Data Acquisition Toolbox

Evaluating the Analog Output Object Status

You can evaluate the status of an analog output (AO) object by

• Returning the values of certain properties
• Invoking the display summary

Status Properties

The properties associated with the status of your analog output object allow you to evaluate

• If the device object is running
• If data is being output from the engine
• How much data is queued in the engine
• How much data has been output from the engine

These properties are given below.

Table 6-5: Analog Output Status Properties

Property Name	Description
Running	Indicate if the device object is running.
SamplesAvailable	Indicate the number of samples available per channel in the engine.
SamplesOutput	Indicate the number of samples output per channel from the engine.
Sending	Indicate if data is being sent (output) to the hardware device.

When data is queued in the engine, SamplesAvailable is updated to reflect the total number of samples per channel that was queued. When start is issued, Running is automatically set to On.

When the trigger executes, Sending is automatically set to On and SamplesOutput keeps a running count of the total number of samples per channel output from the engine to the hardware. Additionally, SamplesAvailable tells you how many samples per channel are still queued in the engine and ready to be output to the hardware.

When all the queued data is output from the engine, both Running and Sending are automatically set to Off, SamplesAvailable is 0, and SamplesOutput reflects the total number of samples per channel that was output.

The Display Summary

You can invoke the display summary by typing an AO object or a channel object at the MATLAB command line, or by excluding the semicolon when

• Creating an AO object
• Adding channels
• Configuring property values using the dot notation

You can also display summary information via the Workspace browser by right-clicking a toolbox object and selecting Explore -> Display Summary from the context menu.

The information displayed reflects many of the basic setup properties described in Configuring Analog Output Properties, and is designed so you can quickly evaluate the status of your data acquisition session. The display is divided into two main sections: general summary information and channel summary information.

General Summary Information

The general display summary includes the device object type and the hardware device name, followed by this information:

• Output parameters -- The sampling rate
• Trigger parameters -- The trigger type
• The engine status
• Whether the engine is sending data, waiting to start, or waiting to trigger
• The total time required to output the queued data
• The number of samples queued by putdata
• The number of samples sent to the hardware device

Channel Summary Information

The channel display summary includes property values associated with

• The hardware channel mapping
• The channel name
• The engineering units

The display summary shown below is for the example given in Outputting Data with a Sound Card prior to issuing the start function.

You can use the Channel property to display only the channel summary information.

• AO.Channel
  

Analog Output Examples

Managing Output Data