diff -r 887aba5ef178 -r 3f3b1b8ccba4 svghmi/svghmi.c
--- a/svghmi/svghmi.c	Fri Aug 23 13:01:37 2019 +0200
+++ b/svghmi/svghmi.c	Fri Aug 23 14:01:31 2019 +0200
@@ -39,12 +39,60 @@
     }
 }
 
-void read_iterator(hmi_tree_item_t *dsc){
-    /* todo */
+/* TODO : deduplicate that code with plc_debug.c */
+
+#define __Unpack_case_t(TYPENAME) \
+        case TYPENAME##_ENUM :\
+            *flags = ((__IEC_##TYPENAME##_t *)varp)->flags;\
+            forced_value_p = *real_value_p = &((__IEC_##TYPENAME##_t *)varp)->value;\
+            break;
+
+#define __Unpack_case_p(TYPENAME)\
+        case TYPENAME##_O_ENUM :\
+            *flags = __IEC_OUTPUT_FLAG;\
+        case TYPENAME##_P_ENUM :\
+            *flags |= ((__IEC_##TYPENAME##_p *)varp)->flags;\
+            *real_value_p = ((__IEC_##TYPENAME##_p *)varp)->value;\
+            forced_value_p = &((__IEC_##TYPENAME##_p *)varp)->fvalue;\
+            break;
+
+static void* UnpackVar(hmi_tree_item_t *dsc, void **real_value_p, char *flags)
+{
+    void *varp = dsc->ptr;
+    void *forced_value_p = NULL;
+    *flags = 0;
+    /* find data to copy*/
+    switch(dsc->type){
+        __ANY(__Unpack_case_t)
+        __ANY(__Unpack_case_p)
+    default:
+        break;
+    }
+    if (*flags & __IEC_FORCE_FLAG)
+        return forced_value_p;
+    return *real_value_p;
 }
 
-void write_iterator(hmi_tree_item_t *dsc){
-    /* todo */
+void write_iterator(hmi_tree_item_t *dsc)
+{
+    void *dest_p = &wbuf[dsc->buf_index];
+    void *real_value_p = NULL;
+    char flags = 0;
+
+    void *visible_value_p = UnpackVar(dsc, &real_value_p, &flags);
+
+    memcpy(dest_p, visible_value_p, __get_type_enum_size(dsc->type));
+}
+
+void read_iterator(hmi_tree_item_t *dsc)
+{
+    void *src_p = &rbuf[dsc->buf_index];
+    void *real_value_p = NULL;
+    char flags = 0;
+
+    void *visible_value_p = UnpackVar(dsc, &real_value_p, &flags);
+
+    memcpy(visible_value_p, src_p, __get_type_enum_size(dsc->type));
 }
 
 int __init_svghmi()
@@ -62,6 +110,7 @@
 void __retrieve_svghmi()
 {
     if(!pthread_mutex_lock(&rbuf_mutex)){
+        traverse_hmi_tree(read_iterator);
         pthread_mutex_unlock(&rbuf_mutex);
     }
 }