+ <binary_footer>magic,0x12345678</binary_footer>
+ <binary_footer>length</binary_footer>
+ <binary_footer>none</binary_footer> <!-- default -->
+
+
+
+
+== variable parameters (chunk spec) ===========================================
+
+Both <input> and <output> block can contain a list of <chunk> specs,
+each of which describes the properties of on variable to write/read.
+
+
+ <name> for ease of use (not tranferred)
+ <node> the property tree node which provides the data
+ <type> the value type (needed for formatting)
+ one of string, float, bool, int (default: int)
+ <format> (ASCII protocol only, not used or needed in binary mode)
+ defines the actual piece of text which should be sent.
+ it can include "printf" style formatting options like:
+ <type>
+ %s string
+ %d integer (default)
+ %f float
+
+ <factor> an optional multiplication factor which can be used for
+ unit conversion. (for example, radians to degrees).
+ <offset> an optional offset which can be used for unit conversion.
+ (for example, degrees Celcius to degrees Fahrenheit).
+
+For input chunks there exist some more options:
+
+ <rel> optional boolean parameter to enable handling of incoming values
+ as relative changes (default: false)
+ (Can be eg. used to realise up/down buttons by just sending 1 or
+ -1 respectively)
+
+ <min> an optional minimum limit for the value to be clamped to. This
+ limit is always specified as absolute value, also with relative
+ changes enabled. (default: 0)
+ <max> an optional upper limit for the input value to be clamped to. If
+ <min> equals <max> no limit is applied. (default: 0)
+ <wrap> instead of clamping to minimum and maximum limits, wrap values
+ around. Values will be in [min, max[ (default: false)
+ (Usefull for eg. heading selector to start again with 1 for
+ values higher than 360)
+
+<rel>, <min>, <max> and <wrap> are only used for numeric data types. <rel> can
+additionally be used with type 'bool', where it toggles the value, if the received
+value evaluates to 'true', otherwise the value is left unchanged.
+
+Chunks can also consist of a single constant <format>, like in:
+ <format>Data Section</format>
+
+
+== examples ===================================================================
+
+Writes log of this form: