diff --git a/Libraries/BSP/Src/py32f0xx_bsp_printf.c b/Libraries/BSP/Src/py32f0xx_bsp_printf.c
index 48db868..b26b762 100644
--- a/Libraries/BSP/Src/py32f0xx_bsp_printf.c
+++ b/Libraries/BSP/Src/py32f0xx_bsp_printf.c
@@ -4,6 +4,8 @@
 #include "py32f0xx_bsp_printf.h"
 
 #ifdef HAL_UART_MODULE_ENABLED
+UART_HandleTypeDef DebugUartHandle;
+
 /**
   * @brief  DEBUG_USART GPIO Config,Mode Config,115200 8-N-1
   * @param  None
diff --git a/Makefile b/Makefile
index 40b5816..a2758f6 100644
--- a/Makefile
+++ b/Makefile
@@ -7,14 +7,16 @@ BUILD_DIR		= Build
 
 ##### Options #####
 
+# Enable printf float %f support, y:yes, n:no
+ENABLE_PRINTF_FLOAT	?= n
 # Programmer, jlink or pyocd
 FLASH_PROGRM	?= pyocd
 
 ##### Toolchains #######
 
 #ARM_TOOCHAIN	?= /opt/gcc-arm/gcc-arm-11.2-2022.02-x86_64-arm-none-eabi/bin
-ARM_TOOCHAIN	?= /opt/gcc-arm/arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin
-#ARM_TOOCHAIN	?= /opt/gcc-arm/arm-gnu-toolchain-12.2.mpacbti-bet1-x86_64-arm-none-eabi/bin
+#ARM_TOOCHAIN	?= /opt/gcc-arm/arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin
+ARM_TOOCHAIN	?= /opt/gcc-arm/arm-gnu-toolchain-12.2.mpacbti-bet1-x86_64-arm-none-eabi/bin
 
 # path to JLinkExe
 JLINKEXE		?= /opt/SEGGER/JLink/JLinkExe
@@ -37,8 +39,7 @@ LIB_FLAGS       = PY32F003x8
 CDIRS	:= User \
 		Libraries/CMSIS/Device/PY32F0xx/Source \
 		Libraries/PY32F0xx_HAL_Driver/Src \
-		Libraries/BSP/Src \
-		Libraries/BSP/PY32F003xx_Start_Kit
+		Libraries/BSP/Src
 # C source files (if there are any single ones)
 CFILES := 
 
@@ -52,7 +53,6 @@ INCLUDES	:= Libraries/CMSIS/Include \
 			Libraries/CMSIS/Device/PY32F0xx/Include \
 			Libraries/PY32F0xx_HAL_Driver/Inc \
 			Libraries/BSP/Inc \
-			Libraries/BSP/PY32F003xx_Start_Kit \
 			User
 
 include ./rules.mk
diff --git a/rules.mk b/rules.mk
index f05360f..8da933f 100644
--- a/rules.mk
+++ b/rules.mk
@@ -15,11 +15,11 @@ TOP			= .
 BDIR		= $(TOP)/$(BUILD_DIR)
 
 # For each direcotry, add it to csources
-CSOURCES := $(foreach dir, $(CDIRS), $(shell find $(TOP)/$(dir) -name '*.c'))
+CSOURCES := $(foreach dir, $(CDIRS), $(shell find $(TOP)/$(dir) -maxdepth 1 -name '*.c'))
 # Add single c source files to csources
 CSOURCES += $(addprefix $(TOP)/, $(CFILES))
 # Then assembly source folders and files
-ASOURCES := $(foreach dir, $(ADIRS), $(shell find $(TOP)/$(dir) -name '*.s'))
+ASOURCES := $(foreach dir, $(ADIRS), $(shell find $(TOP)/$(dir) -maxdepth 1 -name '*.s'))
 ASOURCES += $(addprefix $(TOP)/, $(AFILES))
 
 # Fill object files with c and asm files (keep source directory structure)
@@ -28,32 +28,35 @@ OBJS += $(ASOURCES:$(TOP)/%.s=$(BDIR)/%.o)
 # d files for detecting h file changes
 DEPS=$(CSOURCES:$(TOP)/%.c=$(BDIR)/%.d)
 
-# Global compile flags
-CFLAGS		= -Wall -ggdb -ffunction-sections -fdata-sections
-ASFLAGS		= -g -Wa,--warn
-
 # Arch and target specified flags
-OPT			?= -Os
+ARCH_FLAGS	:= -mthumb -mcpu=cortex-m0plus
+# Debug options, -gdwarf-2 for debug, -g0 for release 
+# https://gcc.gnu.org/onlinedocs/gcc-12.2.0/gcc/Debugging-Options.html
+#  -g: system’s native format, -g0:off, -g/g1,-g2,-g3 -> more verbosely
+#  -ggdb: for gdb, -ggdb0:off, -ggdb/ggdb1,-ggdb2,-ggdb3 -> more verbosely
+#  -gdwarf: in DWARF format, -gdwarf-2,-gdwarf-3,-gdwarf-4,-gdwarf-5
+DEBUG_FLAGS ?= -gdwarf-3
+
+# c flags
+OPT			?= -O3
 CSTD		?= -std=c99
-ARCH_FLAGS	:= -fno-common -mcpu=cortex-m0plus -mthumb
+TGT_CFLAGS 	+= $(ARCH_FLAGS) $(DEBUG_FLAGS) $(OPT) $(CSTD) $(addprefix -D, $(LIB_FLAGS)) -Wall -ffunction-sections -fdata-sections
 
-### c flags ###
-TGT_CFLAGS 	+= $(ARCH_FLAGS) $(addprefix -D, $(LIB_FLAGS))
+# asm flags
+TGT_ASFLAGS += $(ARCH_FLAGS) $(DEBUG_FLAGS) $(OPT) -Wa,--warn
 
-### asm flags ###
-TGT_ASFLAGS += $(ARCH_FLAGS)
+# ld flags
+TGT_LDFLAGS += $(ARCH_FLAGS) -specs=nano.specs -specs=nosys.specs -static -lc -lm \
+				-Wl,-Map=$(BDIR)/$(PROJECT).map \
+				-Wl,--gc-sections \
+				-Wl,--print-memory-usage \
+				-Wl,--no-warn-rwx-segments
 
-### ld flags ###
-TGT_LDFLAGS += --specs=nosys.specs -mcpu=cortex-m0plus -mthumb -Wl,--gc-sections -Wl,-Map=$(BDIR)/$(PROJECT).map -Wl,--print-memory-usage
- # Use newlib-nano instead of newlib for smaller flash size
-TGT_LDFLAGS += --specs=nano.specs
- # Exclude standard initialization actions, when __libc_init_array exists, this should be omit, \
-   otherwise it will generate "undefined reference to `_init'" error. \
-   **Remove** `bl __libc_init_array` from startup.s if you want to enable this.
-# TGT_LDFLAGS += -nostartfiles
+ifeq ($(ENABLE_PRINTF_FLOAT),y)
+TGT_LDFLAGS	+= -u _printf_float
+endif
 
-
-### included paths ###
+# include paths
 TGT_INCFLAGS := $(addprefix -I $(TOP)/, $(INCLUDES))
 
 
@@ -76,18 +79,18 @@ echo:
 $(BDIR)/%.o: %.c
 	@printf "  CC\t$<\n"
 	@mkdir -p $(dir $@)
-	$(Q)$(CC) $(TGT_CFLAGS) $(OPT) $(CFLAGS) $(TGT_INCFLAGS) -MT $@ -MMD -MP -MF $(BDIR)/$*.d -o $@ -c $< 
+	$(Q)$(CC) $(TGT_CFLAGS) $(TGT_INCFLAGS) -MT $@ -o $@ -c $< -MD -MF $(BDIR)/$*.d -MP
 
 # Compile asm to obj
 $(BDIR)/%.o: %.s
 	@printf "  AS\t$<\n"
 	@mkdir -p $(dir $@)
-	$(Q)$(CC) $(TGT_ASFLAGS) $(ASFLAGS) -o $@ -c $<
+	$(Q)$(CC) $(TGT_ASFLAGS) -o $@ -c $<
 
 # Link object files to elf
 $(BDIR)/$(PROJECT).elf: $(OBJS) $(TOP)/$(LDSCRIPT)
 	@printf "  LD\t$@\n"
-	$(Q)$(CC) $(OBJS) $(TGT_LDFLAGS) -T$(TOP)/$(LDSCRIPT) -o $@
+	$(Q)$(CC) $(TGT_LDFLAGS) -T$(TOP)/$(LDSCRIPT) $(OBJS) -o $@
 
 # Convert elf to bin
 %.bin: %.elf