VDT commands and background tasks

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I constantly read out data via serial line & VDT2 in a background task (with an update speed of 60 ticks). I want to read several (5 or more) values from a device like:

Function ReadInBackground(s)
    STRUCT BackStruct &s
   
    String Response
    Variable i
    for (i = 0; i < NumberOfCommands; i += 1)
        VDTWrite2 StringFromList(i, ListOfCommands)+"\r"
        VDTRead2/Q/O=0.5 Response
        if(V_VDT == 0)
            // do timeout handling
            return 0
        endif
        SomeValueWave[i] = str2num(Response)
    endfor
    return 0
End


But this is soooo slow and leads to hiccups of Igor every time the process executes. Unfortunately the device doesn't accept more than one command before a readout (or I have't found out yet). I wonder if there is a way to optimize and speed up the whole thing.
It might be sufficient to just set the timeout time to a smaller value like 0.01.

If that does not work, in your background task, use:
VDTGetStatus2 0, 0, 0


This sets the variable V_VDT to the number of characters in the input buffer. If the number of characters is big enough, call VDTRead2 to read one number. If not, just return from the background task.

August 18, 2010 at 12:00 pm - Permalink