reduce communication traffic

- expermental change: no updates of unchanged values within 1 sec
- reduce fast_pollfactor in trinamic
- improve stop behaviour of dpm.DPM

secop/modules.py

@@ -419,6 +419,8 @@ class Module(HasAccessibles):
     def announceUpdate(self, pname, value=None, err=None, timestamp=None):
         """announce a changed value or readerror"""
         pobj = self.parameters[pname]
+        timestamp = timestamp or time.time()
+        changed = pobj.value != value or timestamp > (pobj.timestamp or 0) + 1
         if value is not None:
             pobj.value = value  # store the value even in case of error
         if err:
@@ -431,7 +433,9 @@ class Module(HasAccessibles):
                 pobj.value = pobj.datatype(value)
             except Exception as e:
                 err = secop_error(e)
-        pobj.timestamp = timestamp or time.time()
+            if not changed:
+                return  # experimental: do not update unchanged values within 1 sec
+        pobj.timestamp = timestamp
         pobj.readerror = err
         if pobj.export:
             self.DISPATCHER.announce_update(self.name, pname, pobj)