Example Code
以下範例程式碼是在 Microsoft Visual Studio 2022 中建立的，是跑在安裝 NI-VISA 的 Windows 系統上，它使用 GPIB-USB-HB+ 和 NI Instrument Simulator。
只需對程式碼稍作修改，就可以在 Linux 和其他 VISA 資源上執行。
/********************************************************************/
/* Simple Parse Resource Example */
/* */
/* This example demonstrates how you might test your system for */
/* the existence of a particular instrument. */
/* */
/* The general flow of the code is */
/* Open Resource Manager */
/* Use viParseRsrcEx() to test for the existence of a specific */
/* instrument */
/* Use viParseRsrc() to test for the existence of a specific */
/* instrument */
/* Open a session to this device */
/* Close the VISA Session */
/* */
/* This example works well with a NI Instrument Simulator on */
/* GPIB0::1::INSTR */
/********************************************************************/
#if defined(_MSC_VER) && !defined(_CRT_SECURE_NO_DEPRECATE)
/* Functions like strcpy are technically not secure because they do */
/* not contain a 'length'. But we disable this warning for the VISA */
/* examples since we never copy more than the actual buffer size. */
#define _CRT_SECURE_NO_DEPRECATE
#endif
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "visa.h"
static ViSession defaultRM;
static ViSession instr;
static ViStatus status;
static ViUInt32 retCount;
static ViUInt32 writeCount;
static char stringinput[512];
/*
* In every source code or header file that you use it is necessary to prototype
* your VISA variables at the beginning of the file. You need to declare the VISA
* session, VISA integers, VISA strings, VISA pointers, and VISA floating variables.
* Remember that if you are prototyping variables that are to be used as part of the
* VISA session that need this prototyping. As an example, above retCount has been
* prototyped as a static variable to this particular module. It is an integer of
* bit length 32. If you are uncertain how to declare your VISA prototypes refer
* to the VISA help under the Section titled Type Assignments Table. The VISA
* help is located in your NI-VISA directory or folder.
*/
int main(void)
{
/*
* First we must call viOpenDefaultRM to get the resource manager
* handle. We will store this handle in defaultRM.
*/
status = viOpenDefaultRM(&defaultRM);
if (status < VI_SUCCESS)
{
printf("viOpenDefaultRM: Could not open a session to the VISA Resource Manager!\n");
exit(EXIT_FAILURE);
}
else
{
printf("viOpenDefaultRM: Opened Session to the VISA Resource Manager.\n");
}
/*
* Now we will open a VISA session to a device at Primary Address 1.
* You can use any address for your instrument. In this example we are
* using GPIB Primary Address 1.
*
* We must use the handle from viOpenDefaultRM and we must
* also use a string that indicates which instrument to open. This
* is called the instrument descriptor. The format for this string
* can be found in the NI-VISA User Manual.
* After opening a session to the device, we will get a handle to
* the instrument which we will use in later VISA functions.
* The two parameters in this function which are left blank are
* reserved for future functionality. These two parameters are
* given the value VI_NULL.
*
* This example will also work for serial or VXI instruments by changing
* the instrument descriptor from GPIB0::2::INSTR to ASRL1::INSTR or
* VXI0::2::INSTR depending on the necessary descriptor for your
* instrument.
*/
ViRsrc cInstrString = "GPIB0::1::INSTR";
char cStatusChar[100] = "none";
ViPUInt16 intfType = 0; /* Interface type of the given resource string. */
ViPUInt16 intfNum = 0; /* Board number of the interface of the given resource string. */
ViChar rsrcClass[20] = "0";
ViChar expandedUnaliasedName[20] = "0";
ViChar aliasIfExists[20] = "0";
status = viParseRsrcEx(defaultRM, cInstrString, &intfType, &intfNum, rsrcClass, expandedUnaliasedName, aliasIfExists);
if (status < VI_SUCCESS)
{
printf("viParseRsrcEx of cInstrString[100] = \"GPIB0::1::INSTR\" before viOpen: Ressource not ready / existing.\n");
printf("--Error Code: %d \n", status);
viStatusDesc(&defaultRM, status, cStatusChar);
printf("--Error Code: %s \n", cStatusChar);
}
else
{
printf("viParseRsrcEx of cInstrString[100] = \"GPIB0::1::INSTR\" before viOpen: Ressource ready.\n");
}
status = viParseRsrc(defaultRM, cInstrString, &intfType, &intfNum);
if (status < VI_SUCCESS)
{
printf("viParseRsrc of cInstrString[100] = \"GPIB0::1::INSTR\" before viOpen: Ressource not ready / existing.\n");
printf("--Error Code: %d \n", status);
viStatusDesc(&defaultRM, status, cStatusChar);
printf("--Error Code: %s \n", cStatusChar);
}
else
{
printf("viParseRsrc of cInstrString[100] = \"GPIB0::1::INSTR\" before viOpen: Ressource ready.\n");
}
status = viOpen(defaultRM, cInstrString, VI_NULL, VI_NULL, &instr);
if (status < VI_SUCCESS)
{
printf("viOpen of cInstrString[100] = \"GPIB0::1::INSTR\": Cannot open a session to the device.\n");
printf("--Error Code: %d \n", status);
viStatusDesc(&defaultRM, status, cStatusChar);
printf("--Error Code: %s \n", cStatusChar);
goto Close;
}
else
{
printf("viOpen of cInstrString[100] = \"GPIB0::1::INSTR\": Opened session to the device.\n");
}
/*
* Now we will close the session to the instrument using
* viClose. This operation frees all system resources.
*/
Close:
printf("Closing Sessions\nHit enter to continue.");
fflush(stdin);
getchar();
status = viClose(instr);
status = viClose(defaultRM);
return 0;
}