diff --git a/Makefile b/Makefile
index 69a4a36..0bac133 100644
--- a/Makefile
+++ b/Makefile
@@ -51,19 +51,17 @@ DEPENDENCIES = $(patsubst %,%.inc,$(FIRMWARE))
 -include $(DEPENDENCIES)
 
 # executables for linking, compiling, debugging, ...
-# use ELLCC cross-compiling chain (based on clang/llvm + musl)
-ELLCC := /opt/ellcc/
+# use clang to compile, GNU ARM toolchain for the rest
+PREFIX ?= arm-none-eabi
 # use ELLCC as compile
-CC := $(ELLCC)bin/ecc -target arm-none-eabi
+CC := clang -target $(PREFIX)
 LD := $(PREFIX)-ld
-LD := $(ELLCC)bin/ecc-ld -m armelf
-AR := $(ELLCC)bin/ecc-ar
-AS := $(ELLCC)bin/ecc-as
-OBJCOPY := $(ELLCC)bin/ecc-objcopy
-OBJDUMP := $(ELLCC)bin/ecc-objdump
-GDB := $(ELLCC)bin/ecc-gdb
-# ecc-gdb (0.13.3) is buggy (crash on kill, can't load elf)
-GDB := arm-none-eabi-gdb
+LD := $(PREFIX)-ld
+AR := $(PREFIX)-ar
+AS := $(PREFIX)-as
+OBJCOPY := $(PREFIX)-objcopy
+OBJDUMP := $(PREFIX)-objdump
+GDB := $(PREFIX)-gdb
 
 # device micro-controller and board
 DEFS += -DSTM32F1 -D$(BOARD)
@@ -79,16 +77,14 @@ CFLAGS += -std=c99
 CFLAGS += -Wpedantic -Wall -Werror -Wundef -Wextra -Wshadow -Wredundant-decls -Wmissing-prototypes -Wstrict-prototypes -Wstrict-overflow=5
 # add options for better code optimization
 CFLAGS += -fno-common -ffunction-sections -fdata-sections
-# use variable size enum (opencm3, gcc, and compiler-rt do)
-#CFLAGS += -fshort-enums
+# use variable size enum (clang doesn't but opencm3, and gcc do)
+CFLAGS += -fshort-enums
 # use no variable size enum (ELLCC/musl does not)
-CFLAGS += -fno-short-enums
+#CFLAGS += -fno-short-enums
 # don't use system main definition (the starting point)
 CFLAGS += -ffreestanding
-# don't use the standard library
-CFLAGS += -nostdlib -nostdinc
-# include ELLCC libraries
-CFLAGS += -I $(ELLCC)libecc/include/ -I $(ELLCC)libecc/include/arm/
+# don't use the standard library (only if you provide an alternative libc library)
+#CFLAGS += -nostdlib -nostdinc
 # include own libraries 
 CFLAGS += $(foreach lib,$(SRCLIBS),-I $(lib))
 # include opencm3 libraries
@@ -103,16 +99,17 @@ LDFLAGS += -static
 LDFLAGS += -nostartfiles
 # only keep used sections
 LDFLAGS += --gc-sections
-# don't use system libraries
-LDFLAGS += -nostdlib -nostdinc
-# add ELLCC standard libraries (for libc, libm, libgcc)
-LDFLAGS += --library-path $(ELLCC)libecc/lib/cortex-m3-linux/
+# don't use system libraries (only if you provide an alternative libc library)
+#LDFLAGS += -nostdlib -nostdinc
+# add standard libraries (for libc, libm, libnosys, libgcc)
+LDFLAGS += --library-path /usr/arm-none-eabi/lib/armv7-m/
+LDFLAGS += --library-path /usr/lib/gcc/arm-none-eabi/*/armv7-m/
 # opencm3 libraries
 LDFLAGS += --library-path $(OPENCM3_LIB)
-# used libraries (gcc provides the ARM ABI, not sure how to replace with compiler-rt)
-LDLIBS += --library $(STM32F1_LIB) --library c --library m --library gcc
+# used libraries (gcc provides the ARM ABI)
+LDLIBS += --library $(STM32F1_LIB) --library c --library m --library nosys --library gcc
 
-# target micro-controller information (ARM Cortex-M3 supports thumb and thumnb2, but does not include a floating point unit)
+# target micro-controller information (ARM Cortex-M3 supports thumb and thumb2, but does not include a floating point unit)
 ARCH_FLAGS = -mthumb -mcpu=cortex-m3 -msoft-float
 
 # SWD adapter used
@@ -177,7 +174,7 @@ $(OPENCM3_DIR)/Makefile:
 # compile libopencm3
 $(OPENCM3_LIB)/lib$(STM32F1_LIB).a: $(OPENCM3_DIR)/Makefile
 	$(info compiling libopencm3 submodule)
-	$(Q)CFLAGS=-fno-short-enums $(MAKE) --directory $(OPENCM3_DIR)
+	$(Q)$(MAKE) --directory $(OPENCM3_DIR)
 
 # doxygen documentation
 doc: Doxyfile README.md $(patsubst %,%.c,$(FIRMWARE)) $(CSRC) $(CHDR)