The GtWave driver contains a set of functions for the GX11X0. Functions names that start with the GtWave prefix apply to all GtWave boards (i.e. GtWaveGetDriverSummary). The GtWave functions are designed with a consistent set of arguments and functionality. All boards have a function that initializes the GtWave driver for a specific board, resets the board, and displays the virtual panel. All the functions use handles to identify and reference a specific board and all functions return status and share the same functions to handle error codes.
The GtWave driver supports two device drivers HW and VISA which are used to initialize, identify and control the board. The user can use the GtWaveInitialize to initialize the board ‘s driver using HW and GtWaveInitializeVisa to initialize using VISA. The following describes the two different methods used to initialize:
Marvin Test Solutions' HW – This is the default device driver that is installed by the GtWave driver. To initialize and control the board using the HW use the GtWaveInitialize(nSlot, pnHandle, pnStatus) function. The function initializes the driver for the board at the specified PXI slot number (nSlot) and returns boards handle. The PXI/PCI Explorer applet in the Windows Control Panel displays the PXI slot assignments. You can specify the nSlot parameter in the following way:
A combination of chassis number (chassis # x 256) with the chassis slot number, e.g. 0x105 for chassis 1 and slot 5. The chassis number can be set by the PXI/PCI Explorer applet.
Legacy nSlot is used by earlier versions of HW/VISA. The slot number contains no chassis number and can be changed using the PXI/PCI Explorer applet: 23 in this example.
PXI/PCI Explorer
VISA – This is a third party library usually supplied by National Instruments (NI-VISA). You must ensure that the VISA installed supports PXI and PCI devices (not all VISA providers supports PXI/PCI). GtWave setup installs a VISA compatible driver for the GtWave board in-order to be recognized by the VISA provider. Use the GtWave function GtWaveInitializeVisa (szVisaResource, pnHandle, pnStatus) to initialize the driver’s board using VISA. The first argument szVisaResource is a string that is displayed by the VISA resource manager such as NI Measurement and Automation (NI_MAX). It is also displayed by MArvin Test Solutions PXI/PCI Explorer as shown in the prior figure. The VISA resource string can be specified in several ways as the following examples demonstrate:
Using chassis, slot: “PXI0::CHASSIS1::SLOT5”
Using the PCI Bus/Device combination: “PXI9::13::INSTR” (bus 9, device 9).
Using the alias: “ARB1”. Use the PXI/PCI Explorer to set the device alias.
Information about VISA is available at http://www.pxisa.org.
The GtWaveInitialize function returns a handle that is required by other driver functions in order to program the board. This handle is usually saved in the program as a global variable for later use when calling other functions. The initialize function does not change the state of the board or its settings.
The board handle argument, nHandle , is passed (by reference) to the parameter pnHandle of the GtWaveInitialize or the GtWaveInitializeVisa functions as a short integer (16 bits) number. It is used by the GtWave driver functions to identify the board being accessed by the application. Since the driver supports many boards at the same time, the nHandle argument is required to uniquely identify which board is being programmed.
The nHandle is created when the application calls the GtWaveInitialize function. There is no need to destroy the handle. Calling GtWaveInitialize with the same slot number will return the same handle.
Once the board is initialized the handle can be used with other functions to program the board.
The Reset function causes the driver to change all settings to their default state. The application software issue a Reset after the initializing the board, but a Reset can be issued at any time. All GX11X0 boards have the GtWaveReset(nHandle, nStatus) function. See the Function Reference section for more information regarding specific board functionality.
All GtWave functions pass a fail or success status – pnStatus – in the last parameter. A successful function call passes zero in the status parameter upon return. If the status is non-zero, then the function call fails. This parameter can be later used for error handling. When the status is error, the program can call the GtWaveGetErrorString function to return a string representing the error. The GtWaveGetErrorString reference contains possible error numbers and their associated error strings.
The GtWaveGetDriverSummary function can be used to return the current GtWave driver version. It can be used to differentiate between the driver versions. See the Function Reference section for more information.
Calling the GtWavePanel will display the instrument’s front panel dialog window. The panel can be used to initialize and control the board interactively. The panel function may be used by the application to allow the user to directly interact with the board.
The GtWavePanel function is also used by the GtWavePANEL.EXE panel program that is supplied with this package and provides a stand-alone Windows application that displays the instrument panel.