144 lines
5.2 KiB
C
144 lines
5.2 KiB
C
/********************************************************************/
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/* Read and Write to a USBTMC Instrument */
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/* */
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/* This code demonstrates sending synchronous read & write commands */
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/* to an USB Test & Measurement Class (USBTMC) instrument using */
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/* NI-VISA */
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/* The example writes the "*IDN?\n" string to all the USBTMC */
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/* devices connected to the system and attempts to read back */
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/* results using the write and read functions. */
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/* */
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/* The general flow of the code is */
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/* Open Resource Manager */
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/* Open VISA Session to an Instrument */
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/* Write the Identification Query Using viWrite */
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/* Try to Read a Response With viRead */
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/* Close the VISA Session */
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/********************************************************************/
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#if defined(_MSC_VER) && !defined(_CRT_SECURE_NO_DEPRECATE)
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/* Functions like strcpy are technically not secure because they do */
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/* not contain a 'length'. But we disable this warning for the VISA */
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/* examples since we never copy more than the actual buffer size. */
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#define _CRT_SECURE_NO_DEPRECATE
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#endif
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include "visa.h"
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static ViSession defaultRM;
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static ViSession instr;
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static ViUInt32 numInstrs;
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static ViFindList findList;
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static ViUInt32 retCount;
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static ViUInt32 writeCount;
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static ViStatus status;
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static char instrResourceString[VI_FIND_BUFLEN];
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static unsigned char buffer[100];
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static char stringinput[512];
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int main(void)
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{
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int i;
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/*
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* First we must call viOpenDefaultRM to get the manager
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* handle. We will store this handle in defaultRM.
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*/
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status=viOpenDefaultRM (&defaultRM);
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if (status < VI_SUCCESS)
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{
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printf ("Could not open a session to the VISA Resource Manager!\n");
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exit (EXIT_FAILURE);
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}
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/* Find all the USB TMC VISA resources in our system and store the */
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/* number of resources in the system in numInstrs. */
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status = viFindRsrc (defaultRM, "USB?*INSTR", &findList, &numInstrs, instrResourceString);
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if (status < VI_SUCCESS)
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{
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printf ("An error occurred while finding resources.\nHit enter to continue.");
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fflush(stdin);
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getchar();
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viClose (defaultRM);
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return status;
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}
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/*
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* Now we will open VISA sessions to all USB TMC instruments.
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* We must use the handle from viOpenDefaultRM and we must
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* also use a string that indicates which instrument to open. This
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* is called the instrument descriptor. The format for this string
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* can be found in the function panel by right clicking on the
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* descriptor parameter. After opening a session to the
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* device, we will get a handle to the instrument which we
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* will use in later VISA functions. The AccessMode and Timeout
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* parameters in this function are reserved for future
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* functionality. These two parameters are given the value VI_NULL.
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*/
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for (i=0; i<numInstrs; i++)
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{
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if (i > 0)
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viFindNext (findList, instrResourceString);
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status = viOpen (defaultRM, instrResourceString, VI_NULL, VI_NULL, &instr);
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if (status < VI_SUCCESS)
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{
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printf ("Cannot open a session to the device %d.\n", i+1);
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continue;
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}
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/*
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* At this point we now have a session open to the USB TMC instrument.
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* We will now use the viWrite function to send the device the string "*IDN?\n",
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* asking for the device's identification.
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*/
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strcpy (stringinput,"*IDN?\n");
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status = viWrite (instr, (ViBuf)stringinput, (ViUInt32)strlen(stringinput), &writeCount);
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if (status < VI_SUCCESS)
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{
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printf ("Error writing to the device %d.\n", i+1);
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status = viClose (instr);
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continue;
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}
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/*
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* Now we will attempt to read back a response from the device to
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* the identification query that was sent. We will use the viRead
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* function to acquire the data. We will try to read back 100 bytes.
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* This function will stop reading if it finds the termination character
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* before it reads 100 bytes.
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* After the data has been read the response is displayed.
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*/
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status = viRead (instr, buffer, 100, &retCount);
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if (status < VI_SUCCESS)
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{
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printf ("Error reading a response from the device %d.\n", i+1);
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}
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else
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{
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printf ("\nDevice %d: %*s\n", i+1, retCount, buffer);
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}
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status = viClose (instr);
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}
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/*
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* Now we will close the session to the instrument using
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* viClose. This operation frees all system resources.
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*/
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status = viClose (defaultRM);
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printf ("Hit enter to continue.");
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fflush (stdin);
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getchar();
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return 0;
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}
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