diff --git a/sw/lib/ocaml/ubx.ml b/sw/lib/ocaml/ubx.ml
index 45b7a2fb2f..e4d79ff2f3 100644
--- a/sw/lib/ocaml/ubx.ml
+++ b/sw/lib/ocaml/ubx.ml
@@ -67,16 +67,22 @@ let ubx_get_class = fun name ->
   let ubx_xml = Lazy.force ubx_xml in
   ExtXml.child ubx_xml ~select:(fun x -> ExtXml.attrib x "name" = name) "class"
 
-let ubx_nav () = ubx_get_class "NAV"
-let ubx_nav_id () = int_of_string (ExtXml.attrib (ubx_nav ()) "ID")
 let ubx_get_msg = fun ubx_class name ->
   ExtXml.child ubx_class ~select:(fun x -> ExtXml.attrib x "name" = name) "message"
 
+let ubx_nav () = ubx_get_class "NAV"
+let ubx_nav_id () = int_of_string (ExtXml.attrib (ubx_nav ()) "ID")
+
+let ubx_usr () = ubx_get_class "USR"
+let ubx_usr_id () = int_of_string (ExtXml.attrib (ubx_usr ()) "ID")
+
 let ubx_get_nav_msg = fun name -> ubx_get_msg (ubx_nav ()) name
+let ubx_get_usr_msg = fun name -> ubx_get_msg (ubx_usr ()) name
 
 let nav_posutm () = ubx_nav_id (), ubx_get_nav_msg "POSUTM"
 let nav_status () = ubx_nav_id (), ubx_get_nav_msg "STATUS"
 let nav_velned () = ubx_nav_id (), ubx_get_nav_msg "VELNED"
+let usr_irsim () = ubx_usr_id (), ubx_get_usr_msg "IRSIM"
 
 
 let send_start_sequence = fun gps ->
diff --git a/sw/lib/ocaml/ubx.mli b/sw/lib/ocaml/ubx.mli
index 21d2035d1e..dda5e8413a 100644
--- a/sw/lib/ocaml/ubx.mli
+++ b/sw/lib/ocaml/ubx.mli
@@ -37,4 +37,5 @@ module Protocol :
 val nav_posutm : unit -> int * Xml.xml
 val nav_status : unit -> int * Xml.xml
 val nav_velned : unit -> int * Xml.xml
+val usr_irsim : unit -> int * Xml.xml
 val send : out_channel -> int * Xml.xml -> (string * int) list -> unit
diff --git a/sw/simulator/hitl.ml b/sw/simulator/hitl.ml
index cd324ab2b9..b13966939e 100644
--- a/sw/simulator/hitl.ml
+++ b/sw/simulator/hitl.ml
@@ -45,7 +45,7 @@ module Make(A:Data.MISSION) = struct
     if !tty0 <> "" then uart_mcu0 := open_mcu !tty0;
     if !tty1 <> "" then uart_mcu1 := open_mcu !tty1
 
-  let boot = fun () -> ()
+  let boot = fun time_scale -> ()
 
     let irs =
       try
@@ -57,14 +57,14 @@ module Make(A:Data.MISSION) = struct
 
     let ir_roll_neutral =
       try
-	float_of_string (ExtXml.attrib (ExtXml.child irs ~select:(fun x -> try Xml.attrib x "name" = "ROLL_NEUTRAL_DEFAULT" with Xml.No_attribute _ -> false) "define") "value")
+	int_of_string (ExtXml.attrib (ExtXml.child irs ~select:(fun x -> try Xml.attrib x "name" = "ADC_ROLL_NEUTRAL" with Xml.No_attribute _ -> false) "define") "value")
       with
       Not_found ->
 	failwith "Do not find an ROLL_NEUTRAL_DEFAULT define in IR description" 
     
     let ir_pitch_neutral =
       try
-	float_of_string (ExtXml.attrib (ExtXml.child irs ~select:(fun x -> try Xml.attrib x "name" = "PITCH_NEUTRAL_DEFAULT" with Xml.No_attribute _ -> false) "define") "value")
+	int_of_string (ExtXml.attrib (ExtXml.child irs ~select:(fun x -> try Xml.attrib x "name" = "ADC_PITCH_NEUTRAL" with Xml.No_attribute _ -> false) "define") "value")
       with
 	Not_found ->
 	  failwith "Do not find an PITCH_NEUTRAL_DEFAULT define in IR description"
@@ -76,15 +76,20 @@ module Make(A:Data.MISSION) = struct
 
   open Gps
 
+  let nav_posutm = Ubx.nav_posutm ()
+  let nav_status = Ubx.nav_status ()
+  let nav_velned = Ubx.nav_velned ()
+  let usr_irsim = Ubx.usr_irsim ()
+
   let gps = fun gps ->
     let uart = Unix.out_channel_of_descr !uart_mcu0 in
     let utm = utm_of WGS84 gps.wgs84 in
-    Ubx.send uart Ubx.nav_posutm
+    Ubx.send uart nav_posutm
       ["EAST", scale utm.utm_x 1e2;
        "NORTH", scale utm.utm_y 1e2;
        "ALT", scale gps.alt 1e2];
-    Ubx.send uart Ubx.nav_status ["GPSfix", 3];
-    Ubx.send uart Ubx.nav_velned
+    Ubx.send uart nav_status ["GPSfix", 3];
+    Ubx.send uart nav_velned
       ["ITOW",scale gps.time 1e3;
        "VEL_D", -scale gps.climb 1e2;
        "GSpeed", scale gps.gspeed 1e2;
@@ -96,7 +101,7 @@ module Make(A:Data.MISSION) = struct
     let uart = Unix.out_channel_of_descr !uart_mcu0 in
     let ir_left = ir_left + ir_roll_neutral
     and ir_front = ir_front + ir_pitch_neutral in
-    Ubx.send uart Ubx.usr_irsim
+    Ubx.send uart usr_irsim
       ["ROLL", ir_left;
        "PITCH", ir_front]
 
@@ -109,7 +114,7 @@ module Make(A:Data.MISSION) = struct
 (* nb_servos 2 bytes values, prefixed by 00 ended by \n
    Returns optionaly a function associating the read value to the index *)
   let clock = 16
-  let read_servos = fun servos ->
+  let read_commands = fun servos ->
     let servos_buf = String.create size_servos_buf
     and buf_idx = ref 0 in
     let nb_servos = Array.length servos in
@@ -140,6 +145,6 @@ module Make(A:Data.MISSION) = struct
 
 
 
-  let servos = fun servos ->
-    ignore (GMain.Io.add_watch [`IN] (fun _ -> read_servos servos (); true) (GMain.Io.channel_of_descr !uart_mcu1))
+  let commands = fun commands ->
+    ignore (GMain.Io.add_watch [`IN] (fun _ -> read_commands commands (); true) (GMain.Io.channel_of_descr !uart_mcu1))
 end