Computer Control of Arbitrary Waveform Generator Based on LabVIEW Platform

Computer Control of Arbitrary Waveform Generator Based on LabVIEW Platform

Abstract: This paper introduces the computer control software of AFG320 arbitrary waveform generator designed and developed by using GPIB interface and virtual instrument development platform LabVIEW, which realizes computer control of AFG320 and expands the functions of AFG320.
Keywords: arbitrary waveform generator GPIB LabVIEW
Chinese Library Classification Number: TP123
Document Identification Code: B

1. Introduction
The rapid development of modern science and technology has put forward higher and higher requirements for test and measurement, which are mainly reflected in the aspects of multiple test tasks, high precision and high speed. For example, in the simulation test of the automobile cab, the traditional instrument manual operation and single-unit working mode can no longer meet its needs. The effective solution is to build an automatic test system. In order to integrate the currently widely used desktop arbitrary waveform generator instrument into the automatic test system, we designed a computer control software for the AFG320 arbitrary waveform generator of Tektronix. The advantages of this software are: user-friendly interface, simple operation, powerful functions and fast response. It not only realizes all local control of the instrument, but also realizes the functions of arbitrary waveform drawing, editing, storage, printing and output.
2. Computer control software design
AFG320 is a high-performance arbitrary waveform generator produced by Tektronix. It has the functions of generating, editing, storing and outputting standard waveforms/arbitrary waveforms. It is equipped with a GPIB interface, which can communicate with a computer or be controlled by a computer. For the GPIB interface card, we chose the AX5488 card of Axiomtek. This product uses the interface chip μPD7210 produced by NEC, which complies with the IEEE-488.2 standard and SCPI standard.
LabVIEW (Laboratory Virtual Instrument Engineering Workbench) is a virtual instrument development platform launched by National Instruments Corporation (NI). In this environment, LabVIEW replaces the text programming method of traditional programming language with a graphical language of icon connection, and users can flexibly design various applications. At the same time, LabVIEW provides a rich component library, function library and subroutine library, so that users can easily form the virtual test system they need. LabVIEW also provides DLL interface and CIN node, so that users can use modules compiled by other software platforms on the LabVIEW platform.
The AFG320 computer control software designed in this paper uses LabVIEW6.1 as the software development platform, which supports all functions of the instrument. After running, users can complete the waveform generation, storage, download and output functions without manual operation of the instrument. This software also provides a graphical waveform editing tool, allowing users to operate the mouse to draw and edit arbitrary waveforms for output. The AFG320 computer control software uses a large number of highly integrated standard program modules in the design and development project, including instrument initialization module, instrument management module, standard waveform selection and setting module, arbitrary waveform editing module, waveform modulation selection, setting and output module, waveform output module, etc. The output of standard waveform, special waveform and arbitrary waveform is realized by calling the waveform output module.
2.1 Software Flowchart
The software is designed with a concurrent structure, and the main program calls multiple subroutines at the same time. The main program flow of the software is shown in Figure 2.1.1 below.

Fig 2.1.1 Flow chart of software

2.2 Instrument Control Program
The instrument control program includes the instrument initialization module, instrument management module, waveform modulation selection, setting module and waveform output module.
Initialization module: performs instrument initialization, self-test and zeroing functions.
Instrument management module: performs instrument operation mode, locks and unlocks channels, restores factory settings and other instrument management operations.
Waveform modulation module: sets various modulation parameters and modulation waveforms such as SWP, FM, AM, FSK, etc.
Waveform output module: Since the instrument hardware can only recognize ASCII characters, this module converts the arbitrary waveform generated by user interaction, downloads it to the internal memory of the arbitrary waveform generator, and sends it to the instrument output channel to output the required waveform.
The above instrument control program is implemented by the main program calling the interface function in the GPIB.DLL dynamic link library provided by Axiomtek.
2.3 Arbitrary waveform editing module
This module uses three ways to generate arbitrary waveforms: function library editing, formula input and mouse drawing. The arbitrary waveform function library stores 23 function waveforms commonly used in production practice. Users can generate waveforms by simply selecting, modifying functions, and setting parameters such as waveform frequency and amplitude. The formula input method supports users to enter a formula to represent an arbitrary waveform. Users can also add special waveforms to the arbitrary waveform function library for storage. In order to facilitate users, we have also designed the function of drawing arbitrary waveforms with the mouse, as shown in Figure 2.3.1, which is the interface for drawing arbitrary waveforms with the mouse.

Fig 2.3.1 Interface of arbitrary waveform editing

When the user needs to draw an arbitrary waveform, first move the mouse to the moving cursor in the drawing area, then hold down the left mouse button and drag the mouse, and the moving trajectory of the mouse will form an arbitrary waveform. The user can also click the button below the drawing area to choose whether to draw an arbitrary curve or a straight line. The coordinates of the moving cursor can be known through the X and Y indicator values. The desired arbitrary waveform can also be accurately drawn by modifying the cursor coordinates. After the drawing is completed, click the stop button to return to the main interface, as shown in Figure 2.3.2. The user can use the editing tools provided to zoom in, zoom out, and translate the waveform, and can also set the waveform's color, position, whether it is adapted to the coordinate state, and other attributes.

Fig 2.3.2 Main interface

3. Conclusion
After module debugging and system joint debugging, the software is now running stably and normally. It enables the advanced function of AFG320 to output arbitrary waveforms to be flexibly applied, and realizes the arbitrary waveform drawing and editing functions that cannot be achieved by manually operating the instrument. Through the study of the computer control software of the AFG320 arbitrary waveform generator under the LabVIEW software platform, we have made a practical attempt on the development of virtual instruments, and the result is very successful.

References
[1]. Tektronix AFG320 Arbitrary Waveform Generator User Manual 1999
[2]. Yang Leping, Li Haitao, Xiao Xiangsheng, LabVIEW Programming and Application, Electronic Industry Press, 2001

Software for AFG320 Arbitrary Waveform Generator based on LabVIEW
Ding Xiaoliang　Pan lideng

Abstract: A control software based on the GPIB interface and LabVIEW for the AFG320 arbitrary waveform generator is described in this paper. The software realizes the computer control of AFG320, extends the functions of AFG320.
Keywords: Arbitrary Waveform Generator　GPIB　LabVIEW