diff --git a/Makefile b/Makefile
index 6f6057d2de..cb8aacb44b 100644
--- a/Makefile
+++ b/Makefile
@@ -81,7 +81,7 @@ SUBDIRS = $(PPRZCENTER) $(MISC) $(LOGALIZER)
 #
 # xml files used as input for header generation
 #
-MESSAGES_XML = $(CONF)/messages.xml
+CUSTOM_MESSAGES_XML = $(CONF)/messages.xml
 ABI_XML = $(CONF)/abi.xml
 UBX_XML = $(CONF)/ubx.xml
 MTK_XML = $(CONF)/mtk.xml
@@ -186,12 +186,12 @@ static_h: pprzlink_protocol $(GEN_HEADERS)
 pprzlink_protocol :
 	$(Q)test -d $(STATICINCLUDE) || mkdir -p $(STATICINCLUDE)
 	$(Q)test -d $(STATICLIB) || mkdir -p $(STATICLIB)
-ifeq ("$(wildcard $(MESSAGES_XML))","")
+ifeq ("$(wildcard $(CUSTOM_MESSAGES_XML))","")
 	@echo GENERATE $@ with default messages
 	$(Q)Q=$(Q) MESSAGES_INSTALL=$(MESSAGES_INSTALL) $(MAKE) -C $(PPRZLINK_DIR) pymessages
 else
-	@echo GENERATE $@ with custome messages from $(MESSAGES_XML)
-	$(Q)Q=$(Q) MESSAGES_XML=$(MESSAGES_XML) MESSAGES_INSTALL=$(MESSAGES_INSTALL) $(MAKE) -C $(PPRZLINK_DIR) pymessages
+	@echo GENERATE $@ with custome messages from $(CUSTOM_MESSAGES_XML)
+	$(Q)Q=$(Q) MESSAGES_XML=$(CUSTOM_MESSAGES_XML) MESSAGES_INSTALL=$(MESSAGES_INSTALL) $(MAKE) -C $(PPRZLINK_DIR) pymessages
 endif
 
 
diff --git a/Makefile.ac b/Makefile.ac
index 5e05dfba78..4644b38ab0 100644
--- a/Makefile.ac
+++ b/Makefile.ac
@@ -28,9 +28,10 @@ include conf/Makefile.local
 # main directory where the generated files and compilation results for an aircraft are stored
 AIRCRAFT_BUILD_DIR = $(PAPARAZZI_HOME)/var/aircrafts/$(AIRCRAFT)
 CONF=$(PAPARAZZI_HOME)/conf
+VAR=$(PAPARAZZI_HOME)/var
 CONF_XML ?= $(CONF)/conf.xml
 AIRBORNE=sw/airborne
-MESSAGES_XML = $(CONF)/messages.xml
+MESSAGES_XML = $(VAR)/messages.xml
 
 # make sure the TARGET variable is set if needed for current make target
 ifneq (,$(findstring $(MAKECMDGOALS),all_ac_h radio_ac_h flight_plan_ac_h))
diff --git a/conf/messages.dtd b/conf/abi.dtd
similarity index 75%
rename from conf/messages.dtd
rename to conf/abi.dtd
index 2e6072565f..f7d3822707 100644
--- a/conf/messages.dtd
+++ b/conf/abi.dtd
@@ -10,7 +10,6 @@
 <!ATTLIST message
   name CDATA #REQUIRED
   id   CDATA #REQUIRED
-  link CDATA #IMPLIED
 >
 
 <!ELEMENT description (#PCDATA)>
@@ -19,10 +18,6 @@
 <!ATTLIST field
   name CDATA #REQUIRED
   type CDATA #REQUIRED
-  format CDATA #IMPLIED
   unit CDATA #IMPLIED
-  values CDATA #IMPLIED
-  alt_unit CDATA #IMPLIED
-  alt_unit_coef CDATA #IMPLIED
 >
 
diff --git a/conf/abi.xml b/conf/abi.xml
index 5d4008727e..28765f31d5 100644
--- a/conf/abi.xml
+++ b/conf/abi.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0"?>
-<!DOCTYPE protocol SYSTEM "messages.dtd">
+<!DOCTYPE protocol SYSTEM "abi.dtd">
 <protocol>
 
   <msg_class name="airborne">
diff --git a/sw/ext/pprzlink b/sw/ext/pprzlink
index 5f11dfd389..2839929e9c 160000
--- a/sw/ext/pprzlink
+++ b/sw/ext/pprzlink
@@ -1 +1 @@
-Subproject commit 5f11dfd38988e1834c6b6a0186c0baba3913c4ae
+Subproject commit 2839929e9c4e39d005acd0a7e83ca08a3ccd9157
diff --git a/sw/ground_segment/tmtc/server.ml b/sw/ground_segment/tmtc/server.ml
index 30af64a196..584d9d1a7c 100644
--- a/sw/ground_segment/tmtc/server.ml
+++ b/sw/ground_segment/tmtc/server.ml
@@ -533,7 +533,7 @@ let new_aircraft = fun get_alive_md5sum real_id ->
 
   ignore (Glib.Timeout.add 1000 (fun _ -> update (); true));
 
-  let messages_xml = Xml.parse_file (Env.paparazzi_home // root_dir // "conf" // "messages.xml") in
+  let messages_xml = Xml.parse_file (Env.paparazzi_home // root_dir // "var" // "messages.xml") in
   ac, messages_xml
 
 let check_alerts = fun a ->
diff --git a/sw/logalizer/matlab_log/dialog.m b/sw/logalizer/matlab_log/dialog.m
index 06aee49d61..a16cbf76c8 100644
--- a/sw/logalizer/matlab_log/dialog.m
+++ b/sw/logalizer/matlab_log/dialog.m
@@ -161,9 +161,9 @@ X0=0;
 try
     node=xmlread(fullfile(pp_home,'messages.xml'));
 catch
-    warning('messages.xml not found. trying conf/messages.xml...')
+    warning('messages.xml not found. trying var/messages.xml...')
     try
-        node=xmlread(fullfile(pp_home,'conf/messages.xml'));
+        node=xmlread(fullfile(pp_home,'var/messages.xml'));
     catch
         warning('messages.xml not found. Exiting...');
         close(gcf);
diff --git a/sw/logalizer/play_core.ml b/sw/logalizer/play_core.ml
index bb54b58a8f..67c06e4f03 100644
--- a/sw/logalizer/play_core.ml
+++ b/sw/logalizer/play_core.ml
@@ -83,7 +83,7 @@ let store_conf = fun conf acs ->
   write_xml (replay_dir // "conf" // "conf.xml") orig_conf
 
 let store_messages = fun protocol ->
-  write_xml (replay_dir // "conf" // "messages.xml") protocol
+  write_xml (replay_dir // "var" // "messages.xml") protocol
 
 let time_of = fun (t, _, _) -> t
 
diff --git a/sw/simulator/data.ml b/sw/simulator/data.ml
index 05c4fe7918..f28d6d3c51 100644
--- a/sw/simulator/data.ml
+++ b/sw/simulator/data.ml
@@ -26,14 +26,13 @@ open Printf
 
 let (//) = Filename.concat
 
-(* let pprz_conf_path = Env.paparazzi_src // "conf" *)
 let user_conf_path = Env.paparazzi_home // "conf"
+let user_var_path = Env.paparazzi_home // "var"
 
 let conf_xml = Xml.parse_file (user_conf_path // "conf.xml")
 
 let messages_ap =
-(*  let xml = Xml.parse_file (pprz_conf_path // "messages.xml") in *)
-  let xml = Xml.parse_file (user_conf_path // "messages.xml") in
+  let xml = Xml.parse_file (user_var_path // "messages.xml") in
   try
     ExtXml.child xml ~select:(fun x -> Xml.attrib x "name" = "telemetry") "msg_class"
   with
diff --git a/sw/tools/find_free_msg_id.ml b/sw/tools/find_free_msg_id.ml
index c0f1b11072..be85f9391a 100644
--- a/sw/tools/find_free_msg_id.ml
+++ b/sw/tools/find_free_msg_id.ml
@@ -32,7 +32,7 @@
 (** FIXME: Get file names with Arg.parse *)
 
 let (//) =  Filename.concat
-let messages_xml = Env.paparazzi_home // "conf" // "messages.xml"
+let messages_xml = Env.paparazzi_home // "var" // "messages.xml"
 
 let nb_msg = 255