--- a/src/rcommand.cpp
+++ b/src/rcommand.cpp
@@ -37,7 +37,7 @@ void set_reset(uint8_t val[]) {
   case 9: // reset and ask for software update via Wifi OTA
     ESP_LOGI(TAG, "Remote command: software update via Wifi");
 #if (USE_OTA)
-    cfg.runmode = 1;
+    RTC_runmode = RUNMODE_UPDATE;
 #endif // USE_OTA
     break;