diff --git a/include/i2c.h b/include/i2c.h
index dcf3c8ef..7fcbd33a 100644
--- a/include/i2c.h
+++ b/include/i2c.h
@@ -24,7 +24,7 @@
 void i2c_init(void);
 void i2c_deinit(void);
 void i2c_scan(void);
-uint8_t i2c_readBytes(uint8_t addr, uint8_t reg, uint8_t *data, uint8_t len);
-uint8_t i2c_writeBytes(uint8_t addr, uint8_t reg, uint8_t *data, uint8_t len);
+int i2c_readBytes(uint8_t addr, uint8_t reg, uint8_t *data, uint8_t len);
+int i2c_writeBytes(uint8_t addr, uint8_t reg, uint8_t *data, uint8_t len);
 
 #endif
\ No newline at end of file
diff --git a/platformio_orig.ini b/platformio_orig.ini
index 26c79e8a..4d9163a3 100644
--- a/platformio_orig.ini
+++ b/platformio_orig.ini
@@ -48,7 +48,7 @@ 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 = 2.2.0
+release_version = 2.3.0
 ; 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
@@ -56,7 +56,7 @@ extra_scripts = pre:build.py
 otakeyfile = ota.conf
 lorakeyfile = loraconf.h
 lmicconfigfile = lmic_config.h
-platform_espressif32 = espressif32@2.1.0
+platform_espressif32 = espressif32@3.0.0
 monitor_speed = 115200
 upload_speed = 115200 ; set by build.py and taken from hal file
 display_library = ; set by build.py and taken from hal file
@@ -85,7 +85,8 @@ lib_deps_basic =
     jchristensen/Timezone @ ^1.2.4
     makuna/RTC @ ^2.3.5
     spacehuhn/SimpleButton 
-    lewisxhe/AXP202X_Library @ ^1.1.2
+    ;lewisxhe/AXP202X_Library @ ^1.1.2
+    https://github.com/lewisxhe/AXP202X_Library.git
     geeksville/esp32-micro-sdcard @ ^0.1.1
     256dpi/MQTT @ ^2.4.7
 lib_deps_all =
diff --git a/src/gpsread.cpp b/src/gpsread.cpp
index a38a175d..d253bcb2 100644
--- a/src/gpsread.cpp
+++ b/src/gpsread.cpp
@@ -119,7 +119,7 @@ time_t get_gpstime(uint16_t *msec) {
     tm.Year = CalendarYrToTm(atoi(gpsyear.value())); // year offset from 1970
     t = makeTime(tm);
 
-    ESP_LOGD(TAG, "GPS time/date = %2d:%2d:%2d / %2d.%2d.%2d", tm.Hour,
+    ESP_LOGD(TAG, "GPS time/date = %02d:%02d:%02d / %02d.%02d.%2d", tm.Hour,
             tm.Minute, tm.Second, tm.Day, tm.Month, tm.Year + 1970);
 
     // add protocol delay with millisecond precision
diff --git a/src/i2c.cpp b/src/i2c.cpp
index 226d08c8..f8f1bbdf 100644
--- a/src/i2c.cpp
+++ b/src/i2c.cpp
@@ -84,7 +84,7 @@ void i2c_scan(void) {
 }
 
 // mutexed functions for i2c r/w access
-uint8_t i2c_readBytes(uint8_t addr, uint8_t reg, uint8_t *data, uint8_t len) {
+int i2c_readBytes(uint8_t addr, uint8_t reg, uint8_t *data, uint8_t len) {
   if (I2C_MUTEX_LOCK()) {
 
     uint8_t ret = 0;
@@ -112,7 +112,7 @@ uint8_t i2c_readBytes(uint8_t addr, uint8_t reg, uint8_t *data, uint8_t len) {
   }
 }
 
-uint8_t i2c_writeBytes(uint8_t addr, uint8_t reg, uint8_t *data, uint8_t len) {
+int i2c_writeBytes(uint8_t addr, uint8_t reg, uint8_t *data, uint8_t len) {
   if (I2C_MUTEX_LOCK()) {
 
     uint8_t ret = 0;
diff --git a/src/power.cpp b/src/power.cpp
index 70c300dd..048a4385 100644
--- a/src/power.cpp
+++ b/src/power.cpp
@@ -46,6 +46,14 @@ void AXP192_powerevent_IRQ(void) {
     ESP_LOGI(TAG, "Battery high temperature.");
   if (pmu.isBattTempHighIRQ())
     ESP_LOGI(TAG, "Battery low temperature.");
+  if (pmu.isLowVoltageLevel1IRQ()) {
+    ESP_LOGI(TAG, "Battery has reached voltage level 1.");
+    pmu.setChgLEDMode(AXP20X_LED_BLINK_4HZ);
+  }
+  if (pmu.isLowVoltageLevel2IRQ()) {
+    ESP_LOGI(TAG, "Battery has reached voltage level 2.");
+    pmu.setChgLEDMode(AXP20X_LED_BLINK_1HZ);
+  }
 
   // short press -> esp32 deep sleep mode, can be exited by pressing user button
   if (pmu.isPEKShortPressIRQ()) {
@@ -129,10 +137,15 @@ void AXP192_init(void) {
     pmu.setLDO2Voltage(3300);  // LORA VDD 3v3
     pmu.setLDO3Voltage(3300);  // GPS VDD 3v3
 
+    // configure voltage warning levels
+    pmu.setVWarningLevel1(3600);
+    pmu.setVWarningLevel2(3800);
+    pmu.setPowerDownVoltage(3300);
+
     // configure PEK button settings
     pmu.setTimeOutShutdown(false); // forced shutdown by PEK enabled
     pmu.setShutdownTime(
-        AXP_POWER_OFF_TIME_65); // 6 sec button press for shutdown
+        AXP_POWER_OFF_TIME_6S); // 6 sec button press for shutdown
     pmu.setlongPressTime(
         AXP_LONGPRESS_TIME_1S5); // 1.5 sec button press for long press
     pmu.setStartupTime(
diff --git a/src/rcommand.cpp b/src/rcommand.cpp
index d39ba1f3..c902a9d5 100644
--- a/src/rcommand.cpp
+++ b/src/rcommand.cpp
@@ -166,7 +166,7 @@ void set_payloadmask(uint8_t val[]) {
 
 void set_sensor(uint8_t val[]) {
 #if (HAS_SENSORS)
-  switch (val[0]) { // check if valid sensor number 1...4
+  switch (val[0]) { // check if valid sensor number 1..3
   case 1:
   case 2:
   case 3: