Add short software description

README.md

@@ -11,6 +11,27 @@ Wake up a Easylink (A-IVI) car multimedia system by CAN for using it on a table
 
 - Please backup your NOR flash of the unit, if you want to use it with DDT often (you will! why boot a unit on your table), see details below.
 
+## Serial control
+
+If you open a serial terminal to the ESP you will see a summary of all variables which reflects CAN messages sent to the Easylink.
+You can modify these with just typing in.
+
+For example if you want to start the system, type:
+
+```
+iginition on
+````
+
+All CAN frames are now sent.
+
+You can set brightness mode to day or night for example type
+
+```
+brightness night
+```
+
+If you need a new summary of all new states, just hit RETURN without any command.
+
 ## CAN frame capture
 
 I captured some CAN frames on CAN Bus on EXT-CAN and replayed then with a arduino and a can transreceiver.