This four-part series helps you transition from Traditional NI-DAQ (Legacy) to NI-DAQmx in the ANSI C and NI LabWindowsTM/CVITM programming languages.
NI is phasing out the Traditional NI-DAQ (Legacy) driver. The recommended new driver, NI-DAQmx, is designed for use with some of the newest data acquisition devices available from NI.
Refer to the “Traditional NI-DAQ (Legacy) Overview” and “NI-DAQmx Overview” sections for more information about the different available solutions.
This series references two manuals that are shipped with NI-DAQmx.
Traditional NI-DAQ (Legacy) is a library of routines that work with NI data acquisition (DAQ) devices. Traditional NI-DAQ (Legacy) helps you perform tasks ranging from simple device initialization to advanced high-speed data logging. The types of data acquisition devices and the complexity of your applications determine the number of tasks you need.
Traditional NI-DAQ (Legacy) is an older driver with outdated application programming interfaces (APIs) for developing data acquisition, instrumentation, and control applications for older NI DAQ devices. You should use Traditional NI-DAQ (Legacy) only in the following circumstances:
Refer to the NI-DAQ Readme file for more information about when to use Traditional NI-DAQ (Legacy), including a complete list of supported devices, operating systems, application software versions, and language versions.
In the following section, learn about the NI-DAQmx driver and the DAQmx ANSI C API as well as explore some of the advantages these provide over Traditional NI-DAQ (Legacy).
NI-DAQmx is the new NI data acquisition driver framework that addresses several weaknesses present in Traditional NI-DAQ (Legacy).
Some of the advantages of NI-DAQmx include:
Improved State Model
Consistent API across all Programming Languages
Robustness in Exceptional Conditions
Note: For additional information see Answers to Frequently Asked Questions about NI-DAQmx and Traditional NI-DAQ (Legacy).
The NI-DAQmx data acquisition framework introduces several new concepts, the two most important being tasks and task state models.
Learn how tasks are set up as you explore the NI-DAQmx ANSI C API in the following sections.
NI-DAQmx uses a task state model to improve ease of use and speed up driver performance. The task state model consists of five states – Unverified, Verified, Reserved, Committed, and Running.
You can choose to interact with as little or as much of the task state model as your application requires.
For more information about the NI-DAQmx task model, select NI-DAQmx Help»Key NI-DAQmx Concepts»Tasks»Task State Model in the NI-DAQmx Core Help.
The NI-DAQmx Core Help provides information about some of the other concepts of NI-DAQmx as well. For more information, select NI-DAQmx Help»Key NI-DAQmx Concepts.
The NI-DAQmx Core Help has flowcharts for each type of task. You can find these flowcharts under NI-DAQmx Help»Common Applications»Generic Programming Flows .
When framing a data acquisition application, regardless of the type of driver or device used for acquiring data, you organize the application into five main steps. The approaches to these five steps vary based on how the data acquisition driver is organized and the functionality it provides. These steps include the following:
1. Identify your measurement
2. Configure your measurement
3. Run the data acquisition operation
5. Clean up
These steps are the basic building blocks for creating a typical data acquisition application. You should be familiar with how a data acquisition application uses the NI-DAQ driver to address each of these steps and create an effective data acquisition application. Other documents in this series compare the NI-DAQmx ANSI C API with the Traditional NI-DAQ (Legacy) ANSI C API by breaking down their functionality into these five steps. Refer to the “Additional Resources” section to access these documents.
The DAQmx ANSI C API is available as part of the NI-DAQmx driver. Installing support for Microsoft Visual C Support installs the NI-DAQmx shipping examples and the API reference and concept documents. The ANSI C API is available for free as part of NI-DAQmx. LabWindowsTM/CVITM Support installs the examples and function panels.
ANSI C shipping examples for the NI-DAQmx C API are installed as part of the language support and are available under Start»All Programs»National Instruments»NI-DAQ»Text-Based Code Support»ANSI C Examples.
LabWindowsTM/CVITM examples can be found in the NI Example Finder under Hardware Input and Output»DAQmx .
The NI-DAQmx Quick Start Guide is a great document to get your data acquisition system up and running. It introduces setting up and installing NI DAQ devices on your machine and provides information about the various programming interfaces available for NI-DAQmx. For information about the programming interfaces and how to get started, refer to the “Getting Started Developing an Application” section in the NI-DAQmx Quick Start Guide. You can find the Quick Start Guide at Start»Programs»National Instruments»NI-DAQ»DAQ Quick Start Guide.
Before writing any code, you need to identify what kind of measurement you require.
Are you measuring temperature, strain, position, or another type of measurement? Are you using external sensors that need calibration or excitation? Will the sensor data require scaling of any kind? See DAQ Multifunction I/O Cable and Accessory Compatibility to select the correct cables and terminal blocks.
Once you have a good understanding of the type of measurement you are making, the next step is to configure the operation. Refer to “Transition from Traditional NI-DAQ (Legacy) to NI-DAQmx using ANSI C or LabWindowsTM/CVITM: Part II” for information on configuring your operation.
The mark LabWindows is used under a license from Microsoft Corporation.