diff --git a/conf/firmwares/subsystems/fixedwing/gps_mediatek_diy.makefile b/conf/firmwares/subsystems/shared/gps_mediatek_diy.makefile
similarity index 100%
rename from conf/firmwares/subsystems/fixedwing/gps_mediatek_diy.makefile
rename to conf/firmwares/subsystems/shared/gps_mediatek_diy.makefile
diff --git a/sw/airborne/subsystems/gps/gps_mtk.c b/sw/airborne/subsystems/gps/gps_mtk.c
index d5b35dc5bf..094ef6b71f 100644
--- a/sw/airborne/subsystems/gps/gps_mtk.c
+++ b/sw/airborne/subsystems/gps/gps_mtk.c
@@ -19,7 +19,7 @@
  * Boston, MA 02111-1307, USA.
  */
 
-/** @file gps_mtk.h
+/** @file gps_mtk.c
  * @brief Mediatek MT3329 specific code
  *
  * supports:
@@ -139,7 +139,7 @@ void gps_mtk_msg(void)
 }
 
 static void gps_mtk_time2itow(uint32_t  gps_date, uint32_t  gps_time,
-                              int16_t *gps_week, uint32_t *gps_itow)
+                              uint16_t *gps_week, uint32_t *gps_itow)
 {
   /* convert UTC date/time to GPS week/itow, we have no idea about GPS
      leap seconds for now */
diff --git a/sw/airborne/subsystems/gps/gps_mtk.h b/sw/airborne/subsystems/gps/gps_mtk.h
index 26163c94b4..b416a43b4f 100644
--- a/sw/airborne/subsystems/gps/gps_mtk.h
+++ b/sw/airborne/subsystems/gps/gps_mtk.h
@@ -19,6 +19,17 @@
  * Boston, MA 02111-1307, USA.
  */
 
+/** @file gps_mtk.h
+ * @brief Mediatek MT3329 specific code
+ *
+ * supports:
+ *   DIYDrones V1.4 protocol (AXN1.30_2278)
+ *   DIYDrones V1.6 protocol (AXN1.30_2389)
+ *
+ * documentation is partly incorrect, see mtk.xml for what seems
+ * to be "real"
+ *
+ */
 
 #ifndef MTK_H
 #define MTK_H
@@ -57,6 +68,8 @@ extern struct GpsMtk gps_mtk;
 #include "pprzlink/pprzlink_device.h"
 
 #ifdef GPS_CONFIGURE
+extern void gps_configure(void);
+extern void gps_configure_uart(void);
 extern bool_t gps_configuring;
 #define GpsConfigure() {            \
     if (gps_configuring)            \
@@ -68,6 +81,7 @@ extern bool_t gps_configuring;
 
 extern void gps_mtk_read_message(void);
 extern void gps_mtk_parse(uint8_t c);
+extern void gps_mtk_msg(void);
 
 static inline void GpsEvent(void)
 {
@@ -82,12 +96,4 @@ static inline void GpsEvent(void)
   }
 }
 
-/*
- * dynamic GPS configuration
- */
-#ifdef GPS_CONFIGURE
-extern void gps_configure(void);
-extern void gps_configure_uart(void);
-#endif
-
 #endif /* MTK_H */
diff --git a/sw/tools/generators/gen_mtk.ml b/sw/tools/generators/gen_mtk.ml
index 835d9292ff..ec34e99c1c 100644
--- a/sw/tools/generators/gen_mtk.ml
+++ b/sw/tools/generators/gen_mtk.ml
@@ -105,7 +105,8 @@ let parse_message = fun class_name m ->
       if l <> !offset then raise (Length_error (m, l, !offset))
     with
         Xml.No_attribute("length") -> () (** Undefined length authorized *)
-  end
+  end;
+  fprintf out "\n#define MTK_%s_%s_LENGTH %d\n" class_name msg_name !offset
 
 
 let parse_class = fun c ->