diff --git a/CMakeLists.txt b/CMakeLists.txt
index a484dd0..b54b0ff 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -26,9 +26,9 @@ add_executable(usbtest src/main.c src/util.c)
 
 set_target_properties(usbtest PROPERTIES SUFFIX .elf)
 
-#add_custom_target(libopencm3 make TARGETS=stm32/f1 -j8 WORKING_DIRECTORY ${LIBOPENCM3_DIR})
+add_custom_target(libopencm3 make TARGETS=stm32/f1 -j8 WORKING_DIRECTORY ${LIBOPENCM3_DIR})
 #link_directories(${LIBOPENCM3_DIR}/lib)
-#target_link_libraries(usbtest PUBLIC ${LIBOPENCM3_DIR}/lib/libopencm3_stm32f1.a)
+target_link_libraries(usbtest PUBLIC ${LIBOPENCM3_DIR}/lib/libopencm3_stm32f1.a)
 
 add_subdirectory(RTT)
 target_link_libraries(usbtest PUBLIC RTT)
diff --git a/README.md b/README.md
index 540caf1..6201ece 100644
--- a/README.md
+++ b/README.md
@@ -8,13 +8,17 @@ First time:
 
 or older cmake:
 
-2. `cmake -S . -B build -DCMAKE_TOOLCHAIN_FILE=toolchain-STM32F1.cmake`
+2. `cmake -S . -B build -DCMAKE_TOOLCHAIN_FILE=toolchain-STM32F1.cmake -G Ninja`
 
-And then to build an `.elf`
+### Build libopencm3
 
-0. `cmake --build build --verbose`
+    cmake --build build --verbose -t libopencm3
 
 
+### Build project elf
+
+    cmake --build build --verbose
+
 ## RTT debug console
 
 run this while `openocd` is running