--- a/svghmi/svghmi.c	Tue Dec 03 09:46:12 2019 +0100
+++ b/svghmi/svghmi.c	Mon Dec 09 10:43:54 2019 +0100
@@ -198,7 +198,11 @@
 {
     bzero(rbuf,sizeof(rbuf));
     bzero(wbuf,sizeof(wbuf));
+
+    pthread_mutex_lock(&svghmi_send_WakeCondLock);
     continue_collect = 1;
+    pthread_cond_signal(&svghmi_send_WakeCond);
+    pthread_mutex_unlock(&svghmi_send_WakeCondLock);
 
     return 0;
 }
@@ -230,12 +234,8 @@
 
     int do_collect;
     pthread_mutex_lock(&svghmi_send_WakeCondLock);
+    pthread_cond_wait(&svghmi_send_WakeCond, &svghmi_send_WakeCondLock);
     do_collect = continue_collect;
-    if(do_collect)
-    {
-        pthread_cond_wait(&svghmi_send_WakeCond, &svghmi_send_WakeCondLock);
-        do_collect = continue_collect;
-    }
     pthread_mutex_unlock(&svghmi_send_WakeCondLock);
 
     if(do_collect) {

--- a/svghmi/svghmi_server.py	Tue Dec 03 09:46:12 2019 +0100
+++ b/svghmi/svghmi_server.py	Mon Dec 09 10:43:54 2019 +0100
@@ -95,18 +95,23 @@
 svghmi_send_thread = None
 
 def SendThreadProc():
-   global svghmi_session
-   size = ctypes.c_uint32()
-   ptr = ctypes.c_void_p()
-   res = 0
-   while True:
-       res=svghmi_send_collect(ctypes.byref(size), ctypes.byref(ptr))
-       if res == 0:
-           # TODO multiclient : dispatch to sessions
-           if svghmi_session is not None:
-               svghmi_session.sendMessage(ctypes.string_at(ptr.value,size.value))
-       elif res not in [errno.EAGAIN, errno.ENODATA]:
-           break
+    global svghmi_session
+    size = ctypes.c_uint32()
+    ptr = ctypes.c_void_p()
+    res = 0
+    while True:
+        res=svghmi_send_collect(ctypes.byref(size), ctypes.byref(ptr))
+        if res == 0:
+            # TODO multiclient : dispatch to sessions
+            if svghmi_session is not None:
+                svghmi_session.sendMessage(ctypes.string_at(ptr.value,size.value))
+        elif res == errno.ENODATA:
+            # this happens when there is no data after wakeup
+            # because of hmi data refresh period longer than PLC common ticktime
+            pass 
+        else:
+            # this happens when finishing
+            break