diff --git a/bsp/stm32/stm32f103-blue-pill/rtconfig.py b/bsp/stm32/stm32f103-blue-pill/rtconfig.py
index a6d89ffdfd..43e61097a2 100644
--- a/bsp/stm32/stm32f103-blue-pill/rtconfig.py
+++ b/bsp/stm32/stm32f103-blue-pill/rtconfig.py
@@ -52,7 +52,7 @@ if PLATFORM == 'gcc':
     LPATH = ''
 
     if BUILD == 'debug':
-        CFLAGS += ' -O0 -gdwarf-2 -g'
+        CFLAGS += ' -O2 -gdwarf-2 -g'
         AFLAGS += ' -gdwarf-2'
     else:
         CFLAGS += ' -O2'
@@ -83,7 +83,7 @@ elif PLATFORM == 'armcc':
     EXEC_PATH += '/ARM/ARMCC/bin/'
 
     if BUILD == 'debug':
-        CFLAGS += ' -g -O0'
+        CFLAGS += ' -g -O2'
         AFLAGS += ' -g'
     else:
         CFLAGS += ' -O2'
@@ -165,7 +165,7 @@ elif PLATFORM == 'iar':
 
     if BUILD == 'debug':
         CFLAGS += ' --debug'
-        CFLAGS += ' -On'
+        CFLAGS += ' -Oh'
     else:
         CFLAGS += ' -Oh'
 
diff --git a/bsp/stm32/stm32f302-st-nucleo/rtconfig.py b/bsp/stm32/stm32f302-st-nucleo/rtconfig.py
index 871c33548c..c1d6bcf869 100644
--- a/bsp/stm32/stm32f302-st-nucleo/rtconfig.py
+++ b/bsp/stm32/stm32f302-st-nucleo/rtconfig.py
@@ -52,7 +52,7 @@ if PLATFORM == 'gcc':
     LPATH = ''
 
     if BUILD == 'debug':
-        CFLAGS += ' -O0 -gdwarf-2 -g'
+        CFLAGS += ' -O2 -gdwarf-2 -g'
         AFLAGS += ' -gdwarf-2'
     else:
         CFLAGS += ' -O2'
@@ -83,7 +83,7 @@ elif PLATFORM == 'armcc':
     EXEC_PATH += '/ARM/ARMCC/bin/'
 
     if BUILD == 'debug':
-        CFLAGS += ' -g -O0'
+        CFLAGS += ' -g -O2'
         AFLAGS += ' -g'
     else:
         CFLAGS += ' -O2'
@@ -164,7 +164,7 @@ elif PLATFORM == 'iar':
 
     if BUILD == 'debug':
         CFLAGS += ' --debug'
-        CFLAGS += ' -On'
+        CFLAGS += ' -Oh'
     else:
         CFLAGS += ' -Oh'
 
diff --git a/bsp/stm32/stm32l010-st-nucleo/rtconfig.py b/bsp/stm32/stm32l010-st-nucleo/rtconfig.py
index 79558e8877..8eeff0e7be 100644
--- a/bsp/stm32/stm32l010-st-nucleo/rtconfig.py
+++ b/bsp/stm32/stm32l010-st-nucleo/rtconfig.py
@@ -52,7 +52,7 @@ if PLATFORM == 'gcc':
     LPATH = ''
 
     if BUILD == 'debug':
-        CFLAGS += ' -O0 -gdwarf-2 -g'
+        CFLAGS += ' -O2 -gdwarf-2 -g'
         AFLAGS += ' -gdwarf-2'
     else:
         CFLAGS += ' -O2'
@@ -83,7 +83,7 @@ elif PLATFORM == 'armcc':
     EXEC_PATH += '/ARM/ARMCC/bin/'
 
     if BUILD == 'debug':
-        CFLAGS += ' -g -O0'
+        CFLAGS += ' -g -O2'
         AFLAGS += ' -g'
     else:
         CFLAGS += ' -O2'
@@ -164,7 +164,7 @@ elif PLATFORM == 'iar':
 
     if BUILD == 'debug':
         CFLAGS += ' --debug'
-        CFLAGS += ' -On'
+        CFLAGS += ' -Oh'
     else:
         CFLAGS += ' -Oh'
 
diff --git a/bsp/stm32/stm32l053-st-nucleo/board/Kconfig b/bsp/stm32/stm32l053-st-nucleo/board/Kconfig
index febe9f5527..cc948cfbc8 100644
--- a/bsp/stm32/stm32l053-st-nucleo/board/Kconfig
+++ b/bsp/stm32/stm32l053-st-nucleo/board/Kconfig
@@ -11,6 +11,7 @@ menu "Onboard Peripheral Drivers"
 
     config BSP_USING_USB_TO_USART
         bool "Enable USB TO USART (uart2)"
+        select BSP_USING_UART
         select BSP_USING_UART2
         default y
 
diff --git a/bsp/stm32/stm32l053-st-nucleo/rtconfig.py b/bsp/stm32/stm32l053-st-nucleo/rtconfig.py
index 79558e8877..8eeff0e7be 100644
--- a/bsp/stm32/stm32l053-st-nucleo/rtconfig.py
+++ b/bsp/stm32/stm32l053-st-nucleo/rtconfig.py
@@ -52,7 +52,7 @@ if PLATFORM == 'gcc':
     LPATH = ''
 
     if BUILD == 'debug':
-        CFLAGS += ' -O0 -gdwarf-2 -g'
+        CFLAGS += ' -O2 -gdwarf-2 -g'
         AFLAGS += ' -gdwarf-2'
     else:
         CFLAGS += ' -O2'
@@ -83,7 +83,7 @@ elif PLATFORM == 'armcc':
     EXEC_PATH += '/ARM/ARMCC/bin/'
 
     if BUILD == 'debug':
-        CFLAGS += ' -g -O0'
+        CFLAGS += ' -g -O2'
         AFLAGS += ' -g'
     else:
         CFLAGS += ' -O2'
@@ -164,7 +164,7 @@ elif PLATFORM == 'iar':
 
     if BUILD == 'debug':
         CFLAGS += ' --debug'
-        CFLAGS += ' -On'
+        CFLAGS += ' -Oh'
     else:
         CFLAGS += ' -Oh'