diff --git a/examples/build_system/make/cpu/cortex-m0.mk b/examples/build_system/make/cpu/cortex-m0.mk
index feb0f395b..c2c33a2ee 100644
--- a/examples/build_system/make/cpu/cortex-m0.mk
+++ b/examples/build_system/make/cpu/cortex-m0.mk
@@ -4,10 +4,18 @@ ifeq ($(TOOLCHAIN),gcc)
     -mcpu=cortex-m0 \
     -mfloat-abi=soft \
 
+else ifeq ($(TOOLCHAIN),clang)
+  CFLAGS += \
+	  --target=arm-none-eabi \
+	  -mcpu=cortex-m0 \
+
 else ifeq ($(TOOLCHAIN),iar)
   # IAR Flags
   CFLAGS += --cpu cortex-m0
   ASFLAGS += --cpu cortex-m0
+
+else
+  $(error "TOOLCHAIN is not supported")
 endif
 
 # For freeRTOS port source
diff --git a/examples/build_system/make/cpu/cortex-m0plus.mk b/examples/build_system/make/cpu/cortex-m0plus.mk
index b416b7a4a..fe8feb227 100644
--- a/examples/build_system/make/cpu/cortex-m0plus.mk
+++ b/examples/build_system/make/cpu/cortex-m0plus.mk
@@ -4,10 +4,18 @@ ifeq ($(TOOLCHAIN),gcc)
     -mcpu=cortex-m0plus \
     -mfloat-abi=soft \
 
+else ifeq ($(TOOLCHAIN),clang)
+  CFLAGS += \
+	  --target=arm-none-eabi \
+	  -mcpu=cortex-m0plus \
+
 else ifeq ($(TOOLCHAIN),iar)
   # IAR Flags
   CFLAGS += --cpu cortex-m0+
   ASFLAGS += --cpu cortex-m0+
+
+else
+  $(error "TOOLCHAIN is not supported")
 endif
 
 # For freeRTOS port source
diff --git a/examples/build_system/make/cpu/cortex-m23.mk b/examples/build_system/make/cpu/cortex-m23.mk
index 29542d8e8..7ab758352 100644
--- a/examples/build_system/make/cpu/cortex-m23.mk
+++ b/examples/build_system/make/cpu/cortex-m23.mk
@@ -4,10 +4,18 @@ ifeq ($(TOOLCHAIN),gcc)
     -mcpu=cortex-m23 \
     -mfloat-abi=soft \
 
+else ifeq ($(TOOLCHAIN),clang)
+  CFLAGS += \
+	  --target=arm-none-eabi \
+	  -mcpu=cortex-m23 \
+
 else ifeq ($(TOOLCHAIN),iar)
   # IAR Flags
   CFLAGS += --cpu cortex-m23
   ASFLAGS += --cpu cortex-m23
+
+else
+  $(error "TOOLCHAIN is not supported")
 endif
 
 # For freeRTOS port source
diff --git a/examples/build_system/make/cpu/cortex-m3.mk b/examples/build_system/make/cpu/cortex-m3.mk
index 7a34b9e04..b6325313f 100644
--- a/examples/build_system/make/cpu/cortex-m3.mk
+++ b/examples/build_system/make/cpu/cortex-m3.mk
@@ -4,13 +4,18 @@ ifeq ($(TOOLCHAIN),gcc)
     -mcpu=cortex-m3 \
     -mfloat-abi=soft \
 
+else ifeq ($(TOOLCHAIN),clang)
+  CFLAGS += \
+	  --target=arm-none-eabi \
+	  -mcpu=cortex-m3 \
+
 else ifeq ($(TOOLCHAIN),iar)
   # IAR Flags
-  CFLAGS += \
-    --cpu cortex-m3 \
+  CFLAGS += --cpu cortex-m3
+  ASFLAGS += --cpu cortex-m3
 
-  ASFLAGS += \
-     --cpu cortex-m3
+else
+  $(error "TOOLCHAIN is not supported")
 endif
 
 # For freeRTOS port source
diff --git a/examples/build_system/make/cpu/cortex-m33-nodsp-nofp.mk b/examples/build_system/make/cpu/cortex-m33-nodsp-nofp.mk
index c65f24376..405053dd0 100644
--- a/examples/build_system/make/cpu/cortex-m33-nodsp-nofp.mk
+++ b/examples/build_system/make/cpu/cortex-m33-nodsp-nofp.mk
@@ -1,16 +1,24 @@
 ifeq ($(TOOLCHAIN),gcc)
-	CFLAGS += \
+  CFLAGS += \
 	-mthumb \
 	-mcpu=cortex-m33+nodsp \
 	-mfloat-abi=soft \
 
+else ifeq ($(TOOLCHAIN),clang)
+  CFLAGS += \
+	  --target=arm-none-eabi \
+	  -mcpu=cortex-m33 \
+	  -mfpu=softvp \
+
 else ifeq ($(TOOLCHAIN),iar)
-	CFLAGS += \
+  CFLAGS += \
 		--cpu cortex-m33+nodsp \
 
-	ASFLAGS += \
+  ASFLAGS += \
 		--cpu cortex-m33+nodsp \
 
+else
+  $(error "TOOLCHAIN is not supported")
 endif
 
 FREERTOS_PORTABLE_SRC ?= $(FREERTOS_PORTABLE_PATH)/ARM_CM33_NTZ/non_secure
diff --git a/examples/build_system/make/cpu/cortex-m33.mk b/examples/build_system/make/cpu/cortex-m33.mk
index fe5b7b380..47b0eaecd 100644
--- a/examples/build_system/make/cpu/cortex-m33.mk
+++ b/examples/build_system/make/cpu/cortex-m33.mk
@@ -5,15 +5,23 @@ ifeq ($(TOOLCHAIN),gcc)
     -mfloat-abi=hard \
     -mfpu=fpv5-sp-d16 \
 
+else ifeq ($(TOOLCHAIN),clang)
+  CFLAGS += \
+	  --target=arm-none-eabi \
+	  -mcpu=cortex-m33 \
+	  -mfpu=fpv5-sp-d16 \
+
 else ifeq ($(TOOLCHAIN),iar)
-	CFLAGS += \
+  CFLAGS += \
 		--cpu cortex-m33 \
 		--fpu VFPv5-SP \
 
-	ASFLAGS += \
+  ASFLAGS += \
 		--cpu cortex-m33 \
 		--fpu VFPv5-SP \
 
+else
+  $(error "TOOLCHAIN is not supported")
 endif
 
 FREERTOS_PORTABLE_SRC ?= $(FREERTOS_PORTABLE_PATH)/ARM_CM33_NTZ/non_secure
diff --git a/examples/build_system/make/cpu/cortex-m4.mk b/examples/build_system/make/cpu/cortex-m4.mk
index d8776b5d8..4e16819d1 100644
--- a/examples/build_system/make/cpu/cortex-m4.mk
+++ b/examples/build_system/make/cpu/cortex-m4.mk
@@ -5,9 +5,18 @@ ifeq ($(TOOLCHAIN),gcc)
     -mfloat-abi=hard \
     -mfpu=fpv4-sp-d16 \
 
+else ifeq ($(TOOLCHAIN),clang)
+  CFLAGS += \
+	  --target=arm-none-eabi \
+	  -mcpu=cortex-m4 \
+	  -mfpu=fpv4-sp-d16 \
+
 else ifeq ($(TOOLCHAIN),iar)
   CFLAGS += --cpu cortex-m4 --fpu VFPv4
   ASFLAGS += --cpu cortex-m4 --fpu VFPv4
+
+else
+  $(error "TOOLCHAIN is not supported")
 endif
 
 FREERTOS_PORTABLE_SRC ?= $(FREERTOS_PORTABLE_PATH)/ARM_CM4F
diff --git a/examples/build_system/make/cpu/cortex-m7.mk b/examples/build_system/make/cpu/cortex-m7.mk
index 0e3461787..3e6116179 100644
--- a/examples/build_system/make/cpu/cortex-m7.mk
+++ b/examples/build_system/make/cpu/cortex-m7.mk
@@ -5,6 +5,12 @@ ifeq ($(TOOLCHAIN),gcc)
     -mfloat-abi=hard \
     -mfpu=fpv5-d16 \
 
+else ifeq ($(TOOLCHAIN),clang)
+  CFLAGS += \
+	  --target=arm-none-eabi \
+	  -mcpu=cortex-m7 \
+	  -mfpu=fpv5-d16 \
+
 else ifeq ($(TOOLCHAIN),iar)
   CFLAGS += \
   	--cpu cortex-m7 \
@@ -14,6 +20,8 @@ else ifeq ($(TOOLCHAIN),iar)
 		--cpu cortex-m7 \
 		--fpu VFPv5_D16 \
 
+else
+  $(error "TOOLCHAIN is not supported")
 endif
 
 FREERTOS_PORTABLE_SRC ?= $(FREERTOS_PORTABLE_PATH)/ARM_CM7/r0p1
diff --git a/examples/build_system/make/cpu/msp430.mk b/examples/build_system/make/cpu/msp430.mk
index 06340d23b..6daa2c38d 100644
--- a/examples/build_system/make/cpu/msp430.mk
+++ b/examples/build_system/make/cpu/msp430.mk
@@ -1,7 +1,11 @@
 ifeq ($(TOOLCHAIN),gcc)
   # nothing to add
+else ifeq ($(TOOLCHAIN),clang)
+  # nothing to add
 else ifeq ($(TOOLCHAIN),iar)
   # nothing to add
+else
+  $(error "TOOLCHAIN is not supported")
 endif
 
 # For freeRTOS port source
diff --git a/examples/build_system/make/make.mk b/examples/build_system/make/make.mk
index 2437b8766..1ec42cb50 100644
--- a/examples/build_system/make/make.mk
+++ b/examples/build_system/make/make.mk
@@ -2,6 +2,26 @@
 # Common make definition for all examples
 # ---------------------------------------
 
+#-------------------------------------------------------------
+# Toolchain
+# Can be changed via TOOLCHAIN=gcc|iar or CC=arm-none-eabi-gcc|iccarm|clang
+#-------------------------------------------------------------
+
+ifneq (,$(findstring clang,$(CC)))
+  TOOLCHAIN = clang
+else ifneq (,$(findstring iccarm,$(CC)))
+  TOOLCHAIN = iar
+else ifneq (,$(findstring gcc,$(CC)))
+  TOOLCHAIN = gcc
+endif
+
+# Default to GCC
+ifndef TOOLCHAIN
+  TOOLCHAIN = gcc
+endif
+
+$(info TOOLCHAIN: $(TOOLCHAIN))
+
 #-------------- TOP and CURRENT_PATH ------------
 
 # Set TOP to be the path to get from the current directory (where make was invoked) to the top of the tree.
@@ -75,12 +95,6 @@ else
   SRC_C += $(subst $(TOP)/,,$(wildcard $(TOP)/$(FAMILY_PATH)/*.c))
 endif
 
-#-------------------------------------------------------------
-# Toolchain
-# Can be changed via TOOLCHAIN=gcc|iar or CC=arm-none-eabi-gcc|iccarm|clang
-#-------------------------------------------------------------
-TOOLCHAIN ?= gcc
-
 #-------------- Source files and compiler flags --------------
 # tinyusb makefile
 include $(TOP)/src/tinyusb.mk
@@ -112,7 +126,7 @@ endif
 
 # Logger: default is uart, can be set to rtt or swo
 ifneq ($(LOGGER),)
-	CMAKE_DEFSYM +=	-DLOGGER=$(LOGGER)
+  CMAKE_DEFSYM +=	-DLOGGER=$(LOGGER)
 endif
 
 ifeq ($(LOGGER),rtt)
diff --git a/examples/build_system/make/rules.mk b/examples/build_system/make/rules.mk
index 78fce49d2..7b6b339ed 100644
--- a/examples/build_system/make/rules.mk
+++ b/examples/build_system/make/rules.mk
@@ -24,7 +24,7 @@ vpath %.c . $(TOP)
 vpath %.s . $(TOP)
 vpath %.S . $(TOP)
 
-include ${TOP}/examples/build_system/make/toolchain/arm_$(TOOLCHAIN)_rules.mk
+include ${TOP}/examples/build_system/make/toolchain/$(TOOLCHAIN)_rules.mk
 
 # ---------------------------------------
 # Compiler Flags
diff --git a/examples/build_system/make/toolchain/arm_clang.mk b/examples/build_system/make/toolchain/arm_clang.mk
new file mode 100644
index 000000000..97face39c
--- /dev/null
+++ b/examples/build_system/make/toolchain/arm_clang.mk
@@ -0,0 +1,10 @@
+CC = clang
+CXX = clang++
+AS = $(CC) -x assembler-with-cpp
+LD = $(CC)
+
+GDB = $(CROSS_COMPILE)gdb
+OBJCOPY = llvm-objcopy
+SIZE = llvm-size
+
+include ${TOP}/examples/build_system/make/toolchain/gcc_common.mk
diff --git a/examples/build_system/make/toolchain/arm_gcc.mk b/examples/build_system/make/toolchain/arm_gcc.mk
index c34581ae2..a8576f8ee 100644
--- a/examples/build_system/make/toolchain/arm_gcc.mk
+++ b/examples/build_system/make/toolchain/arm_gcc.mk
@@ -12,73 +12,9 @@ GDB = $(CROSS_COMPILE)gdb
 OBJCOPY = $(CROSS_COMPILE)objcopy
 SIZE = $(CROSS_COMPILE)size
 
-CC_VERSION := $(shell $(CC) -dumpversion)
-CC_VERSION_MAJOR = $(firstword $(subst ., ,$(CC_VERSION)))
-
-# ---------------------------------------
-# Compiler Flags
-# ---------------------------------------
 CFLAGS += \
-  -MD \
-  -ggdb \
-  -fdata-sections \
-  -ffunction-sections \
   -fsingle-precision-constant \
-  -fno-strict-aliasing \
-  -Wall \
-  -Wextra \
-  -Werror \
-  -Wfatal-errors \
-  -Wdouble-promotion \
-  -Wstrict-prototypes \
-  -Wstrict-overflow \
-  -Werror-implicit-function-declaration \
-  -Wfloat-equal \
-  -Wundef \
-  -Wshadow \
-  -Wwrite-strings \
-  -Wsign-compare \
-  -Wmissing-format-attribute \
-  -Wunreachable-code \
-  -Wcast-align \
-  -Wcast-function-type \
-  -Wcast-qual \
-  -Wnull-dereference \
-  -Wuninitialized \
-  -Wunused \
-  -Wreturn-type \
-  -Wredundant-decls \
 
-# conversion is too strict for most mcu driver, may be disable sign/int/arith-conversion
-#  -Wconversion
+LIBS += -lgcc -lm -lnosys
 
-# Size Optimization as default
-CFLAGS_OPTIMIZED ?= -Os
-
-# Debugging/Optimization
-ifeq ($(DEBUG), 1)
-  CFLAGS += -O0
-  NO_LTO = 1
-else
-  CFLAGS += $(CFLAGS_OPTIMIZED)
-endif
-
-# ---------------------------------------
-# Linker Flags
-# ---------------------------------------
-LDFLAGS += \
-  -Wl,-Map=$@.map \
-  -Wl,-cref \
-  -Wl,-gc-sections \
-
-# renesas rx does not support --print-memory-usage flags
-ifneq ($(FAMILY),rx)
-LDFLAGS += -Wl,--print-memory-usage
-endif
-
-# from version 12
-ifeq ($(strip $(if $(CMDEXE),\
-               $(shell if $(CC_VERSION_MAJOR) geq 12 (echo 1) else (echo 0)),\
-               $(shell expr $(CC_VERSION_MAJOR) \>= 12))), 1)
-LDFLAGS += -Wl,--no-warn-rwx-segment
-endif
+include ${TOP}/examples/build_system/make/toolchain/gcc_common.mk
diff --git a/examples/build_system/make/toolchain/clang_rules.mk b/examples/build_system/make/toolchain/clang_rules.mk
new file mode 100644
index 000000000..341f705b1
--- /dev/null
+++ b/examples/build_system/make/toolchain/clang_rules.mk
@@ -0,0 +1 @@
+include ${TOP}/examples/build_system/make/toolchain/gcc_rules.mk
diff --git a/examples/build_system/make/toolchain/gcc_common.mk b/examples/build_system/make/toolchain/gcc_common.mk
new file mode 100644
index 000000000..6986d8bba
--- /dev/null
+++ b/examples/build_system/make/toolchain/gcc_common.mk
@@ -0,0 +1,71 @@
+# ---------------------------------------
+# Compiler Flags
+# ---------------------------------------
+CFLAGS += \
+  -MD \
+  -ggdb \
+  -fdata-sections \
+  -ffunction-sections \
+  -fno-strict-aliasing \
+  -Wall \
+  -Wextra \
+  -Werror \
+  -Wfatal-errors \
+  -Wdouble-promotion \
+  -Wstrict-prototypes \
+  -Wstrict-overflow \
+  -Werror-implicit-function-declaration \
+  -Wfloat-equal \
+  -Wundef \
+  -Wshadow \
+  -Wwrite-strings \
+  -Wsign-compare \
+  -Wmissing-format-attribute \
+  -Wunreachable-code \
+  -Wcast-align \
+  -Wcast-function-type \
+  -Wcast-qual \
+  -Wnull-dereference \
+  -Wuninitialized \
+  -Wunused \
+  -Wreturn-type \
+  -Wredundant-decls \
+
+# conversion is too strict for most mcu driver, may be disable sign/int/arith-conversion
+#  -Wconversion
+
+# Size Optimization as default
+CFLAGS_OPTIMIZED ?= -Os
+
+# Debugging/Optimization
+ifeq ($(DEBUG), 1)
+  CFLAGS += -O0
+  NO_LTO = 1
+else
+  CFLAGS += $(CFLAGS_OPTIMIZED)
+endif
+
+# ---------------------------------------
+# Linker Flags
+# ---------------------------------------
+LDFLAGS += \
+  -Wl,-Map=$@.map \
+  -Wl,--cref \
+  -Wl,-gc-sections \
+
+# renesas rx does not support --print-memory-usage flags
+ifneq ($(FAMILY),rx)
+LDFLAGS += -Wl,--print-memory-usage
+endif
+
+ifeq ($(TOOLCHAIN),gcc)
+CC_VERSION := $(shell $(CC) -dumpversion)
+CC_VERSION_MAJOR = $(firstword $(subst ., ,$(CC_VERSION)))
+
+# from version 12
+ifeq ($(strip $(if $(CMDEXE),\
+               $(shell if $(CC_VERSION_MAJOR) geq 12 (echo 1) else (echo 0)),\
+               $(shell expr $(CC_VERSION_MAJOR) \>= 12))), 1)
+LDFLAGS += -Wl,--no-warn-rwx-segment
+endif
+endif
diff --git a/examples/build_system/make/toolchain/arm_gcc_rules.mk b/examples/build_system/make/toolchain/gcc_rules.mk
similarity index 92%
rename from examples/build_system/make/toolchain/arm_gcc_rules.mk
rename to examples/build_system/make/toolchain/gcc_rules.mk
index d295879d9..3cd87db64 100644
--- a/examples/build_system/make/toolchain/arm_gcc_rules.mk
+++ b/examples/build_system/make/toolchain/gcc_rules.mk
@@ -21,8 +21,13 @@ ifneq ($(CFLAGS_SKIP),)
 CFLAGS := $(filter-out $(CFLAGS_SKIP),$(CFLAGS))
 endif
 
+ifeq ($(TOOLCHAIN),clang)
+LDFLAGS += $(CFLAGS) $(LDFLAGS_CLANG)
+else
 LDFLAGS += $(CFLAGS) $(LDFLAGS_GCC)
+endif
 
+# TODO should be removed after all examples are updated
 ifdef LD_FILE
 LDFLAGS += -Wl,-T,$(TOP)/$(LD_FILE)
 endif
@@ -33,11 +38,7 @@ endif
 
 ASFLAGS += $(CFLAGS)
 
-LIBS_GCC ?= -lgcc -lm -lnosys
-
 # libc
-LIBS += $(LIBS_GCC)
-
 ifneq ($(BOARD), spresense)
 LIBS += -lc
 endif
diff --git a/examples/build_system/make/toolchain/arm_iar_rules.mk b/examples/build_system/make/toolchain/iar_rules.mk
similarity index 100%
rename from examples/build_system/make/toolchain/arm_iar_rules.mk
rename to examples/build_system/make/toolchain/iar_rules.mk
diff --git a/hw/bsp/samd21/family.mk b/hw/bsp/samd21/family.mk
index 3302aade5..309df58fe 100644
--- a/hw/bsp/samd21/family.mk
+++ b/hw/bsp/samd21/family.mk
@@ -6,7 +6,6 @@ CPU_CORE ?= cortex-m0plus
 
 CFLAGS += \
   -flto \
-  -nostdlib -nostartfiles \
   -DCONF_DFLL_OVERWRITE_CALIBRATION=0 \
   -DCFG_TUSB_MCU=OPT_MCU_SAMD21
 
@@ -16,7 +15,11 @@ CFLAGS += -Wno-error=redundant-decls
 # SAM driver is flooded with -Wcast-qual which slow down complication significantly
 CFLAGS_SKIP += -Wcast-qual
 
-LDFLAGS_GCC += -specs=nosys.specs -specs=nano.specs
+LDFLAGS_GCC += \
+  -nostdlib -nostartfiles \
+  -specs=nosys.specs -specs=nano.specs \
+
+LDFLAGS_CLANG +=
 
 SRC_C += \
 	src/portable/microchip/samd/dcd_samd.c \