diff --git a/sw/tools/Makefile b/sw/tools/Makefile
index 6358d55550..e0f0b33ccf 100644
--- a/sw/tools/Makefile
+++ b/sw/tools/Makefile
@@ -24,7 +24,7 @@ Q=@
 
 OCAML=ocaml
 OCAMLC=ocamlc
-INCLUDES=-I ../lib/ocaml $(shell ocamlfind query -r -i-format xml-light)
+INCLUDES=-I ../lib/ocaml $(shell ocamlfind query -r -i-format xml-light) -I .
 OCAMLNETINCLUDES=$(shell ocamlfind query -r -i-format netstring)
 OCAMLNETCMA=$(shell ocamlfind query -r -a-format -predicates byte netstring)
 OCAMLLEX=ocamllex
@@ -42,13 +42,13 @@ gen_flight_plan.out : $(FP_CMO) ../lib/ocaml/lib-pprz.cma
 fp_proc.cmo : fp_proc.cmi
 gen_flight_plan.cmo : fp_proc.cmi
 
+gen_common.cmo : gen_common.cmi
 
-
-%.out : %.ml Makefile
+%.out : %.ml gen_common.ml Makefile
 	@echo OC $<
 	$(Q)$(OCAMLC) $(INCLUDES) -o $@ unix.cma str.cma ivy-ocaml.cma xml-light.cma lib-pprz.cma gen_common.cmo $<
 	@cat ../../pprz_src_test.sh > $@
-	@echo '$(OCAML) $(shell ocamlfind query -r -i-format xml-light) $(OCAMLNETINCLUDES) -I $$PAPARAZZI_SRC/sw/lib/ocaml unix.cma str.cma ivy-ocaml.cma xml-light.cma $(OCAMLNETCMA) lib-pprz.cma $$PAPARAZZI_BIN/$< $$*' >> $@
+	@echo '$(OCAML) -I $$PAPARAZZI_SRC/sw/tools $(shell ocamlfind query -r -i-format xml-light) $(OCAMLNETINCLUDES) -I $$PAPARAZZI_SRC/sw/lib/ocaml unix.cma str.cma ivy-ocaml.cma xml-light.cma $(OCAMLNETCMA) lib-pprz.cma gen_common.cmo $$PAPARAZZI_BIN/$< $$*' >> $@
 	@chmod a+x $@
 
 %.cmo : %.ml ../lib/ocaml/lib-pprz.cma
diff --git a/sw/tools/gen_aircraft.ml b/sw/tools/gen_aircraft.ml
index f748a160a6..cc5130f8e5 100644
--- a/sw/tools/gen_aircraft.ml
+++ b/sw/tools/gen_aircraft.ml
@@ -26,7 +26,8 @@
 
 open Printf
 module U = Unix
-module GC = Gen_common
+
+open Gen_common
 
 let (//) = Filename.concat
 
@@ -62,9 +63,9 @@ let check_unique_id_and_name = fun conf ->
 (** [get_modules dir xml]
  * [dir] is the conf directory for modules, [xml] is the parsed airframe.xml *)
 let get_modules = fun dir xml ->
-  let modules = GC.get_modules_of_airframe xml in
+  let modules = Gen_common.get_modules_of_airframe xml in
   (* build a list (file name, (xml, xml list of flags)) *)
-  let extract = List.map GC.get_full_module_conf modules in
+  let extract = List.map Gen_common.get_full_module_conf modules in
   (* return a list of name and a list of pairs (xml, xml list) *)
   List.split extract
 
@@ -75,14 +76,14 @@ let get_modules = fun dir xml ->
  **)
 let dump_module_section = fun xml f ->
   (* get modules *)
-  let (files, modules) = get_modules GC.modules_dir xml in
+  let (files, modules) = get_modules Gen_common.modules_dir xml in
   (* print modules directories and includes for all targets *)
   fprintf f "\n####################################################\n";
   fprintf f   "# modules makefile section\n";
   fprintf f   "####################################################\n";
   fprintf f "\n# include modules directory for all targets\n";
   (* get dir and target list *)
-  let dir_list = GC.get_modules_dir modules in
+  let dir_list = Gen_common.get_modules_dir modules in
 (**
   let target_list = union_of_lists (List.map (fun (m,_) -> get_targets_of_module m) modules) in
   List.iter (fun target -> fprintf f "%s.CFLAGS += -I modules -I arch/$(ARCH)/modules\n" target) target_list;
@@ -96,7 +97,7 @@ let dump_module_section = fun xml f ->
     let dir = try Xml.attrib m "dir" with _ -> name in
     let dir_name = (String.uppercase dir)^"_DIR" in
     (* get the list of all the targets for this module *)
-    let module_target_list = GC.get_targets_of_module m in
+    let module_target_list = Gen_common.get_targets_of_module m in
     (* print global flags as compilation defines and flags *)
     fprintf f "\n# makefile for module %s in modules/%s\n" name dir;
     List.iter (fun flag ->
@@ -116,7 +117,7 @@ let dump_module_section = fun xml f ->
     (* Look for makefile section *)
     List.iter (fun l ->
       if ExtXml.tag_is l "makefile" then begin
-        let targets = GC.targets_of_field l in
+        let targets = Gen_common.targets_of_field l in
         (* Look for defines, flags, files, ... *)
         List.iter (fun field ->
           match String.lowercase (Xml.tag field) with
diff --git a/sw/tools/gen_common.mli b/sw/tools/gen_common.mli
new file mode 100644
index 0000000000..9ec2fc7774
--- /dev/null
+++ b/sw/tools/gen_common.mli
@@ -0,0 +1,64 @@
+(*
+ * $Id$
+ *
+ * generic tools for modules
+ *
+ * Copyright (C) 2010 Gautier Hattenberger
+ *
+ * This file is part of paparazzi.
+ *
+ * paparazzi is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * paparazzi is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with paparazzi; see the file COPYING.  If not, write to
+ * the Free Software Foundation, 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ *
+ *)
+
+val modules_dir : string
+
+(** remove all duplicated elements of a list *)
+val singletonize : 'a list -> 'a list
+
+(** [get_modules_of_airframe xml]
+ * Returns a list of modules ("load" node) from airframe file *)
+val get_modules_of_airframe : Xml.xml -> Xml.xml list
+
+(** [get_full_module_conf module] Parse module configuration file
+ * Returns module file name and a pair (xml, xml list): parsed file, children *)
+val get_full_module_conf : Xml.xml -> (string * (Xml.xml * Xml.xml list))
+
+(** [get_module_conf module] Parse module configuration file
+ * Returns parsed xml file *)
+val get_module_conf : Xml.xml -> Xml.xml
+
+(** [get_targets_of_module xml] Returns the list of targets of a module *)
+val get_targets_of_module : Xml.xml -> string list
+
+(** [unload_unused_modules modules ?print_error]
+ * Returns a list of [modules] where unused modules are removed
+ * If [print_error] is true, a warning is printed *)
+val unload_unused_modules : Xml.xml list -> bool -> Xml.xml list
+
+(** [get_modules_name xml]
+ * Returns a list of loaded modules' name *)
+val get_modules_name : Xml.xml -> string list
+
+(** [targets_of_field]
+ * Returns the targets of a makefile node in modules
+ * Default "ap|sim" *)
+val targets_of_field : Xml.xml -> string list
+
+(** [get_modules_dir xml]
+ * Returns the list of modules directories *)
+val get_modules_dir : (Xml.xml * 'a) list -> string list
+