diff --git a/cmake-nRF5x/CMake_nRF5x.cmake b/cmake-nRF5x/CMake_nRF5x.cmake
index ead7b9f6..c7d0a68b 100755
--- a/cmake-nRF5x/CMake_nRF5x.cmake
+++ b/cmake-nRF5x/CMake_nRF5x.cmake
@@ -74,21 +74,6 @@ macro(nRF5x_setup)
                 )
     endif ()
 
-    set(COMMON_FLAGS "-MP -MD -mthumb -mabi=aapcs -Wall -g3 -ffunction-sections -fdata-sections -fno-strict-aliasing -fno-builtin --short-enums ${CPU_FLAGS} -Wreturn-type -Werror=return-type")
-
-    # compiler/assambler/linker flags
-    set(CMAKE_C_FLAGS "${COMMON_FLAGS}")
-    set(CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} -O0 -g3")
-    set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -O3")
-    set(CMAKE_CXX_FLAGS "${COMMON_FLAGS}")
-    set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -O0 -g3")
-    set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -O3")
-    set(CMAKE_ASM_FLAGS "-MP -MD -x assembler-with-cpp")
-    set(CMAKE_EXE_LINKER_FLAGS "-mthumb -mabi=aapcs -L ${NRF5_SDK_PATH}/modules/nrfx/mdk -T${NRF5_LINKER_SCRIPT} ${CPU_FLAGS} -Wl,--gc-sections --specs=nano.specs -lc -lnosys -lm")
-    # note: we must override the default cmake linker flags so that CMAKE_C_FLAGS are not added implicitly
-    set(CMAKE_C_LINK_EXECUTABLE "${CMAKE_C_COMPILER} <LINK_FLAGS> <OBJECTS> -o <TARGET> <LINK_LIBRARIES>")
-    set(CMAKE_CXX_LINK_EXECUTABLE "${CMAKE_C_COMPILER} <LINK_FLAGS> <OBJECTS> -lstdc++ -o <TARGET> <LINK_LIBRARIES>")
-
     # basic board definitions and drivers
     include_directories(
             "${NRF5_SDK_PATH}/components"
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 43608568..cd729921 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -744,7 +744,7 @@ link_directories(
 )
 
 
-set(COMMON_FLAGS -MP -MD -mthumb -mabi=aapcs -Wall -Wno-unknown-pragmas -g3 -ffunction-sections -fdata-sections -fno-strict-aliasing -fno-builtin --short-enums -mcpu=cortex-m4 -mfloat-abi=hard -mfpu=fpv4-sp-d16 -Wreturn-type -Werror=return-type)
+set(COMMON_FLAGS -MP -MD -mthumb -mabi=aapcs -Wall -Wno-unknown-pragmas -g3 -ffunction-sections -fdata-sections -fno-strict-aliasing -fno-builtin --short-enums -mcpu=cortex-m4 -mfloat-abi=hard -mfpu=fpv4-sp-d16 -Wreturn-type -Werror=return-type -fstack-usage -fno-exceptions -fno-non-call-exceptions)
 add_definitions(-DCONFIG_GPIO_AS_PINRESET)
 add_definitions(-DNIMBLE_CFG_CONTROLLER)
 add_definitions(-DOS_CPUTIME_FREQ)
@@ -766,10 +766,10 @@ add_library(nrf-sdk STATIC ${SDK_SOURCE_FILES})
 target_include_directories(nrf-sdk SYSTEM PUBLIC . ../)
 target_include_directories(nrf-sdk SYSTEM PUBLIC ${INCLUDES_FROM_LIBS})
 target_compile_options(nrf-sdk PRIVATE
-        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -O0 -g3>
-        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -O3>
-        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -O0>
-        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -O3>
+        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -Og -g3>
+        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -Os>
+        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -Og -fno-rtti>
+        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -Os -fno-rtti>
         $<$<COMPILE_LANGUAGE:ASM>: -MP -MD -x assembler-with-cpp>
         )
 
@@ -778,10 +778,10 @@ add_library(nimble STATIC ${NIMBLE_SRC} ${TINYCRYPT_SRC})
 target_include_directories(nimble SYSTEM PUBLIC . ../)
 target_include_directories(nimble SYSTEM PUBLIC ${INCLUDES_FROM_LIBS})
 target_compile_options(nimble PRIVATE
-        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -O0 -g3 -Wno-unused-but-set-variable -Wno-maybe-uninitialized>
-        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -O3 -Wno-unused-but-set-variable -Wno-maybe-uninitialized>
-        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -O0 -g3 -Wno-unused-but-set-variable -Wno-maybe-uninitialized>
-        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -O3 -Wno-unused-but-set-variable -Wno-maybe-uninitialized>
+        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -Og -g3 -Wno-unused-but-set-variable -Wno-maybe-uninitialized>
+        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -Os -Wno-unused-but-set-variable -Wno-maybe-uninitialized>
+        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -Og -g3 -Wno-unused-but-set-variable -Wno-maybe-uninitialized -fno-rtti>
+        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -Os -Wno-unused-but-set-variable -Wno-maybe-uninitialized -fno-rtti>
         $<$<COMPILE_LANGUAGE:ASM>: -MP -MD -x assembler-with-cpp>
         )
 
@@ -790,10 +790,10 @@ add_library(lvgl STATIC ${LVGL_SRC})
 target_include_directories(lvgl SYSTEM PUBLIC . ../)
 target_include_directories(lvgl SYSTEM PUBLIC ${INCLUDES_FROM_LIBS})
 target_compile_options(lvgl PRIVATE
-        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -O0 -g3>
-        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -O3>
-        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -O0 -g3>
-        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -O3>
+        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -Og -g3>
+        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -Os>
+        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -Og -g3 -fno-rtti>
+        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -Os -fno-rtti>
         $<$<COMPILE_LANGUAGE:ASM>: -MP -MD -x assembler-with-cpp>
         )
 
@@ -805,10 +805,10 @@ add_executable(${EXECUTABLE_NAME} ${SOURCE_FILES})
 set_target_properties(${EXECUTABLE_NAME} PROPERTIES OUTPUT_NAME ${EXECUTABLE_FILE_NAME})
 target_link_libraries(${EXECUTABLE_NAME} nimble nrf-sdk lvgl)
 target_compile_options(${EXECUTABLE_NAME} PUBLIC
-        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -O0 -g3>
-        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -O3>
-        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -O0 -g3>
-        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -O3>
+        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -Og -g3>
+        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -Os>
+        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -Og -g3 -fno-rtti>
+        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -Os -fno-rtti>
         $<$<COMPILE_LANGUAGE:ASM>: -MP -MD -x assembler-with-cpp>
         )
 
@@ -835,10 +835,10 @@ add_executable(${EXECUTABLE_MCUBOOT_NAME} ${SOURCE_FILES})
 target_link_libraries(${EXECUTABLE_MCUBOOT_NAME} nimble nrf-sdk lvgl)
 set_target_properties(${EXECUTABLE_MCUBOOT_NAME} PROPERTIES OUTPUT_NAME ${EXECUTABLE_MCUBOOT_FILE_NAME})
 target_compile_options(${EXECUTABLE_MCUBOOT_NAME} PUBLIC
-        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -O0 -g3>
-        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -O3>
-        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -O0 -g3>
-        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -O3>
+        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -Og -g3>
+        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -Os>
+        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -Og -g3 -fno-rtti>
+        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -Os -fno-rtti>
         $<$<COMPILE_LANGUAGE:ASM>: -MP -MD -x assembler-with-cpp>
         )
 
@@ -872,10 +872,10 @@ target_link_libraries(${EXECUTABLE_RECOVERY_NAME} nimble nrf-sdk)
 set_target_properties(${EXECUTABLE_RECOVERY_NAME} PROPERTIES OUTPUT_NAME ${EXECUTABLE_RECOVERY_FILE_NAME})
 target_compile_definitions(${EXECUTABLE_RECOVERY_NAME} PUBLIC "PINETIME_IS_RECOVERY")
 target_compile_options(${EXECUTABLE_RECOVERY_NAME} PUBLIC
-        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -O0 -g3>
-        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -O3>
-        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -O0 -g3>
-        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -O3>
+        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -Og -g3>
+        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -Os>
+        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -Og -g3 -fno-rtti>
+        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -Os -fno-rtti>
         $<$<COMPILE_LANGUAGE:ASM>: -MP -MD -x assembler-with-cpp>
         )
 
@@ -902,10 +902,10 @@ target_link_libraries(${EXECUTABLE_RECOVERY_MCUBOOT_NAME} nimble nrf-sdk)
 set_target_properties(${EXECUTABLE_RECOVERY_MCUBOOT_NAME} PROPERTIES OUTPUT_NAME ${EXECUTABLE_RECOVERY_MCUBOOT_FILE_NAME})
 target_compile_definitions(${EXECUTABLE_RECOVERY_MCUBOOT_NAME} PUBLIC "PINETIME_IS_RECOVERY")
 target_compile_options(${EXECUTABLE_RECOVERY_MCUBOOT_NAME} PUBLIC
-        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -O0 -g3>
-        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -O3>
-        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -O0 -g3>
-        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -O3>
+        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -Og -g3>
+        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -Os>
+        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -Og -g3 -fno-rtti>
+        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -Os -fno-rtti>
         $<$<COMPILE_LANGUAGE:ASM>: -MP -MD -x assembler-with-cpp>
         )
 
@@ -939,10 +939,10 @@ add_executable(${EXECUTABLE_RECOVERYLOADER_NAME} ${RECOVERYLOADER_SOURCE_FILES})
 target_link_libraries(${EXECUTABLE_RECOVERYLOADER_NAME} nrf-sdk)
 set_target_properties(${EXECUTABLE_RECOVERYLOADER_NAME} PROPERTIES OUTPUT_NAME ${EXECUTABLE_RECOVERYLOADER_FILE_NAME})
 target_compile_options(${EXECUTABLE_RECOVERYLOADER_NAME} PUBLIC
-        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -O0 -g3>
-        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -O3>
-        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -O0 -g3>
-        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -O3>
+        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -Og -g3>
+        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -Os>
+        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -Og -g3 -fno-rtti>
+        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -Os -fno-rtti>
         $<$<COMPILE_LANGUAGE:ASM>: -MP -MD -x assembler-with-cpp>
         )
 target_include_directories(${EXECUTABLE_RECOVERYLOADER_NAME} PUBLIC
@@ -972,10 +972,10 @@ add_executable(${EXECUTABLE_MCUBOOT_RECOVERYLOADER_NAME} ${RECOVERYLOADER_SOURCE
 target_link_libraries(${EXECUTABLE_MCUBOOT_RECOVERYLOADER_NAME} nrf-sdk)
 set_target_properties(${EXECUTABLE_MCUBOOT_RECOVERYLOADER_NAME} PROPERTIES OUTPUT_NAME ${EXECUTABLE_MCUBOOT_RECOVERYLOADER_FILE_NAME})
 target_compile_options(${EXECUTABLE_MCUBOOT_RECOVERYLOADER_NAME} PUBLIC
-        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -O0 -g3>
-        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -O3>
-        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -O0 -g3>
-        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -O3>
+        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -Og -g3>
+        $<$<AND:$<COMPILE_LANGUAGE:C>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -Os>
+        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:DEBUG>>: ${COMMON_FLAGS} -Og -g3 -fno-rtti>
+        $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CONFIG:RELEASE>>: ${COMMON_FLAGS} -Os -fno-rtti>
         $<$<COMPILE_LANGUAGE:ASM>: -MP -MD -x assembler-with-cpp>
         )
 target_include_directories(${EXECUTABLE_MCUBOOT_RECOVERYLOADER_NAME} PUBLIC
diff --git a/src/displayapp/DisplayApp.cpp b/src/displayapp/DisplayApp.cpp
index 419b9f6f..7b03d569 100644
--- a/src/displayapp/DisplayApp.cpp
+++ b/src/displayapp/DisplayApp.cpp
@@ -153,7 +153,7 @@ void DisplayApp::Refresh() {
         break;
       case Messages::TimerDone:
         if (currentApp == Apps::Timer) {
-          auto *timer = dynamic_cast<Screens::Timer*>(currentScreen.get());
+          auto *timer = static_cast<Screens::Timer*>(currentScreen.get());
           timer->setDone();
         } else {
           LoadApp(Apps::Timer, DisplayApp::FullRefreshDirections::Down);