adding event sources section

Author: OlivierJourdan

www/en/modules/ROOT/images/03-event-sources-ui-fp.png

@@ -3,9 +3,13 @@
 
 == User Interface
 
-The first source of events, you come across when starting with {lv} are the events generated by the UI when a user of your application use the mouse or the keybard.
+The first source of events you come across when starting with {lv} are the events generated by the UI when a user of your application use the mouse or the keybard.
 
-Example code: 01a - Event Sources - User Interface.vi
+The {es} is the way to detect the event and execute the appropriate caode.
+
+NOTE: Before the introduction of the {es} (a long time ago), LabVIEW developpers had to periodically poll the controls to detect interactions with the {ui} 😓.
+
+Example code: *01a - Event Sources - User Interface.vi*
 
 .Front Panel
 image::03-event-sources-ui-fp.png[]
@@ -15,24 +19,53 @@ image::04-event-sources-ui-dg.png[]
 
 == User Events a.k.a Custom Events
 
-
 [quote,John Medland. MLUG October 2020]
 User Events, the worst named feature in {lv}
 
 Behind this name, you'll find the way to create and generate events programmatically.
 
 NOTE: This source of events is the corner stones of many event driven architectures. The https://www.dqmh.org[DQMH framework] is probably one of the most popular framework based on the {lv} user event feature.
 
-Example code: 01b - Event Sources - Custom Events.vi
+Example code: *01b - Event Sources - Custom Events.vi*
 
 .Front Panel
 image::05-event-sources-user-event-fp.png[]
 
 .Diagram
 image::06-event-sources-user-event-dg.png[]
 
-== Callback
+== Event Callback
+
+This source of event doesn't involve the use of an {ev}.
+Once registred to an event the Callback VI is executed each time the event occurs.
+
+NOTE: This kind of event breaks the usal data flow we are used to
+
+// List examples of situation where event callback can be useful  
+
+Example code: *01c - Event Sources - Event Callback.vi*
+
+.Front Panel
+image::07-event-sources-callback-fp.png[]
+
+.Diagram
+image::08-event-sources-callback-dg.png[]
+
+.Callback VI diagram
+image::09-event-sources-callback-vi.png[]
 
 == Daqmx
 
-IMPORTANT: This example requieres the NI Daqmx driver to be executed.
+This source of event is problably the less known.
+With it, you can handle acquistion event in the {es}.
+It makes straigtforward the use of the other sources of events in the loop that handle the acquistion.
+
+IMPORTANT: This example requieres the NI Daqmx driver to be executed.
+
+Example code: *01d - Event Sources - Daqmx Event.vi*
+
+.Front Panel
+image::10-event-sources-daqmx-fp.png[]
+
+.Diagram
+image::11-event-sources-daqmx-dg.png[]