int Usbtmc_test() { /* This code demonstrates sending synchronous read & write commands */ /* to an USB Test & Measurement Class (USBTMC) instrument using */ /* NI-VISA */ /* The example writes the "*IDN?\n" string to all the USBTMC */ /* devices connected to the system and attempts to read back */ /* results using the write and read functions. */ /* The general flow of the code is */ /* Open Resource Manager */ /* Open VISA Session to an Instrument */ /* Write the Identification Query Using viPrintf */ /* Try to Read a Response With viScanf */ /* Close the VISA Session */ /***********************************************************/ ViSession defaultRM; ViSession instr; ViUInt32 numInstrs; ViFindList findList; ViStatus status; charinstrResourceString[VI_FIND_BUFLEN]; unsigned charbuffer[100]; int i; /** First we must call viOpenDefaultRM to get the manager * handle. We will store this handle in defaultRM.*/ status=viOpenDefaultRM (&defaultRM); if (status<VI_SUCCESS) { printf ("Could not open a session to the VISA Resource Manager!\n"); return status; } /* Find all the USB TMC VISA resources in our system and store the number of resources in the system in numInstrs. */ status = viFindRsrc (defaultRM, "USB?*INSTR", &findList, &numInstrs, instrResourceString); if (status<VI_SUCCESS) { printf ("An error occurred while finding resources.\nPress 'Enter' to continue."); fflush(stdin); getchar(); viClose (defaultRM); return status; } /** Now we will open VISA sessions to all USB TMC instruments. * 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 function panel by right clicking on the * descriptor parameter. After opening a session to the * device, we will get a handle to the instrument which we * will use in later VISA functions. The AccessMode and Timeout * parameters in this function are reserved for future * functionality. These two parameters are given the value VI_NULL.*/ for (i=0; i<int(numInstrs); i++) { if (i> 0) { viFindNext (findList, instrResourceString); } status = viOpen (defaultRM, instrResourceString, VI_NULL, VI_NULL, &instr); if (status<VI_SUCCESS) { printf ("Cannot open a session to the device %d.\n", i+1); continue; } /* * At this point we now have a session open to the USB TMC instrument. * We will now use the viPrintf function to send the device the string "*IDN?\n", * asking for the device's identification. */ char * cmmand ="*IDN?\n"; status = viPrintf (instr, cmmand); if (status<VI_SUCCESS) { printf ("Error writing to the device %d.\n", i+1); status = viClose (instr); continue; } /** Now we will attempt to read back a response from the device to * the identification query that was sent. We will use the viScanf * function to acquire the data. * After the data has been read the response is displayed.*/ status = viScanf(instr, "%t", buffer); if (status<VI_SUCCESS) { printf ("Error reading a response from the device %d.\n", i+1); } else { printf ("\nDevice %d: %s\n", i+1 , buffer); } status = viClose (instr); } /** Now we will close the session to the instrument using * viClose. This operation frees all system resources. */ status = viClose (defaultRM); printf("Press 'Enter' to exit."); fflush(stdin); getchar(); return 0; } int _tmain(int argc, _TCHAR* argv[]) { Usbtmc_test(); return 0; }解释代码