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FSX Request data on sim object not working

J

John Towers

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3
Country
australia
Hi Guys

I am trying to use the simconnect function 'RequestDataOnSimObject' to retrieve data on the following 2 variables:

PLANE_HEADING_DEGREES_TRUE
GPS_WP_TRACK_ANGLE_ERROR

Both variables return data as expected when the PERIOD member for the request data function is set to PERIOD_SECOND, however, I want the data rate to be much faster.
I changed the period to PERIOD_VISUAL_FRAME which worked OK for the plane heading variable, but the GPS variable still only refreshes at the rate of 1 second. The code is the same for handling both variables, so I am wondering if there is a limitation on calling GPS_WP_TRACK_ANGLE_ERROR?

Here is the function call code that I am using:

hr = SimConnect_RequestDataOnSimObject(hSimConnect, REQUEST_PDR, DEFINITION_PDR, SIMCONNECT_OBJECT_ID_USER, SIMCONNECT_PERIOD_VISUAL_FRAME, SIMCONNECT_DATA_REQUEST_FLAG_CHANGED | SIMCONNECT_DATA_REQUEST_FLAG_TAGGED);

I then just print the data to a command window.

Thanks
John.
 
Not all the simulation variables are calculated by FSX on each visual frame.

Since you set the SIMCONNECT_DATA_REQUEST_FLAG_CHANGED, which means you will be updated only when the variable has changed, you will not get any more updates than the update rate of that variable.

Which make sense: there's no need to request the value of a variable more frequently than its update interval.
 
Thanks so much for your reply Umberto!
So, if I wanted to build a gauge that somehow displayed the relative bearing of the current waypoint, similar to the GPS waypoint bearing needle on a HSI (G1000), what variable, or technique should I use? If I understand you correctly, I am ultimately limited by the FSX refresh rate for that particular variable, not how I am calling it. To make the updates smooth I would need a variable that refreshes much faster than the 1 sec that the GPS_WP_TRACK_ANGLE_ERROR seems to refresh at. I find it strange that such variables do not refresh much faster given they are used to make gauges - or am I mistaken that the GPS_WP_TRACK_ANGLE_ERROR would be used in that way?
Thanks again for your help!
John.
 
Well, the fact that a gauge tied to a variable moves smoothly, doesn't necessary mean the variable itself is smoothly updated!

With an XML Gauge, you could use the Delay objects to smooth out the actual indicator movement, even if the underlying variable "jumps" at every second. With C++/GDI+ it would be more complex, but is still doable, by filtering the readouts with a low-pass function.
 
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