USB-6211 clocked DA generates error

[mhubel]

We are using the DAQmx library called by a C program. Part of the application is to drive the D-A on the device at a clocked rate (1 to 10 KHz). The problem call is:

    DAQmxErrChk (DAQmxCfgSampClkTiming(DAtaskHandle,
        "",    //source (default to OnboardClock)
        5000,    //rate in samples per second
        DAQmx_Val_Rising,    //active edge
        DAQmx_Val_ContSamps,    //Continuous sampling
        600    //samples to send
        ));

and it returns the error:

Non-buffered hardware-timed operations are not supported for this device and Channel Type.

The mode DAQmx_Val_HWTimedSinglePoint has also been tried without success. As the USB-6211 claims in the specs to be capable of sending D-A values out at up to a 250 KHz rate, there must be something like this which works. Any suggestions?

[mhubel]

Found a solution. It seems the default buffer size is 0 so the buffer must be configured. The following sequence works:

    DAQmxErrChk (DAQmxCreateAOVoltageChan(DAtaskHandle,
        devcmd,    //physical channel
        "",    //name assigned
        0.0,    //min output value
        5.0,    //max output value
        DAQmx_Val_Volts,    //units of output
        ""    //custom scale name
        ));
    DAQmxErrChk (DAQmxCfgOutputBuffer (DAtaskHandle, 600));    //set buffer size to 600
    DAQmxErrChk (DAQmxCfgSampClkTiming(DAtaskHandle,
        "",    //source (default to OnboardClock)
        5000,    //rate in samples per second
        DAQmx_Val_Rising,    //active edge
        DAQmx_Val_ContSamps,    //Continuous sampling    DAQmx_Val_HWTimedSinglePoint,
        600    //samples to send
        ));
    DAQmxErrChk (DAQmxWriteAnalogF64(DAtaskHandle,
        600,    //samples per channel
        1,    //auto start
        10.0,    //timeout in seconds
        DAQmx_Val_GroupByChannel,    //data layout
        data,    //data to output
        NULL,    //samples written
        NULL    //reserved
        ));