getBufferedData

Gets data from the real-time application instrument buffer

Since R2022b

Syntax

map_object = getBufferedData(instrument_object)

Description

map_object = getBufferedData(instrument_object) gets data from buffer on the target computer for real-time application instrument.

In normal (non-buffered) data mode, an instrument for a real-time application can be configured with a callback that gets executed each time data is available. The normal data mode operation of an instrument pushes the data to the callback.

In buffered data mode (when the instrument.BufferedData flag is enabled), the callback configured for the instrument is not executed when data arrives. Instead, the real-time application stores the data and an app (for example, an instrument panel app) can retrieve the data by using the getBufferedData function. The call to this function returns the buffered data, then the function deletes the data from the instrument. The instrument continues to buffer new data until the next call to the getBufferedData function. The buffered mode operation of an instrument lets the app pull the data from the instrument.

An example situation for buffered data mode is the case when callbacks cannot be executed through the Python-MATLAB bridge. When you create an instrument from Python code, there is no way for the instrument to execute a callback in Python because the Python-MATLAB API does not support callbacks. The buffered data mode lets you get the data from the instrument by requesting it.

Examples

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Get Buffered Data for Instrument

Get buffered data for a real-time application instrument by using the getBufferedData function. The function gets data that is buffered from the time that you change the real-time application from normal (not buffered) data mode to buffered data mode by enabling the Instrument.BufferedData flag. This flag only affects the operation of the getBufferedData function.

mldatxfile = 'slrt_ex_tank.mldatx';
hInst = slrealtime.Instrument(mldatxfile);
connectCallback(hInst,@my_callback);
addSignal(hInst,'slrt_ex_tank/ControlValue',1);
% . . . change from normal (not buffered) data mode 
% . . . change to buffered data mode
Instrument.BufferedData = "true";
% . . . inside the my_callback (an slrealtime.instrument callback), 
% . . . you can call getBufferedData
myData = getBufferedData(hInst);