Data Acquisition Toolbox

Queuing Data with putdata

Before data can be sent to the analog output hardware, you must queue it in the engine. Queuing data is managed with the putdata function. One column of data is required for each channel contained by the analog output object. For example, to queue one second of data for each channel contained by the analog output object ao:

• ao = analogoutput('winsound');
  addchannel(ao,1:2);
  data = sin(linspace(0,2*pi*500,8000))';
  putdata(ao,[data data])
  

A data source consisting of m samples and n channels is illustrated below.

Rules for Using putdata

Using putdata to queue data in the engine follows these rules:

• You must queue data in the engine before starting the analog output object.
• If the value of the RepeatOutput property is greater than 0, then all queued data is automatically requeued until the RepeatOutput value is reached. You must configure RepeatOutput before start is issued.
• While the analog output object is running, you can continue to queue data unless RepeatOutput is greater than 0.
• You can queue data in the engine until the value specified by the MaxSamplesQueued property is reached, or the limitations of your hardware or computer are reached.

For more information about putdata, refer to its reference pages in Function Reference.

Rules for Queuing Data

Data to be queued in the engine follows these rules:

• Data is output as soon as a trigger occurs.
• An error is returned if a NaN is included in the data stream.
• You can use the native data type of the hardware. Note that MATLAB supports math operations only for the double data type. Therefore, to use math functions on native data, you must convert it to doubles.
• If the data is not within the range of the UnitsRange property, then it is clipped to the maximum or minimum value specified by UnitsRange. Refer to Linearly Scaling the Data: Engineering Units for more information about clipping.

Managing Output Data

Example: Queuing Data with putdata