diff --git a/sw/lib/ocaml/Makefile b/sw/lib/ocaml/Makefile
index 48eff1ad8c..9a6df20b4d 100644
--- a/sw/lib/ocaml/Makefile
+++ b/sw/lib/ocaml/Makefile
@@ -26,6 +26,7 @@ INCLUDES= -I +xml-light -I +pcre -I +netstring
 XINCLUDES= -I +lablgl -I +lablgtk2 -I +xml-light
 OCAMLC=ocamlc
 OCAMLOPT=ocamlopt
+OCAMLLIBDIR=$(shell ocamlc -where)
 
 
 SRC = debug.ml base64.ml serial.ml ocaml_tools.ml extXml.ml env.ml xml2h.ml latlong.ml srtm.ml http.ml gm.ml iGN.ml geometry_2d.ml cserial.o convert.o ubx.ml pprz.ml xbee.ml xmlCom.ml editAirframe.ml
@@ -77,6 +78,12 @@ ml_gtkgl_hack.o   : ml_gtkgl_hack.c
 	@echo OC $<
 	$(Q)$(OCAMLC) $(INCLUDES) -c -ccopt "$(GTKCFLAGS)" $<
 
+camltm.o : register_example.cmo
+	$(OCAMLC) $(INCLUDES) -output-obj -o $@ unix.cma str.cma xml-light.cma ivy-ocaml.cma debug.cmo serial.cmo extXml.cmo env.cmo pprz.cmo tm.cmo
+
+caml_from_c_example : cserial.o convert.o caml_from_c_example.o camltm.o
+	$(CC) -o $@ $^ -L$(OCAMLLIBDIR) -lunix -lstr -livy-ocaml -lcamlrun -lm -livy -lcurses
+
 %.cmo : %.ml
 	@echo OC $<
 	$(Q)$(OCAMLC) $(INCLUDES) -c $<
diff --git a/sw/lib/ocaml/caml_from_c_example.c b/sw/lib/ocaml/caml_from_c_example.c
new file mode 100644
index 0000000000..7d3b089325
--- /dev/null
+++ b/sw/lib/ocaml/caml_from_c_example.c
@@ -0,0 +1,30 @@
+#include <stdio.h>
+#include <string.h>
+#include <caml/mlvalues.h>
+#include <caml/callback.h>
+#include <caml/memory.h>
+#include <caml/alloc.h>
+#include <caml/custom.h>
+
+
+void print_ascii_to_binary(int n, char* msg)
+{
+  static value * caml_to_binary_closure = NULL;
+  if (caml_to_binary_closure == NULL)
+    caml_to_binary_closure = caml_named_value("to_binary");
+  
+  value s = caml_callback2(*caml_to_binary_closure, Val_int(n), caml_copy_string(msg));
+
+  int i;
+  for(i = 0; i < string_length(s); i++)
+    printf("%02x ", Byte_u(s, i));
+  printf("\n");
+}
+
+int main(int argc, char** argv) {
+  caml_startup(argv);
+  
+  print_ascii_to_binary(42, "ATTITUDE 7 22 33");
+  
+  return 0;
+}
diff --git a/sw/lib/ocaml/register_example.ml b/sw/lib/ocaml/register_example.ml
new file mode 100644
index 0000000000..64b99a9d98
--- /dev/null
+++ b/sw/lib/ocaml/register_example.ml
@@ -0,0 +1,10 @@
+module Tm_Pprz = Pprz.Messages (struct let name = "telemetry" end)
+
+let to_binary = fun ac_id m ->
+  let msg_id, vs = Tm_Pprz.values_of_string m in
+  let payload = Tm_Pprz.payload_of_values msg_id ac_id vs in
+  let buf = Pprz.Transport.packet payload in
+  Printf.printf "From caml: %s\n%!" (Debug.xprint buf);
+  buf
+
+let _ = Callback.register "to_binary" to_binary