videv initialisation and periodic status publishing

base.py

 import json
 import logging
+import task
 
 try:
     from config import APP_NAME as ROOT_LOGGER_NAME
         self.__callback_list__ = []
         self.logger = logging.getLogger(ROOT_LOGGER_NAME).getChild("devices")
 
-    def add_callback(self, key, data, callback, on_change_only=False):
+    def add_callback(self, key, data, callback, on_change_only=False, init_now=False):
         """
         key: key or None for all keys
         data: data or None for all data
         cb_tup = (key, data, callback, on_change_only)
         if cb_tup not in self.__callback_list__:
             self.__callback_list__.append(cb_tup)
+        if init_now and self.get(key) is not None:
+            callback(self, key, self[key])
 
     def set(self, key, data, block_callback=[]):
         if key in self.keys():
         super().__init__(mqtt_client, topic, default_values=default_values)
         self.__display_dict__ = {}
         self.__control_dict__ = {}
+        self.__periodic__ = task.periodic(300, self.send_all)
+        self.__periodic__.run()
+
+    def send_all(self, rt):
+        for key in self:
+            if self[key] is not None:
+                self.__tx__(key, self[key])
 
     def add_display(self, my_key, ext_device, ext_key, on_change_only=True):
         """
             # store information to identify callback from ext_device
             self.__display_dict__[(id(ext_device[0]), ext_key)] = my_key
             # register a callback to listen for data from external device
-            ext_device[0].add_callback(ext_key, None, self.__rx_ext_device_data__, on_change_only)
+            ext_device[0].add_callback(ext_key, None, self.__rx_ext_device_data__, on_change_only, init_now=True)
         else:
             # store information to identify callback from ext_device
             self.__display_dict__[(id(ext_device), ext_key)] = my_key
             # register a callback to listen for data from external device
-            ext_device.add_callback(ext_key, None, self.__rx_ext_device_data__, on_change_only)
+            ext_device.add_callback(ext_key, None, self.__rx_ext_device_data__, on_change_only, init_now=True)
         # send initial display data to videv interface
         data = ext_device.get(ext_key)
         if data is not None: