diff --git a/sw/airborne/downlink_transport.h b/sw/airborne/downlink_transport.h
index 74dadb975d..83b6022902 100644
--- a/sw/airborne/downlink_transport.h
+++ b/sw/airborne/downlink_transport.h
@@ -52,7 +52,7 @@ struct DownlinkTransport
 	uint8_t (*SizeOf)(void *impl, uint8_t size);
 	int (*CheckFreeSpace)(void *impl, uint8_t size);
 
-	void (*PutBytes)(void *impl, enum DownlinkDataType data_type, uint8_t len, const uint8_t *bytes);
+	void (*PutBytes)(void *impl, enum DownlinkDataType data_type, uint8_t len, const void *bytes);
 
 	void (*StartMessage)(void *impl, char *name, uint8_t msg_id, uint8_t payload_len);
 	void (*EndMessage)(void *impl);
diff --git a/sw/airborne/fms/onboard_transport.c b/sw/airborne/fms/onboard_transport.c
index 736a9b2121..25a04cd69a 100644
--- a/sw/airborne/fms/onboard_transport.c
+++ b/sw/airborne/fms/onboard_transport.c
@@ -14,13 +14,13 @@
 #define FILENAME_LEN 64
 #define TIMESTAMP_SCALE 10000
 
-static void put_bytes(void *impl, enum DownlinkDataType data_type, uint8_t len __attribute__((unused)), const uint8_t *bytes)
+static void put_bytes(void *impl, enum DownlinkDataType data_type, uint8_t len __attribute__((unused)), const void *bytes)
 {
   struct onboard_transport *onboard = (struct onboard_transport *) impl;
   uint32_t length = 0;
 
   if (data_type == DL_TYPE_ARRAY_LENGTH) {
-    onboard->array_length = (uint8_t) *bytes;
+    onboard->array_length = *((const uint8_t *) bytes);
     return;
   }
 
@@ -32,48 +32,48 @@ static void put_bytes(void *impl, enum DownlinkDataType data_type, uint8_t len _
     }
     switch (data_type) {
       case DL_TYPE_UINT8:
-        onboard->buffer_idx += snprintf(onboard->buffer + onboard->buffer_idx, ONBOARD_BUFFER_LEN - onboard->buffer_idx, "%hhu", *bytes);
-        bytes = bytes + 1;
+        onboard->buffer_idx += snprintf(onboard->buffer + onboard->buffer_idx, ONBOARD_BUFFER_LEN - onboard->buffer_idx, "%hhu", * (const uint8_t *)bytes);
+        bytes = (const uint8_t *) bytes + 1;
         break;
       case DL_TYPE_UINT16:
         onboard->buffer_idx += snprintf(onboard->buffer + onboard->buffer_idx, ONBOARD_BUFFER_LEN - onboard->buffer_idx, "%hu", * (const uint16_t *)bytes);
-        bytes = bytes + 2;
+        bytes = (const uint16_t *) bytes + 2;
         break;
       case DL_TYPE_UINT32:
         onboard->buffer_idx += snprintf(onboard->buffer + onboard->buffer_idx, ONBOARD_BUFFER_LEN - onboard->buffer_idx, "%u", * (const uint32_t *)bytes);
-        bytes = bytes + 4;
+        bytes = (const uint32_t *) bytes + 4;
         break;
       case DL_TYPE_UINT64:
         onboard->buffer_idx += snprintf(onboard->buffer + onboard->buffer_idx, ONBOARD_BUFFER_LEN - onboard->buffer_idx, "%llu", *(const uint64_t *)bytes);
-        bytes = bytes + 8;
+        bytes = (const uint64_t *) bytes + 8;
         break;
       case DL_TYPE_INT8:
         onboard->buffer_idx += snprintf(onboard->buffer + onboard->buffer_idx, ONBOARD_BUFFER_LEN - onboard->buffer_idx, "%hhi", * (const int8_t *)bytes);
-        bytes = bytes + 1;
+        bytes = (const int8_t *) bytes + 1;
         break;
       case DL_TYPE_INT16:
         onboard->buffer_idx += snprintf(onboard->buffer + onboard->buffer_idx, ONBOARD_BUFFER_LEN - onboard->buffer_idx, "%hi", * (const int16_t *)bytes);
-        bytes = bytes + 2;
+        bytes = (const int16_t *) bytes + 2;
         break;
       case DL_TYPE_INT32:
         onboard->buffer_idx += snprintf(onboard->buffer + onboard->buffer_idx, ONBOARD_BUFFER_LEN - onboard->buffer_idx, "%i", * (const int32_t *)bytes);
-        bytes = bytes + 4;
+        bytes = (const int32_t *) bytes + 4;
         break;
       case DL_TYPE_INT64:
         onboard->buffer_idx += snprintf(onboard->buffer + onboard->buffer_idx, ONBOARD_BUFFER_LEN - onboard->buffer_idx, "%lli", *(const int64_t *)bytes);
-        bytes = bytes + 8;
+        bytes = (const int64_t *) bytes + 8;
         break;
       case DL_TYPE_FLOAT:
         onboard->buffer_idx += snprintf(onboard->buffer + onboard->buffer_idx, ONBOARD_BUFFER_LEN - onboard->buffer_idx, "%#f", *(const float *)bytes);
-        bytes = bytes + 4;
+        bytes = (const float *) bytes + 4;
         break;
       case DL_TYPE_DOUBLE:
         onboard->buffer_idx += snprintf(onboard->buffer + onboard->buffer_idx, ONBOARD_BUFFER_LEN - onboard->buffer_idx, "%#f", *(const double *)bytes);
-        bytes = bytes + 8;
+        bytes = (const double *) bytes + 8;
         break;
       case DL_TYPE_TIMESTAMP:
         onboard->buffer_idx += snprintf(onboard->buffer + onboard->buffer_idx, ONBOARD_BUFFER_LEN - onboard->buffer_idx, "%u.%04u", (*(const uint32_t *)bytes) / TIMESTAMP_SCALE,(*(const uint32_t *)bytes) % TIMESTAMP_SCALE);
-        bytes = bytes + 4;
+        bytes = (const uint32_t *) bytes + 4;
         break;
       case DL_TYPE_ARRAY_LENGTH:
         break;
diff --git a/sw/airborne/fms/udp_transport2.c b/sw/airborne/fms/udp_transport2.c
index 175725f5d0..4cd448157f 100644
--- a/sw/airborne/fms/udp_transport2.c
+++ b/sw/airborne/fms/udp_transport2.c
@@ -22,9 +22,10 @@ static void put_named_uint8_t(struct udp_transport *udp, char *name __attribute_
   put_uint8_t(udp, byte);
 }
 
-static void put_bytes(void *impl, enum DownlinkDataType data_type __attribute__((unused)), uint8_t len, const uint8_t *bytes)
+static void put_bytes(void *impl, enum DownlinkDataType data_type __attribute__((unused)), uint8_t len, const void *buf)
 {
   struct udp_transport *udp = (struct udp_transport *) impl;
+	const uint8_t *bytes = (const uint8_t *) buf;
   for (int i = 0; i < len; i++) {
     put_uint8_t(udp, bytes[i]);
   }
@@ -38,7 +39,7 @@ static void header(struct udp_transport *udp, uint8_t payload_len)
   uint8_t msg_len = payload_len + PPRZ_PROTOCOL_OVERHEAD;
   udp->udpt_ck_a = udp->udpt_ck_b = 0;
   put_uint8_t(udp, msg_len);
-  put_bytes(udp, DL_TYPE_UINT32, 4, (uint8_t *) &msg_timestamp);
+  put_bytes(udp, DL_TYPE_UINT32, 4, &msg_timestamp);
 }
 
 static void start_message(void *impl, char *name, uint8_t msg_id, uint8_t payload_len)
diff --git a/sw/tools/gen_messages2.ml b/sw/tools/gen_messages2.ml
index b099e8383d..79e92fdb60 100644
--- a/sw/tools/gen_messages2.ml
+++ b/sw/tools/gen_messages2.ml
@@ -139,11 +139,11 @@ module Gen_onboard = struct
   let print_field = fun h (t, name, (_f: format option)) ->
     match t with 
       Basic _ ->
-	fprintf h "\t  tp->PutBytes(tp->impl, %s, %s, (uint8_t *) _%s); \n" (dl_type (Syntax.nameof t)) (Syntax.sizeof t) name
+	fprintf h "\t  tp->PutBytes(tp->impl, %s, %s, (void *) _%s); \n" (dl_type (Syntax.nameof t)) (Syntax.sizeof t) name
     | Array (t, varname) ->
 	let _s = Syntax.sizeof (Basic t) in
-	fprintf h "\t  tp->PutBytes(tp->impl, DL_TYPE_ARRAY_LENGTH, 1, (uint8_t *) &%s); \n" (Syntax.length_name varname);
-	fprintf h "\t  tp->PutBytes(tp->impl, %s, %s * %s, (uint8_t *) _%s); \n" (dl_type (Syntax.nameof (Basic t))) (Syntax.sizeof (Basic t)) (Syntax.length_name varname) name
+	fprintf h "\t  tp->PutBytes(tp->impl, DL_TYPE_ARRAY_LENGTH, 1, (void *) &%s); \n" (Syntax.length_name varname);
+	fprintf h "\t  tp->PutBytes(tp->impl, %s, %s * %s, (void *) _%s); \n" (dl_type (Syntax.nameof (Basic t))) (Syntax.sizeof (Basic t)) (Syntax.length_name varname) name
 
   let print_parameter h = function
       (Array (t, varname), s, _) -> fprintf h "uint8_t %s, %s *_%s" (Syntax.length_name s) (c_type (Syntax.nameof (Basic t))) s