added code_unit attribute to section defines in airframe file parsing

always convert degrees to radians, unless explicitly stated otherwise
* if unit and code_unit are specified the value is converted to code_unit and then written to the generated airframe.h file
* this works for default units like deg<->rad, m<->mm, etc.
* only works if the contents of the value attribute can be converted to float, otherwise string is simply copied
* special treatment for unit="deg": if code_unit is not specified, will be converted to rad nevertheless, if this is not wanted explicitly specify code_unit="deg"

conf/airframes/airframe.dtd

@@ -97,6 +97,7 @@ value CDATA #REQUIRED>
 name CDATA #REQUIRED
 value CDATA #IMPLIED
 unit CDATA #IMPLIED
+code_unit CDATA #IMPLIED
 integer CDATA #IMPLIED>
 
 <!ATTLIST configure

sw/tools/gen_airframe.ml

@@ -26,6 +26,8 @@
 
 let max_pprz = 9600. (* !!!! MAX_PPRZ From paparazzi.h !!!! *)
 
+exception Undefined_scale
+
 open Printf
 open Xml2h
 
@@ -80,11 +82,30 @@ let define_integer name v n =
   in
   continious_frac (truncate v) v (1, (truncate v)) (0, 1)
 
+let code_unit_scale_of_tag = function t ->
+  let u = try ExtXml.attrib t "unit" with _ -> "" in
+  let cu = try ExtXml.attrib t "code_unit" with _ -> "" in
+  match (u, cu) with
+      ("deg", "rad") | ("deg/s", "rad/s") -> Latlong.pi /. 180.
+    | ("deg", "") | ("deg/s", "") -> Latlong.pi /. 180.
+    | ("rad", "deg") | ("rad/s", "deg/s") -> 180. /. Latlong.pi
+    | ("m", "cm") | ("m/s", "cm/s") -> 100.
+    | ("cm", "m") | ("cm/s", "m/s") -> 0.01
+    | ("m", "mm") | ("m/s", "mm/s") -> 1000.
+    | ("mm", "m") | ("mm/s", "m/s") -> 0.001
+    | ("decideg", "deg") -> 0.1
+    | ("deg", "decideg") -> 10.
+    | (_, _) -> raise Undefined_scale
+
 let parse_element = fun prefix s ->
   match Xml.tag s with
       "define" -> begin
         try
-        define (prefix^ExtXml.attrib s "name") (ExtXml.display_entities (ExtXml.attrib s "value"));
+          try
+            let value = (ExtXml.float_attrib s "value") *. (code_unit_scale_of_tag s) in
+            define (prefix^ExtXml.attrib s "name") (string_of_float value);
+          with
+              _ -> define (prefix^ExtXml.attrib s "name") (ExtXml.display_entities (ExtXml.attrib s "value"));
           define_integer (prefix^(ExtXml.attrib s "name")) (ExtXml.float_attrib s "value") (ExtXml.int_attrib s "integer");
         with _ -> ();
       end