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OPUS Projektor Manual
Variables
If flickering back to last known value is not acceptable and the GUI can make sure that all
settings made are valid then PClient could become the owner which would mean that
any value of the variable is valid and variable will stay valid at any point of time.
If display should forward the value owned by PClient to different busses it will forward
each and every value modification made by anyone - because it considers all
modifications valid.
Remanent Variables
Remanent variables keep their values over power cycles. They get re-initialized whenever a
new PClient is installed on the display.
Remanent variables are intended for operator settings and other values which will change
but whose last value should be remembered when PClient is started again.
Predefined Variables
On the display there is a variety of predefined variables you can directly use in your GUI.
They provide e.g. hardware states such as I/O values for digital and analog ports or CAN
bus status as well as display specific properties e.g. the part number and serial number.
Predefined variables are also used to e.g. configure camera interfaces, display backlight
or beeper activity and obtain and set current time as provided by real time clock (RTC).
Other predefined variables provide information specific to your GUI, e.g. dealing with virtual
keyboards and alarms and visibility. There are also variables showing the recent pages
visited and the time a page was active.
ISO-VT Variables
There is a range of indices reserved for ISO-VT. These variables are not existing by default
but you can create them as they are defined in the variable table.
This approach allows to save the resources if you don't use ISO-VT on your display while
still providing the information in a standardized manner not interfering with your user
defined variables.
Data Types
Every variable has to have a type. By default character strings and numeric types are
supported.
Numeric types are either signed or unsigned and have a length in bits.
In order to support the minimum requirements of CANopen there are a few predefined data
types which can not be deleted or modified.
Additionally both two bit types are provided which are used for some predefined variables
representing booleans with an additional "undefined / unknown / don't care" state required
e.g. for J1939 protocol.
Note: String variables are intended to carry readable strings. Therefore their value is
considered to end where a "\0" character occurs.
Note: If string values should be shown on display they are interpreted as UTF-8 format
which is the same as ASCII for the first 127 characters only.
Organizing principles
The program provides two separate means of variable organization:
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