diff --git a/libraries/AP_HAL/AP_HAL.h b/libraries/AP_HAL/AP_HAL.h
index aed2715e19..4322098fd7 100644
--- a/libraries/AP_HAL/AP_HAL.h
+++ b/libraries/AP_HAL/AP_HAL.h
@@ -3,6 +3,7 @@
 #define __AP_HAL_H__
 
 #include "AP_HAL_Namespace.h"
+#include "AP_HAL_Boards.h"
 
 /* HAL Module Classes (all pure virtual) */
 #include "UARTDriver.h"
diff --git a/libraries/AP_HAL/AP_HAL_Boards.h b/libraries/AP_HAL/AP_HAL_Boards.h
new file mode 100644
index 0000000000..01d9072b6f
--- /dev/null
+++ b/libraries/AP_HAL/AP_HAL_Boards.h
@@ -0,0 +1,18 @@
+
+#ifndef __AP_HAL_BOARDS_H__
+#define __AP_HAL_BOARDS_H__
+
+/**
+ * C preprocesor enumeration of the boards supported by the AP_HAL.
+ * This list exists so HAL_BOARD == HAL_BOARD_xxx preprocessor blocks
+ * can be used to exclude HAL boards from the build when appropriate.
+ * Its not an elegant solution but we cant get too fancy if we want to
+ * work with the Arduino mk and IDE builds without too much modification.
+ */
+ 
+#define HAL_BOARD_APM1     1
+#define HAL_BOARD_APM2     2
+#define HAL_BOARD_AVR_SITL 3
+
+#endif // __AP_HAL_BOARDS_H__
+