diff --git a/CMakeLists.txt b/CMakeLists.txt
index aace54bd66..fcfb877d0a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -56,6 +56,9 @@
 # Functions/Macros
 # ---------------------------------------------------------------------------
 #
+# * Use px4_parse_function_args to parse functions and check for required
+#   arguments.
+#
 # * Never use macros. They allow overwriting global variables and this
 #	makes variable declarations hard to locate.
 #
@@ -107,9 +110,17 @@ set(package-contact "px4users@googlegroups.com")
 #
 
 list(APPEND CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake)
-
-include(px4_utils)
-include(px4_nuttx_utils)
+include(px4_${OS}_utils)
+set(px4_required_functions
+	px4_os_add_firmware
+	px4_os_prebuild_targets
+	px4_os_add_flags
+	)
+foreach(cmd ${px4_required_functions})
+	if(NOT COMMAND ${cmd})
+		message(FATAL_ERROR "cmake/px4_${OS}_utils.cmake must implement ${cmd}")
+	endif()
+endforeach()
 
 #=============================================================================
 # parameters
@@ -124,8 +135,8 @@ set_property(CACHE BOARD PROPERTY STRINGS px4fmu-v2 sitl)
 set(LABEL "simple" CACHE STRING "module set label")
 set_property(CACHE LABEL PROPERTY STRINGS simple default)
 
-set(NUTTX_BUILD_THREADS "4" CACHE STRING
-	"number of threads to use when building NuttX")
+set(THREADS "4" CACHE STRING
+	"number of threads to use for external build processes")
 
 set(required_toolchain_variables
 	CMAKE_C_COMPILER_ID
@@ -159,40 +170,25 @@ add_custom_target(submodule_clean
 #=============================================================================
 # external libraries
 #
-if(${OS} STREQUAL "nuttx")
-	px4_nuttx_add_export(OUT nuttx_export
-		CONFIG ${BOARD}
-		THREADS ${NUTTX_BUILD_THREADS}
-		DEPENDS git_nuttx)
-endif()
+px4_os_prebuild_targets(OUT prebuild_targets
+	BOARD ${BOARD}
+	THREADS ${THREADS})
 
 #=============================================================================
 # build flags
 #
-
-px4_add_common_flags(
+px4_os_add_flags(
+	BOARD ${BOARD}
 	C_FLAGS c_flags
 	CXX_FLAGS cxx_flags
 	EXE_LINKER_FLAGS exe_linker_flags
 	INCLUDE_DIRS include_dirs
 	LINK_DIRS link_dirs
 	DEFINITIONS definitions)
-
-if(${OS} STREQUAL "nuttx")
-	px4_add_nuttx_flags(
-		BOARD ${BOARD}
-		C_FLAGS c_flags
-		CXX_FLAGS cxx_flags
-		EXE_LINKER_FLAGS exe_linker_flags
-		INCLUDE_DIRS include_dirs
-		LINK_DIRS link_dirs
-		DEFINITIONS definitions)
-
-endif()
-
 px4_join(OUT CMAKE_EXE_LINKER_FLAGS LIST "${exe_linker_flags}" GLUE " ")
 px4_join(OUT CMAKE_C_FLAGS LIST "${c_flags}" GLUE " ")
 px4_join(OUT CMAKE_CXX_FLAGS LIST "${cxx_flags}" GLUE " ")
+
 include_directories(${include_dirs})
 link_directories(${link_dirs})
 add_definitions(${definitions})
diff --git a/cmake/px4_nuttx_utils.cmake b/cmake/px4_nuttx_utils.cmake
index 25f3cf0692..df10da85df 100644
--- a/cmake/px4_nuttx_utils.cmake
+++ b/cmake/px4_nuttx_utils.cmake
@@ -31,9 +31,28 @@
 #
 ############################################################################
 
+
+#=============================================================================
+#
+#	Defined functions in this file
+#
+# 	OS Specific Functions
+#
+#		* px4_nuttx_add_firmware
+#		* px4_nuttx_generate_builtin_commands
+#		* px4_nuttx_add_export
+#		* px4_nuttx_generate_romfs
+#
+# 	Required OS Inteface Functions
+#
+# 		* px4_os_add_flags
+#		* px4_os_prebuild_targets
+#
+
 include(px4_utils)
 
-#----------------------------------------------------------------------------
+#=============================================================================
+#
 #	px4_nuttx_add_firmware
 #
 #	This function adds a nuttx firmware target.
@@ -53,7 +72,6 @@ include(px4_utils)
 #	Example:
 #		px4_nuttx_add_firmware(TARGET fw_test EXE test)
 #
-#----------------------------------------------------------------------------
 function(px4_nuttx_add_firmware)
 	px4_parse_function_args(
 		NAME px4_nuttx_add_firmware
@@ -74,7 +92,8 @@ function(px4_nuttx_add_firmware)
 		)
 endfunction()
 
-#----------------------------------------------------------------------------
+#=============================================================================
+#
 #	px4_nuttx_generate_builtin_commands
 #
 #	This function generates the builtin_commands.c src for nuttx
@@ -91,9 +110,9 @@ endfunction()
 #		OUT	: generated builtin_commands.c src
 #
 #	Example:
-#		px4_nuttx_generate_builtin_commands(OUT <generated-src> MODULE_LIST px4_simple_app)
+#		px4_nuttx_generate_builtin_commands(
+#			OUT <generated-src> MODULE_LIST px4_simple_app)
 #
-#----------------------------------------------------------------------------
 function(px4_nuttx_generate_builtin_commands)
 	px4_parse_function_args(
 		NAME px4_nuttx_generate_builtin_commands
@@ -127,11 +146,12 @@ function(px4_nuttx_generate_builtin_commands)
 		${OUT})
 endfunction()
 
-#----------------------------------------------------------------------------
+#=============================================================================
+#
 #	px4_nuttx_add_export
 #
 #	This function generates a nuttx export.
-
+#
 #	Usage:
 #		px4_nuttx_add_export(
 #			OUT <out-target>
@@ -148,7 +168,6 @@ endfunction()
 #	Example:
 #		px4_nuttx_add_export(OUT nuttx_export CONFIG px4fmu-v2)
 #
-#----------------------------------------------------------------------------
 function(px4_nuttx_add_export)
 
 	px4_parse_function_args(
@@ -215,7 +234,8 @@ function(px4_nuttx_add_export)
 
 endfunction()
 
-#----------------------------------------------------------------------------
+#=============================================================================
+#
 #	px4_nuttx_generate_romfs
 #
 #	The functions generates the ROMFS filesystem for nuttx.
@@ -232,7 +252,6 @@ endfunction()
 #	Example:
 #		px4_nuttx_generate_romfs(OUT my_romfs ROOT "ROMFS/my_board")
 #
-#----------------------------------------------------------------------------
 function(px4_nuttx_generate_romfs)
 
 	px4_parse_function_args(
@@ -257,13 +276,14 @@ function(px4_nuttx_generate_romfs)
 
 endfunction()
 
-#----------------------------------------------------------------------------
-#	px4_add_nuttx_flags
+#=============================================================================
+#
+#	px4_add_flags
 #
 #	Set ths nuttx build flags.
 #
 #	Usage:
-#		px4_add_nuttx_flags(
+#		px4_add_flags(
 #			C_FLAGS <inout-variable>
 #			CXX_FLAGS <inout-variable>
 #			EXE_LINKER_FLAGS <inout-variable>
@@ -273,7 +293,7 @@ endfunction()
 #
 #	Input:
 #		BOARD					: flags depend on board/nuttx config
-
+#
 #	Input/Output: (appends to existing variable)
 #		C_FLAGS					: c compile flags variable
 #		CXX_FLAGS				: c++ compile flags variable
@@ -283,24 +303,32 @@ endfunction()
 #		DEFINITIONS				: definitions
 #
 #	Example:
-#		px4_add_nuttx_flags(
+#		px4_add_flags(
 #			C_FLAGS CMAKE_C_FLAGS
 #			CXX_FLAGS CMAKE_CXX_FLAGS
 #			EXE_LINKER_FLAG CMAKE_EXE_LINKER_FLAGS
 #			INCLUDES <list>)
 #
-#----------------------------------------------------------------------------
-function(px4_add_nuttx_flags)
+function(px4_add_flags)
 
 	set(inout_vars
 		C_FLAGS CXX_FLAGS EXE_LINKER_FLAGS INCLUDE_DIRS LINK_DIRS DEFINITIONS)
 
 	px4_parse_function_args(
-		NAME px4_add_nuttx_flags
+		NAME px4_add_flags
 		ONE_VALUE ${inout_vars} BOARD
 		REQUIRED ${inout_vars} BOARD
 		ARGN ${ARGN})
 
+	px4_add_common_flags(
+		BOARD ${BOARD}
+		C_FLAGS ${C_FLAGS}
+		CXX_FLAGS ${CXX_FLAGS}
+		EXE_LINKER_FLAGS ${EXE_LINKER_FLAGS}
+		INCLUDE_DIRS ${INCLUDE_DIRS}
+		LINK_DIRS ${LINK_DIRS}
+		DEFINITIONS ${DEFINITIONS})
+
 	set(nuttx_export_dir ${CMAKE_BINARY_DIR}/${BOARD}/NuttX/nuttx-export)
 	set(added_include_dirs
 		${nuttx_export_dir}/include
@@ -341,8 +369,44 @@ function(px4_add_nuttx_flags)
 	foreach(var ${inout_vars})
 		string(TOLOWER ${var} lower_var)
 		set(${${var}} ${${${var}}} ${added_${lower_var}} PARENT_SCOPE)
+		message(STATUS "nuttx: set(${${var}} ${${${var}}} ${added_${lower_var}} PARENT_SCOPE)")
 	endforeach()
 
 endfunction()
 
+#=============================================================================
+#
+#	px4_prebuild_targets
+#
+#	This function generates os dependent targets
+
+#	Usage:
+#		px4_os_prebuild_targets(
+#			OUT <out-list_of_targets>
+#			BOARD <in-string>
+#			)
+#
+#	Input:
+#		BOARD 		: board
+#		THREADS 	: number of threads for building
+#
+#	Output:
+#		OUT	: the target list
+#
+#	Example:
+#		px4_os_prebuild_targets(OUT target_list BOARD px4fmu-v2)
+#
+function(px4_prebuild_targets)
+	px4_parse_function_args(
+			NAME px4_add_os_libraries
+			ONE_VALUE OUT BOARD THREADS
+			REQUIRED OUT BOARD
+			ARGN ${ARGN})
+	px4_nuttx_add_export(OUT nuttx_export
+		CONFIG ${BOARD}
+		THREADS ${THREADS}
+		DEPENDS git_nuttx)
+	add_custom_target(${OUT} DEPENDS nuttx_export)
+endfunction()
+
 # vim: set noet fenc=utf-8 ff=unix nowrap:
diff --git a/cmake/px4_utils.cmake b/cmake/px4_utils.cmake
index 3d3b5563e8..5333c454a8 100644
--- a/cmake/px4_utils.cmake
+++ b/cmake/px4_utils.cmake
@@ -31,9 +31,26 @@
 #
 ############################################################################
 
+#=============================================================================
+#
+#	Defined functions in this file
+#
+# 	utility functions
+#
+#		* px4_parse_function_args
+#		* px4_add_git_submodule
+#		* px4_prepend_string
+#		* px4_join
+#		* px4_add_module
+#		* px4_generate_messages
+#		* px4_add_upload
+#		* px4_add_common_flags
+#
+
 include(CMakeParseArguments)
 
-#----------------------------------------------------------------------------
+#=============================================================================
+#
 #	px4_parse_function_args
 #
 #	This function simpliies usage of the cmake_parse_arguments module.
@@ -78,7 +95,6 @@ include(CMakeParseArguments)
 #			name: hello
 #			list: a b c
 #
-#----------------------------------------------------------------------------
 function(px4_parse_function_args)
 	cmake_parse_arguments(IN "" "NAME" "OPTIONS;ONE_VALUE;MULTI_VALUE;REQUIRED;ARGN" "${ARGN}")
 	cmake_parse_arguments(OUT "${IN_OPTIONS}" "${IN_ONE_VALUE}" "${IN_MULTI_VALUE}" "${IN_ARGN}")
@@ -95,13 +111,14 @@ function(px4_parse_function_args)
 	endforeach()
 endfunction()
 
-#----------------------------------------------------------------------------
-#	add_git_submodule
+#=============================================================================
+#
+#	px4_add_git_submodule
 #
 #	This function add a git submodule target.
 #
 #	Usage:
-#		add_git_submodule(TARGET <target> PATH <path>)
+#		px4_add_git_submodule(TARGET <target> PATH <path>)
 #
 #	Input:
 #		PATH		: git submodule path
@@ -110,9 +127,8 @@ endfunction()
 #		TARGET		: git target
 #
 #	Example:
-#		add_git_submodule(TARGET git_nuttx PATH "NuttX")
+#		px4_add_git_submodule(TARGET git_nuttx PATH "NuttX")
 #
-#----------------------------------------------------------------------------
 function(px4_add_git_submodule)
 	px4_parse_function_args(
 		NAME px4_add_git_submodule
@@ -131,7 +147,8 @@ function(px4_add_git_submodule)
 	)
 endfunction()
 
-#----------------------------------------------------------------------------
+#=============================================================================
+#
 #	px4_prepend_string
 #
 #	This function prepends a string to a list
@@ -152,7 +169,6 @@ endfunction()
 #			path/to/src/file1.cpp
 #			path/to/src/file2.cpp
 #
-#----------------------------------------------------------------------------
 function(px4_prepend_string)
 	px4_parse_function_args(
 		NAME px4_prepend_string
@@ -167,7 +183,8 @@ function(px4_prepend_string)
 	set(${OUT} ${${OUT}} PARENT_SCOPE)
 endfunction()
 
-#----------------------------------------------------------------------------
+#=============================================================================
+#
 #	px4_join
 #
 #	This function joins a list with a given separator. If list is not
@@ -188,7 +205,6 @@ endfunction()
 #		test_join would then be:
 #			"a;b;c"
 #
-#----------------------------------------------------------------------------
 function(px4_join)
 	px4_parse_function_args(
 		NAME px4_join
@@ -200,7 +216,8 @@ function(px4_join)
 	set(${OUT} ${_TMP_STR} PARENT_SCOPE)
 endfunction()
 
-#----------------------------------------------------------------------------
+#=============================================================================
+#
 #	px4_add_module
 #
 #	This function builds a static library from a module description.
@@ -236,7 +253,6 @@ endfunction()
 #				git_nuttx
 #			)
 #
-#----------------------------------------------------------------------------
 function(px4_add_module)
 	px4_parse_function_args(
 		NAME px4_add_module
@@ -264,11 +280,12 @@ function(px4_add_module)
 	set_target_properties(${MODULE} PROPERTIES LINK_INTERFACE_MULTIPLICITY 4)
 endfunction()
 
-#----------------------------------------------------------------------------
+#=============================================================================
+#
 #	px4_generate_messages
 #
 #	This function generates source code from ROS msg definitions.
-
+#
 #	Usage:
 #		px4_generate_messages(TARGET <target> MSGS <msg-files>)
 #
@@ -286,7 +303,6 @@ endfunction()
 #			[ DEPENDS <dependencies> ]
 #			)
 #
-#----------------------------------------------------------------------------
 function(px4_generate_messages)
 	px4_parse_function_args(
 		NAME px4_generate_messages
@@ -349,11 +365,12 @@ function(px4_generate_messages)
 		DEPENDS ${msg_multi_files_out} ${msg_files_out})
 endfunction()
 
-#----------------------------------------------------------------------------
+#=============================================================================
+#
 #	px4_add_upload
 #
 #	This function generates source code from ROS msg definitions.
-
+#
 #	Usage:
 #		px4_add_upload(OUT <target> BUNDLE <file.px4>)
 #
@@ -370,7 +387,6 @@ endfunction()
 #			BUNDLE main.px4
 #			)
 #
-#----------------------------------------------------------------------------
 function(px4_add_upload)
 	px4_parse_function_args(
 		NAME px4_generate_messages
@@ -403,13 +419,15 @@ function(px4_add_upload)
 		)
 endfunction()
 
-#----------------------------------------------------------------------------
+#=============================================================================
+#
 #	px4_add_common_flags
 #
 #	Set ths default build flags.
 #
 #	Usage:
 #		px4_add_common_flags(
+#			BOARD <in-string>
 #			C_FLAGS <inout-variable>
 #			CXX_FLAGS <inout-variable>
 #			EXE_LINKER_FLAGS <inout-variable>
@@ -417,6 +435,9 @@ endfunction()
 #			LINK_DIRS <inout-variable>
 #			DEFINITIONS <inout-variable>)
 #
+#	Input:
+#		BOARD					: board
+#
 #	Input/Output: (appends to existing variable)
 #		C_FLAGS					: c compile flags variable
 #		CXX_FLAGS				: c++ compile flags variable
@@ -427,12 +448,12 @@ endfunction()
 #
 #	Example:
 #		px4_add_common_flags(
+#			BOARD px4fmu-v2
 #			C_FLAGS CMAKE_C_FLAGS
 #			CXX_FLAGS CMAKE_CXX_FLAGS
 #			EXE_LINKER_FLAG CMAKE_EXE_LINKER_FLAGS
 #			INCLUDES <list>)
 #
-#----------------------------------------------------------------------------
 function(px4_add_common_flags)
 
 	set(inout_vars
@@ -440,8 +461,8 @@ function(px4_add_common_flags)
 
 	px4_parse_function_args(
 		NAME px4_add_common_flags
-		ONE_VALUE ${inout_vars}
-		REQUIRED ${inout_vars}
+		ONE_VALUE ${inout_vars} BOARD
+		REQUIRED ${inout_vars} BOARD
 		ARGN ${ARGN})
 
 	set(warnings
@@ -569,8 +590,10 @@ function(px4_add_common_flags)
 
 	set(added_link_dirs) # none used currently
 
+	string(TOUPPER ${BOARD} board_upper)
+	string(REPLACE "-" "_" board_config ${board_upper})
 	set(added_definitions
-		-DCONFIG_ARCH_BOARD_${BOARD_CONFIG}
+		-DCONFIG_ARCH_BOARD_${board_config}
 		)
 
 	set(added_exe_link_flags
@@ -582,13 +605,9 @@ function(px4_add_common_flags)
 	foreach(var ${inout_vars})
 		string(TOLOWER ${var} lower_var)
 		set(${${var}} ${${${var}}} ${added_${lower_var}} PARENT_SCOPE)
+		message(STATUS "set(${${var}} ${${${var}}} ${added_${lower_var}} PARENT_SCOPE)")
 	endforeach()
 
 endfunction()
 
-
-
-
-
-
 # vim: set noet fenc=utf-8 ff=unix nowrap:
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index d2a80d939f..6584e136cb 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -64,7 +64,7 @@ if (${OS} STREQUAL "nuttx")
 	px4_nuttx_add_firmware(OUT fw_main.px4 EXE main)
 	px4_add_upload(OUT upload OS ${OS} BOARD ${BOARD} BUNDLE fw_main.px4)
 
-	px4_nuttx_generate_romfs(OUT romfs.img ROOT ROMFS/px4fmu_common)
+	px4_generate_romfs(OUT romfs.img ROOT ROMFS/px4fmu_common)
 
 endif()
 
diff --git a/src/platforms/common/CMakeLists.txt b/src/platforms/common/CMakeLists.txt
index 0bc74e228a..7d486c9709 100644
--- a/src/platforms/common/CMakeLists.txt
+++ b/src/platforms/common/CMakeLists.txt
@@ -33,10 +33,9 @@
 set(depends
 	msg_gen
 	)
-if(${OS} STREQUAL "nuttx")
-	list(APPEND depends
-		nuttx_export
-		)
+
+if (prebuild_targets)
+	list(APPEND depends prebuild_targets)
 endif()
 
 px4_add_module(