diff --git a/targets/stm32l442/Makefile b/targets/stm32l442/Makefile
index 54dfb0a..7cc9832 100644
--- a/targets/stm32l442/Makefile
+++ b/targets/stm32l442/Makefile
@@ -1,93 +1,24 @@
-CC=arm-none-eabi-gcc
-CP=arm-none-eabi-objcopy
-SZ=arm-none-eabi-size
-AR=arm-none-eabi-ar
 
-# ST related
-SRC = src/main.c src/init.c src/redirect.c src/flash.c src/rng.c src/led.c src/device.c
-SRC += src/fifo.c src/crypto.c src/attestation.c
-SRC += src/startup_stm32l432xx.s src/system_stm32l4xx.c
-SRC += $(wildcard lib/*.c) $(wildcard lib/usbd/*.c)
+all:
+	$(MAKE) -f application.mk -j8
 
-# FIDO2 lib
-SRC += ../../fido2/util.c ../../fido2/u2f.c ../../fido2/test_power.c
-SRC += ../../fido2/stubs.c ../../fido2/log.c  ../../fido2/ctaphid.c  ../../fido2/ctap.c
-SRC += ../../fido2/ctap_parse.c ../../fido2/main.c
-
-# Crypto libs
-SRC += ../../crypto/sha256/sha256.c ../../crypto/micro-ecc/uECC.c ../../crypto/tiny-AES-c/aes.c
-
-
-OBJ1=$(SRC:.c=.o)
-OBJ=$(OBJ1:.s=.o)
-
-INC = -Isrc/ -Isrc/cmsis/ -Ilib/ -Ilib/usbd/ -I../../fido2/ -I../../fido2/extensions
-INC += -I../../tinycbor/src -I../../crypto/sha256 -I../../crypto/micro-ecc
-INC += -I../../crypto/tiny-AES-c
-
-SEARCH=-L../../tinycbor/lib
-
-LDSCRIPT=stm32l432xx.ld
-
-CFLAGS= $(INC)
-
-TARGET=solo
-HW=-mcpu=cortex-m4 -mfpu=fpv4-sp-d16 -mfloat-abi=hard -mthumb
-
-# Nucleo board
-#CHIP=STM32L432xx
-# Solo
-CHIP=STM32L442xx
-
-DEFINES = -D$(CHIP) -DAES256=1  -DUSE_FULL_LL_DRIVER -DAPP_CONFIG=\"app.h\"
-# DEFINES += -DTEST_SOLO_STM32 -DTEST -DTEST_FIFO=1
-
-CFLAGS=$(INC) -c $(DEFINES)   -Wall -fdata-sections -ffunction-sections $(HW) -g
-LDFLAGS_LIB=$(HW) $(SEARCH) -specs=nano.specs  -specs=nosys.specs  -Wl,--gc-sections -u _printf_float -lnosys
-LDFLAGS=$(HW) $(LDFLAGS_LIB) -T$(LDSCRIPT) -Wl,-Map=$(TARGET).map,--cref -ltinycbor
-
-
-.PRECIOUS: %.o
-
-all: $(TARGET).elf
-	$(SZ) $^
-
-%.o: %.c
-	$(CC) $^ $(HW)  -Os $(CFLAGS) -o $@
-
-../../crypto/micro-ecc/uECC.o: ../../crypto/micro-ecc/uECC.c
-	$(CC) $^ $(HW)  -O3 $(CFLAGS) -o $@
-
-%.o: %.s
-	$(CC) $^ $(HW)  -Os $(CFLAGS) -o $@
-
-%.elf: $(OBJ)
-	$(CC) $^ $(HW) $(LDFLAGS) -o $@
-
-%.hex: %.elf
-	$(CP) -O ihex $^ $(TARGET).hex
-
-bootloader:
-	$(MAKE) -f bootloader.mk
+boot:
+	$(MAKE) -f bootloader.mk -j8
 
 clean:
-	rm -f *.o src/*.o src/*.elf  bootloader/*.o $(OBJ)
+	$(MAKE) -f application.mk clean
+	$(MAKE) -f bootloader.mk clean
 
-flash: $(TARGET).hex
-	# STM32_Programmer_CLI -c port=SWD -halt -e all --readunprotect
-	STM32_Programmer_CLI -c port=SWD -halt  -d $(TARGET).hex -rst
-
-flashall:
-	#$(MAKE) -f bootloader.mk -j8
-	python .\merge_hex.py .\solo.hex .\bootloader.hex all.hex
+flash: solo.hex bootloader.hex
+	python merge_hex.py solo.hex bootloader.hex all.hex
 	STM32_Programmer_CLI -c port=SWD -halt -e all --readunprotect
 	STM32_Programmer_CLI -c port=SWD -halt  -d all.hex -rst
 
-detach:
-	STM32_Programmer_CLI -c port=usb1 -ob nBOOT0=1
+bootloader.hex:
+	echo "You need to build the bootloader first."
+
+solo.hex:
+	echo "You need to build the application first."
 
 cbor:
-	cd ../../tinycbor/ && make clean
-	cd ../../tinycbor/ && make CC="$(CC)" AR=$(AR) \
-LDFLAGS="$(LDFLAGS_LIB)" \
-CFLAGS="$(CFLAGS)"
+	$(MAKE) -f application.mk -j8 cbor
diff --git a/targets/stm32l442/README.md b/targets/stm32l442/README.md
new file mode 100644
index 0000000..3c48ddd
--- /dev/null
+++ b/targets/stm32l442/README.md
@@ -0,0 +1,34 @@
+# STM32L4xx Solo
+
+This documents how to build the firmware for Solo for the STM32L4xx microcontroller.
+
+# Building
+
+First build the cbor library.
+
+```bash
+make cbor
+```
+
+Now build the Solo bootloader.
+
+```
+make boot
+```
+
+Now build the Solo application.
+
+```
+make clean      # remove object files from bootloader, keep bootloader.hex
+make
+```
+
+Merge the two files together.  This script also patches a spot in memory to
+allow the bootloader to boot the application.  This memory spot is later used for
+signed firmware updates.
+
+```
+python merge_hex.py solo.hex bootloader.hex all.hex
+```
+
+You can now program Solo with `all.hex`.
diff --git a/targets/stm32l442/application.mk b/targets/stm32l442/application.mk
new file mode 100644
index 0000000..4ee26e3
--- /dev/null
+++ b/targets/stm32l442/application.mk
@@ -0,0 +1,80 @@
+CC=arm-none-eabi-gcc
+CP=arm-none-eabi-objcopy
+SZ=arm-none-eabi-size
+AR=arm-none-eabi-ar
+
+# ST related
+SRC = src/main.c src/init.c src/redirect.c src/flash.c src/rng.c src/led.c src/device.c
+SRC += src/fifo.c src/crypto.c src/attestation.c
+SRC += src/startup_stm32l432xx.s src/system_stm32l4xx.c
+SRC += $(wildcard lib/*.c) $(wildcard lib/usbd/*.c)
+
+# FIDO2 lib
+SRC += ../../fido2/util.c ../../fido2/u2f.c ../../fido2/test_power.c
+SRC += ../../fido2/stubs.c ../../fido2/log.c  ../../fido2/ctaphid.c  ../../fido2/ctap.c
+SRC += ../../fido2/ctap_parse.c ../../fido2/main.c
+
+# Crypto libs
+SRC += ../../crypto/sha256/sha256.c ../../crypto/micro-ecc/uECC.c ../../crypto/tiny-AES-c/aes.c
+
+
+OBJ1=$(SRC:.c=.o)
+OBJ=$(OBJ1:.s=.o)
+
+INC = -Isrc/ -Isrc/cmsis/ -Ilib/ -Ilib/usbd/ -I../../fido2/ -I../../fido2/extensions
+INC += -I../../tinycbor/src -I../../crypto/sha256 -I../../crypto/micro-ecc
+INC += -I../../crypto/tiny-AES-c
+
+SEARCH=-L../../tinycbor/lib
+
+LDSCRIPT=stm32l432xx.ld
+
+CFLAGS= $(INC)
+
+TARGET=solo
+HW=-mcpu=cortex-m4 -mfpu=fpv4-sp-d16 -mfloat-abi=hard -mthumb
+
+# Nucleo board
+#CHIP=STM32L432xx
+# Solo
+CHIP=STM32L442xx
+
+DEFINES = -D$(CHIP) -DAES256=1  -DUSE_FULL_LL_DRIVER -DAPP_CONFIG=\"app.h\"
+# DEFINES += -DTEST_SOLO_STM32 -DTEST -DTEST_FIFO=1
+
+CFLAGS=$(INC) -c $(DEFINES)   -Wall -fdata-sections -ffunction-sections $(HW) -g
+LDFLAGS_LIB=$(HW) $(SEARCH) -specs=nano.specs  -specs=nosys.specs  -Wl,--gc-sections -u _printf_float -lnosys
+LDFLAGS=$(HW) $(LDFLAGS_LIB) -T$(LDSCRIPT) -Wl,-Map=$(TARGET).map,--cref -ltinycbor
+
+
+.PRECIOUS: %.o
+
+all: $(TARGET).elf
+	$(SZ) $^
+
+%.o: %.c
+	$(CC) $^ $(HW)  -Os $(CFLAGS) -o $@
+
+../../crypto/micro-ecc/uECC.o: ../../crypto/micro-ecc/uECC.c
+	$(CC) $^ $(HW)  -O3 $(CFLAGS) -o $@
+
+%.o: %.s
+	$(CC) $^ $(HW)  -Os $(CFLAGS) -o $@
+
+%.elf: $(OBJ)
+	$(CC) $^ $(HW) $(LDFLAGS) -o $@
+
+%.hex: %.elf
+	$(CP) -O ihex $^ $(TARGET).hex
+
+clean:
+	rm -f *.o src/*.o src/*.elf  bootloader/*.o $(OBJ)
+
+detach:
+	STM32_Programmer_CLI -c port=usb1 -ob nBOOT0=1
+
+cbor:
+	cd ../../tinycbor/ && make clean
+	cd ../../tinycbor/ && make CC="$(CC)" AR=$(AR) \
+LDFLAGS="$(LDFLAGS_LIB)" \
+CFLAGS="$(CFLAGS)"
diff --git a/targets/stm32l442/bootloader.mk b/targets/stm32l442/bootloader.mk
index b7c2b8b..9aad2b1 100644
--- a/targets/stm32l442/bootloader.mk
+++ b/targets/stm32l442/bootloader.mk
@@ -16,10 +16,10 @@ SRC += ../../fido2/stubs.c ../../fido2/log.c  ../../fido2/ctaphid.c  ../../fido2
 # Crypto libs
 SRC += ../../crypto/sha256/sha256.c ../../crypto/micro-ecc/uECC.c
 
-
 OBJ1=$(SRC:.c=.o)
 OBJ=$(OBJ1:.s=.o)
 
+
 INC = -Ibootloader/ -Isrc/ -Isrc/cmsis/ -Ilib/ -Ilib/usbd/ -I../../fido2/ -I../../fido2/extensions
 INC += -I../../tinycbor/src -I../../crypto/sha256 -I../../crypto/micro-ecc
 INC += -I../../crypto/tiny-AES-c
@@ -49,6 +49,7 @@ LDFLAGS=$(HW) $(LDFLAGS_LIB) -T$(LDSCRIPT) -Wl,-Map=$(TARGET).map,--cref
 all: $(TARGET).elf
 	$(SZ) $^
 
+
 %.o: %.c
 	$(CC) $^ $(HW)  -Os $(CFLAGS) -o $@
 
@@ -66,16 +67,3 @@ all: $(TARGET).elf
 
 clean:
 	rm -f *.o src/*.o bootloader/*.o src/*.elf  $(OBJ)
-
-flash: $(TARGET).hex
-	STM32_Programmer_CLI -c port=SWD -halt -e all --readunprotect
-	STM32_Programmer_CLI -c port=SWD -halt  -d $(TARGET).hex -rst
-
-detach:
-	STM32_Programmer_CLI -c port=usb1 -ob nBOOT0=1
-
-cbor:
-	cd ../../tinycbor/ && make clean
-	cd ../../tinycbor/ && make CC="$(CC)" AR=$(AR) \
-LDFLAGS="$(LDFLAGS_LIB)" \
-CFLAGS="$(CFLAGS)"