diff --git a/conf/modules/telemetry_transparent.xml b/conf/modules/telemetry_transparent.xml
index ead5dac72c..4347f63d4a 100644
--- a/conf/modules/telemetry_transparent.xml
+++ b/conf/modules/telemetry_transparent.xml
@@ -11,7 +11,7 @@
     <configure name="MODEM_BAUD" value="B57600" description="UART baud rate"/>
   </doc>
   <header/>
-  <makefile target="ap">
+  <makefile target="!fbw|sim|nps">
     <configure name="MODEM_PORT" case="upper|lower"/>
     <define name="USE_$(MODEM_PORT_UPPER)"/>
     <define name="$(MODEM_PORT_UPPER)_BAUD" value="$(MODEM_BAUD)"/>
diff --git a/sw/lib/ocaml/gen_common.ml b/sw/lib/ocaml/gen_common.ml
index 318af5bc97..44cfba2378 100644
--- a/sw/lib/ocaml/gen_common.ml
+++ b/sw/lib/ocaml/gen_common.ml
@@ -24,6 +24,31 @@
 
 open Printf
 
+(** simple boolean expressions *)
+type bool_expr =
+  | Var of string
+  | Not of bool_expr
+  | And of bool_expr * bool_expr
+  | Or of bool_expr * bool_expr
+
+(** evaluate a boolean expression for a given value *)
+let rec eval_bool v = function
+  | Var x -> v = x
+  | Not e -> not (eval_bool v e)
+  | And (e1, e2) -> eval_bool v e1 && eval_bool v e2
+  | Or (e1, e2) -> eval_bool v e1 || eval_bool v e2
+
+(** pretty print boolean expression *)
+let print_bool = fun v e ->
+  let rec print_b v = function
+    | Var x -> eprintf "Var ( %s =? %s ) " x v
+    | Not e -> eprintf "Not ( "; (print_b v e); eprintf ") "
+    | And (e1, e2) -> eprintf "And ( "; print_b v e1; print_b v e2; eprintf ") "
+    | Or (e1, e2) -> eprintf "Or ( "; print_b v e1; print_b v e2; eprintf ") "
+  in
+  print_b v e; eprintf "\n"
+
+
 type module_conf = {
     name: string;
     xml: Xml.xml;
@@ -31,7 +56,7 @@ type module_conf = {
     filename: string;
     vpath: string option;(* this field should be removed after transition phase *)
     param: Xml.xml list;
-    targets: string list
+    targets: bool_expr
   }
 
 let (//) = Filename.concat
@@ -55,12 +80,21 @@ let union = fun l1 l2 -> singletonize (l1 @ l2)
 let union_of_lists = fun l -> singletonize (List.flatten l)
 
 (** [targets_of_field]
-    * Returns the targets of a makefile node in modules
-    * Default "ap|sim" *)
+ * Returns the targets expression of a makefile node in modules
+ * Default "ap|sim" *)
 let targets_of_field =
+  let rec expr_of_targets op = function
+    | [] -> Var ""
+    | [e] -> Var e
+    | l::ls -> op (Var l) (expr_of_targets op ls)
+  in
   let pipe = Str.regexp "|" in
   fun field default ->
-    Str.split pipe (ExtXml.attrib_or_default field "target" default)
+    let f = ExtXml.attrib_or_default field "target" default in
+    if String.length f > 0 && String.get f 0 = '!' then
+      Not (expr_of_targets (fun x y -> Or(x,y)) (Str.split pipe (String.sub f 1 ((String.length f) - 1))))
+    else
+      expr_of_targets (fun x y -> Or(x,y)) (Str.split pipe f)
 
 (** [get_autopilot_of_airframe xml]
     * Returns (autopilot xml, main freq) from airframe xml file *)
@@ -77,15 +111,14 @@ let get_autopilot_of_airframe = fun xml ->
     | _ -> failwith "Error: you have more than one 'autopilot' section in your airframe file"
 
 (** [get_targets_of_module xml]
-    * Returns the list of targets of a module *)
+ * Returns the boolean expression of targets of a module *)
 let get_targets_of_module = fun xml ->
-  let targets = Xml.map
-      (fun x ->
-        match String.lowercase (Xml.tag x) with
-        | "makefile" -> targets_of_field x Env.default_module_targets
-        | _ -> []
-      ) xml in
-  singletonize (List.flatten targets)
+  Xml.fold (fun a x ->
+    match String.lowercase (Xml.tag x) with
+    | "makefile" when a = Var "" -> targets_of_field x Env.default_module_targets
+    | "makefile" -> Or (a, targets_of_field x Env.default_module_targets)
+    | _ -> a
+  ) (Var "") xml
 
 let module_name = fun xml ->
   let name = ExtXml.attrib xml "name" in
@@ -103,7 +136,7 @@ let get_module = fun m global_targets ->
       if not (Sys.file_exists file) then raise (Subsystem file) else
       let xml = ExtXml.parse_file file in
       let targets = get_targets_of_module xml in
-      let targets = union global_targets targets in
+      let targets = Or (global_targets, targets) in
       { name = name; xml = xml; file = file; filename = filename; vpath = None;
         param = Xml.children m; targets = targets }
   | "load" -> (* this case should be removed after transition phase *)
@@ -120,8 +153,8 @@ let get_module = fun m global_targets ->
       let file = dir // filename in
       let xml = ExtXml.parse_file file in
       let targets = get_targets_of_module xml in
-      let extra_targets = global_targets @ targets_of_field m "" in
-      let targets = singletonize (extra_targets @ targets) in
+      let extra_targets = Or (global_targets, targets_of_field m "") in
+      let targets = Or (extra_targets, targets) in
       { name = name; xml = xml; file = file; filename = filename; vpath = vpath;
         param = Xml.children m; targets = targets }
   | _ -> Xml2h.xml_error "module or load"
@@ -130,28 +163,31 @@ let get_module = fun m global_targets ->
  * Test if [target] is allowed [targets]
  * Return true if target is allowed, false if target is not in list or rejected (prefixed by !) *)
 let test_targets = fun target targets ->
-  (* test for inverted selection
-   * FIXME: only the first target should have the invert sign ('!')
-   *)
-  let inv =
-    try
-      let hd = List.hd targets in
-      if String.get hd 0 = '!' then not
-      else (fun x -> x)
-    with _ -> (fun x -> x)
-  in
-  (* return inverted result if needed *)
-  inv (List.exists (fun t ->
-    let l = String.length t in
-    (* remove first char if invert sign *)
-    let t = if l > 0 && t.[0] = '!' then String.sub t 1 (l-1) else t in
-    t = target
-  ) targets)
+  eval_bool target targets
 
+exception Firmware_Found of string
 (** [get_modules_of_airframe xml]
  * Returns a list of module configuration from airframe file *)
 let rec get_modules_of_airframe = fun ?target xml ->
   let is_module = fun tag -> List.mem tag [ "module"; "load" ] in
+  (* first, find firmware related to the target *)
+  let firmware =
+    match target with
+    | None -> None
+    | Some t -> begin try
+        Xml.iter (fun x ->
+          if Xml.tag x = "firmware" then begin
+            let name = ExtXml.attrib x "name" in
+            Xml.iter (fun x ->
+              if Xml.tag x = "target" then begin
+                if Xml.attrib x "name" = t then raise (Firmware_Found name)
+              end) x
+          end) xml;
+          None
+        with Firmware_Found f -> Some f | _ -> None
+    end
+  in
+  (* extract modules from xml tree *)
   let rec iter_modules = fun targets modules xml ->
     match xml with
     | Xml.PCData _ -> modules
@@ -162,6 +198,16 @@ let rec get_modules_of_airframe = fun ?target xml ->
             (fun acc xml -> iter_modules targets acc xml)
             (m :: modules) children
         with Subsystem _file -> modules end
+    | Xml.Element (tag, _attrs, children) when tag = "firmware" ->
+        let name = Xml.attrib xml "name" in
+        begin match firmware with
+        | Some f when f = name ->
+            List.fold_left (fun acc xml ->
+              iter_modules targets acc xml) modules children
+        | None ->
+            List.fold_left (fun acc xml ->
+              iter_modules targets acc xml) modules children
+        | _ -> modules end (* skip wrong firmware *)
     | Xml.Element (tag, _attrs, children) when tag = "target" ->
         let target_name = Xml.attrib xml "name" in
         begin match target with
@@ -177,11 +223,11 @@ let rec get_modules_of_airframe = fun ?target xml ->
           if tag = "modules" then targets_of_field xml "" else targets in
         List.fold_left
           (fun acc xml -> iter_modules targets acc xml) modules children in
-  let modules = iter_modules [] [] xml in
+  let modules = iter_modules (Var "") [] xml in
   let ap_modules =
     try
       let ap_file = fst (get_autopilot_of_airframe xml) in
-      iter_modules [] [] (ExtXml.parse_file ap_file)
+      iter_modules (Var "") [] (ExtXml.parse_file ap_file)
     with _ -> [] in
   let modules = List.rev (ap_modules @ modules) in
   match target with
@@ -205,7 +251,7 @@ let get_modules_of_flight_plan = fun xml ->
     | Xml.Element (tag, _attrs, children) ->
         List.fold_left
           (fun acc xml -> iter_modules targets acc xml) modules children in
-  List.rev (iter_modules [] [] xml)
+  List.rev (iter_modules (Var "") [] xml)
 
 (** [singletonize_modules xml]
  * Returns a list of singletonized modules were options are merged
@@ -232,7 +278,11 @@ let singletonize_modules = fun ?(verbose=false) ?target xml ->
         end;
         let m = { name = x.name; xml = x.xml; file = x.file; filename = x.filename;
         vpath = x.vpath; param = List.flatten (List.map (fun m -> m.param) ([x] @ duplicates));
-        targets = singletonize (List.flatten (List.map (fun m -> m.targets) ([x] @ duplicates))) } in
+        targets = List.fold_left (fun a x ->
+          match a with
+          | Var "" -> x.targets
+          | _ -> Or (a, x.targets)
+        ) (Var "") ([x] @ duplicates) } in
         m::loop rest
   in
   loop xml
@@ -247,7 +297,7 @@ let get_modules_of_config = fun ?target ?verbose af_xml fp_xml ->
   singletonize_modules ?verbose ?target (af_modules @ fp_modules)
 
 (** [get_modules_name xml]
-    * Returns a list of loaded modules' name *)
+ * Returns a list of loaded modules' name *)
 let get_modules_name = fun xml ->
   let target = try Sys.getenv "TARGET" with _ -> "" in
   (* extract all modules sections for a given target *)
@@ -271,12 +321,11 @@ let is_element_unselected = fun ?(verbose=false) target modules name ->
     let xml = ExtXml.parse_file name in
     match Xml.tag xml with
     | "settings" ->
-        let targets = Xml.attrib xml "target" in
-        let target_list = Str.split (Str.regexp "|") targets in
+        let target_list = targets_of_field xml "" in
         let unselected = not (test_targets target target_list) in
-        if unselected && verbose then
+        if unselected && not (target_list = Var ("")) && verbose then
           begin Printf.printf "Info: settings '%s' unloaded for target '%s'\n" name target; flush stdout end;
-        unselected
+        unselected && not (target_list = Var (""))
     | "module" ->
         let unselected = List.for_all (fun m -> m.file <> name) modules in
         if unselected && verbose then
@@ -285,10 +334,10 @@ let is_element_unselected = fun ?(verbose=false) target modules name ->
           if verbose then
             (* display possible unloading of settings when the module itself is loaded *)
             List.iter (fun n ->
-              let tag = Xml.tag n
-              and targets = ExtXml.attrib_or_default n "target" "" in
-              let valid = test_targets target (Str.split (Str.regexp "|") targets) in
-              if tag = "settings" && not (targets = "") && not valid then
+              let tag = Xml.tag n in
+              let target_list = targets_of_field n "" in
+              let valid = test_targets target target_list in
+              if tag = "settings" && not (ExtXml.attrib_or_default n "target" "" = "") && not valid then
                 begin Printf.printf "Info: settings of module '%s' unloaded for target '%s'\n" name target; flush stdout end;
             ) (Xml.children xml)
         end;
diff --git a/sw/lib/ocaml/gen_common.mli b/sw/lib/ocaml/gen_common.mli
index 3c278de910..13c4e4e5b6 100644
--- a/sw/lib/ocaml/gen_common.mli
+++ b/sw/lib/ocaml/gen_common.mli
@@ -22,6 +22,13 @@
  *
  *)
 
+(* simple boolean expressions *)
+type bool_expr =
+  | Var of string
+  | Not of bool_expr
+  | And of bool_expr * bool_expr
+  | Or of bool_expr * bool_expr
+
 (* Module configuration:
   * Xml node
   * file (with path)
@@ -30,7 +37,7 @@
   * parameters
   * extrat targets
   *)
-type module_conf = { name : string; xml : Xml.xml; file : string; filename : string; vpath : string option; param : Xml.xml list; targets : string list; }
+type module_conf = { name : string; xml : Xml.xml; file : string; filename : string; vpath : string option; param : Xml.xml list; targets : bool_expr; }
 
 (* Modules directory *)
 val modules_dir : string
@@ -39,13 +46,13 @@ val modules_dir : string
 val singletonize : ?compare: ('a -> 'a -> int) -> 'a list -> 'a list
 
 (** [targets_of_field] Xml node, default
- * Returns the targets of a makefile node in modules
+ * Returns the targets expression of a makefile node in modules
  * Default "ap|sim" *)
-val targets_of_field : Xml.xml -> string -> string list
+val targets_of_field : Xml.xml -> string -> bool_expr
 
 exception Subsystem of string
 val module_name : Xml.xml -> string
-val get_module : Xml.xml -> string list -> module_conf
+val get_module : Xml.xml -> bool_expr -> module_conf
 
 (** [get_modules_of_airframe xml]
  * Returns a list of pair (modules ("load" node), targets) from airframe file *)
@@ -63,10 +70,10 @@ val get_modules_of_config : ?target:string -> ?verbose:bool -> Xml.xml -> Xml.xm
 (** [test_targets target targets]
  * Test if [target] is allowed [targets]
  * Return true if target is allowed, false if target is not in list or rejected (prefixed by !) *)
-val test_targets : string -> string list -> bool
+val test_targets : string -> bool_expr -> bool
 
-(** [get_targets_of_module xml] Returns the list of targets of a module *)
-val get_targets_of_module : Xml.xml -> string list
+(** [get_targets_of_module xml] Returns the boolean expression of targets of a module *)
+val get_targets_of_module : Xml.xml -> bool_expr
 
 (** [get_modules_name xml]
  * Returns a list of loaded modules' name *)
diff --git a/sw/tools/generators/gen_aircraft.ml b/sw/tools/generators/gen_aircraft.ml
index 2fbe24fafa..e9f7c749b3 100644
--- a/sw/tools/generators/gen_aircraft.ml
+++ b/sw/tools/generators/gen_aircraft.ml
@@ -253,8 +253,8 @@ let parse_firmware = fun makefile_ac ac_xml firmware fp ->
     List.iter (fun def -> define_xml2mk makefile_ac def) defines;
     List.iter (fun def -> define_xml2mk makefile_ac def) t_defines;
     List.iter (module_xml2mk makefile_ac target_name firmware_name) modules;
-    List.iter (fallback_subsys_xml2mk makefile_ac [] firmware target_name) mods;
-    List.iter (fallback_subsys_xml2mk makefile_ac [] firmware target_name) t_mods;
+    List.iter (fallback_subsys_xml2mk makefile_ac (Gen_common.Var "") firmware target_name) mods;
+    List.iter (fallback_subsys_xml2mk makefile_ac (Gen_common.Var "") firmware target_name) t_mods;
     List.iter (subsystem_xml2mk makefile_ac firmware) t_subsystems;
     List.iter (subsystem_xml2mk makefile_ac firmware) subsystems;
     fprintf makefile_ac "\nendif # end of target '%s'\n\n" target_name