diff --git a/ArduPlane/CMakeLists.txt b/ArduPlane/CMakeLists.txt
index 9757f3369c..061888e067 100644
--- a/ArduPlane/CMakeLists.txt
+++ b/ArduPlane/CMakeLists.txt
@@ -16,10 +16,12 @@ include(CMakeParseArguments)
 include(APMOption)
 
 # options
-add_definitions(-DUSE_CMAKE_APM_CONFIG)
 include(options.cmake)
 include_directories(${CMAKE_BINARY_DIR})
-apm_option_generate_config(FILE "APM_Config_cmake.h" OPTIONS ${APM_OPTIONS})
+add_definitions(-DUSE_CMAKE_APM_CONFIG)
+apm_option_generate_config(FILE "APM_Config_cmake.h" BUILD_FLAGS APM_BUILD_FLAGS)
+add_definitions(${APM_BUILD_FLAGS})
+message(STATUS "build flags: ${APM_BUILD_FLAGS}")
 #configure_file(APM_Config2.h.cmake APM_Config2.h)
 
 # disallow in-source build
@@ -42,6 +44,7 @@ set(ARDUINO_EXTRA_LIBRARIES_PATH ${CMAKE_SOURCE_DIR}/../libraries)
 set(${FIRMWARE_NAME}_SKETCH ${CMAKE_SOURCE_DIR}/../${PROJECT_NAME})
 set(${FIRMWARE_NAME}_BOARD ${APM_PROCESSOR})
 set(${FIRMWARE_NAME}_PORT ${APM_PROGRAMMING_PORT})
+set(${FIRMWARE_NAME}_SRCS ${CMAKE_BINARY_DIR}/APM_Config_cmake.h)
 generate_arduino_firmware(${FIRMWARE_NAME})
 install(FILES ${CMAKE_BINARY_DIR}/${FIRMWARE_NAME}.hex DESTINATION "/")
 
diff --git a/ArduPlane/options.cmake b/ArduPlane/options.cmake
index 9f324202d9..f984b36aba 100644
--- a/ArduPlane/options.cmake
+++ b/ArduPlane/options.cmake
@@ -97,7 +97,7 @@ apm_option("MAV_SYSTEM_ID" TYPE STRING ADVANCED
     DESCRIPTION "MAVLink System ID?"
     DEFAULT "1")
 
-apm_option("MAVLINKV10" TYPE BOOL DEFINE_ONLY
+apm_option("MAVLINK10" TYPE BOOL DEFINE_ONLY BUILD_FLAG
     DESCRIPTION "Use mavlink version 1.0?" 
     DEFAULT OFF)
 
diff --git a/cmake/modules/APMOption.cmake b/cmake/modules/APMOption.cmake
index 48bb054dab..6114ff44aa 100644
--- a/cmake/modules/APMOption.cmake
+++ b/cmake/modules/APMOption.cmake
@@ -1,6 +1,26 @@
+# apm_option: options parsing for ardupilotmega
+#
+# OPTIONS:
+#   ADVANCED - indicates this option is advaned (hidden in gui unless advanced selected)
+#   DEFINE_ONLY - this flag is either indicates that the variable is defined if true, and not defined if false
+#   BUILD_FLAG - this flag forces the variable to be added to build flags, for files that
+#       don't include the config header
+#
+# SINGLE INPUT ARGUMENTS: (can only pass one arguments)
+#   TYPE - the type of the argument (BOOL for on/off variables/ STRING for all others)
+#   DESCRIPTION - description of option, shown as tool-tip and written in config file
+#   DEFAULT - the default value of the option
+#
+# MULTIPLE VARIABLE ARGUMENTS: (can pass a lit of items)
+#   OPTIONS - values that this option may take, if only a finite set is possible, creates combo-box in gui 
+#   DEPENDS - a list of booleans that this argument depends on, can be used to disable options when the
+#       are not appropriate
+#
+# Author: James Goppert
+#
 function(apm_option NAME)
     cmake_parse_arguments(ARG
-        "ADVANCED;DEFINE_ONLY"
+        "ADVANCED;DEFINE_ONLY;BUILD_FLAG"
         "TYPE;DESCRIPTION;DEFAULT" "OPTIONS;DEPENDS" ${ARGN})
 
     #message(STATUS "parsing argument: ${NAME}")
@@ -21,18 +41,30 @@ function(apm_option NAME)
     # force variable reinit if it was internal (hidden)
     get_property(VAR_TYPE CACHE ${NAME} PROPERTY TYPE) 
     if ("${VAR_TYPE}" STREQUAL "INTERNAL")
-        message(STATUS "\tVAR_TYPE: ${VAR_TYPE}")
+        #message(STATUS "\tVAR_TYPE: ${VAR_TYPE}")
         set("${NAME}" "${ARG_DEFAULT}" CACHE "${ARG_TYPE}" "${ARG_DESCRIPTION}" FORCE) 
 
-    # if not hidden, add it to the global options list
-    else() 
-        set(APM_OPTIONS ${APM_OPTIONS} ${NAME} CACHE INTERNAL "list of all options")
-        list(REMOVE_DUPLICATES APM_OPTIONS)
-        #message(STATUS "APM_OPTIONS: ${APM_OPTIONS}")
+    # if a build flag, initialize it and add it to the global options list
+    elseif(${ARG_BUILD_FLAG}) 
+        #message(STATUS "build flag found for item ${NAME}")
+        set(APM_BUILD_FLAGS_LIST ${APM_BUILD_FLAGS_LIST} ${NAME} CACHE INTERNAL "list of all build flags")
+        list(REMOVE_DUPLICATES APM_BUILD_FLAGS_LIST)
+
+    # if not hidden, and not a build flag, add it to the global options list
+    else()
+        set(APM_OPTIONS_LIST ${APM_OPTIONS_LIST} ${NAME} CACHE INTERNAL "list of all options")
+        list(REMOVE_DUPLICATES APM_OPTIONS_LIST)
+
     endif()
 
-    # set options for combo box
-    set_property(CACHE "${NAME}" PROPERTY STRINGS ${ARG_OPTIONS})
+    # set list of options
+    if (NOT "${ARG_OPTIONS}" STREQUAL "")
+        set_property(CACHE "${NAME}" PROPERTY STRINGS ${ARG_OPTIONS})
+        list(FIND ARG_OPTIONS "${ARG_DEFAULT}" ARG_POSITION)
+        if (ARG_POSITION EQUAL -1)
+            message(FATAL_ERROR "default value: ${ARG_DEFAULT} not in given set of options: ${ARG_OPTIONS}")
+        endif()
+    endif()
 
     # mark as advanced if advanced option given
     if(ARG_ADVANCED)
@@ -47,17 +79,27 @@ function(apm_option NAME)
 
 endfunction()
 
+# apm_option_generate_config: generates a config file using the list of options.
+#
+# SINGLE INPUT ARGUMENTS: (can only pass one arguments)
+#   FILE - the file to write the config to
+#   BUILD_FLAGS - variable to store build flags in
+#
+# Author: James Goppert
+#
 function(apm_option_generate_config)
-    cmake_parse_arguments(ARG "" "FILE" "" ${ARGN})
-    list(REMOVE_DUPLICATES APM_OPTIONS)
+    cmake_parse_arguments(ARG "" "FILE;BUILD_FLAGS" "" ${ARGN})
+
+    # options
+    list(REMOVE_DUPLICATES APM_OPTIONS_LIST)
     file (WRITE "${CMAKE_BINARY_DIR}/${ARG_FILE}" "//automatically generated, do not edit\n")
     file (APPEND "${CMAKE_BINARY_DIR}/${ARG_FILE}" "#define OFF 0\n#define ON 1\n")
-    foreach(ITEM ${APM_OPTIONS})
-        #message(STATUS "item: ${ITEM}")
+    foreach(ITEM ${APM_OPTIONS_LIST})
+        #message(STATUS "option: ${ITEM}")
         get_property(ITEM_VALUE CACHE ${ITEM} PROPERTY VALUE) 
         get_property(ITEM_HELP CACHE ${ITEM} PROPERTY HELPSTRING) 
-        if (${ITEM}_DEFINE_ONLY)
-            if (${ITEM}_VALUE)
+        if (${${ITEM}_DEFINE_ONLY})
+            if (${ITEM_VALUE})
                 file(APPEND "${CMAKE_BINARY_DIR}/${ARG_FILE}" "\n#define ${ITEM} // ${ITEM_HELP}")
             else()
                 file(APPEND "${CMAKE_BINARY_DIR}/${ARG_FILE}" "\n//#define ${ITEM} // ${ITEM_HELP}")
@@ -66,4 +108,19 @@ function(apm_option_generate_config)
             file(APPEND "${CMAKE_BINARY_DIR}/${ARG_FILE}" "\n#define ${ITEM} ${ITEM_VALUE} // ${ITEM_HELP}")
         endif()
     endforeach()
+
+    # build flags
+    list(REMOVE_DUPLICATES APM_BUILD_FLAGS_LIST)
+    foreach(ITEM ${APM_BUILD_FLAGS_LIST})
+        #message(STATUS "build flags: ${ITEM}")
+        get_property(ITEM_VALUE CACHE ${ITEM} PROPERTY VALUE) 
+        if (${${ITEM}_DEFINE_ONLY})
+            if (${ITEM_VALUE})
+                set(${ARG_BUILD_FLAGS} ${${ARG_BUILD_FLAGS}} "-D${ITEM}" CACHE INTERNAL "build flags")
+            endif()
+        else()
+            set(${ARG_BUILD_FLAGS} ${${ARG_BUILD_FLAGS}} "-D${ITEM}=${ITEM_VALUE}" CACHE INTERNAL "build flags")
+        endif()
+    endforeach()
+
 endfunction()