usb-6009
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159
NI-VISA/Examples/C/Serial/RdWrtSrl.c
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159
NI-VISA/Examples/C/Serial/RdWrtSrl.c
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/********************************************************************/
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/* Read and Write to a Serial Instrument */
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/* */
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/* This code demonstrates sending synchronous read & write commands */
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/* through the serial port using VISA. */
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/* The example writes the "*IDN?\n" string to the serial port (COM1)*/
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/* and attempts to read back a result using the write and read */
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/* 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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/* Configure the Serial Port */
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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 retCount;
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static ViUInt32 writeCount;
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static ViStatus status;
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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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/*
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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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/*
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* Now we will open a VISA session to the serial port (COM1).
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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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status = viOpen (defaultRM, "ASRL1::INSTR", 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.\n");
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goto Close;
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}
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/*
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* At this point we now have a session open to the serial instrument.
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* Now we need to configure the serial port:
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*/
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/* Set the timeout to 5 seconds (5000 milliseconds). */
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status = viSetAttribute (instr, VI_ATTR_TMO_VALUE, 5000);
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/* Set the baud rate to 4800 (default is 9600). */
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status = viSetAttribute (instr, VI_ATTR_ASRL_BAUD, 4800);
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/* Set the number of data bits contained in each frame (from 5 to 8).
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* The data bits for each frame are located in the low-order bits of
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* every byte stored in memory.
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*/
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status = viSetAttribute (instr, VI_ATTR_ASRL_DATA_BITS, 8);
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/* Specify parity. Options:
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* VI_ASRL_PAR_NONE - No parity bit exists,
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* VI_ASRL_PAR_ODD - Odd parity should be used,
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* VI_ASRL_PAR_EVEN - Even parity should be used,
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* VI_ASRL_PAR_MARK - Parity bit exists and is always 1,
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* VI_ASRL_PAR_SPACE - Parity bit exists and is always 0.
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*/
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status = viSetAttribute (instr, VI_ATTR_ASRL_PARITY, VI_ASRL_PAR_NONE);
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/* Specify stop bit. Options:
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* VI_ASRL_STOP_ONE - 1 stop bit is used per frame,
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* VI_ASRL_STOP_ONE_5 - 1.5 stop bits are used per frame,
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* VI_ASRL_STOP_TWO - 2 stop bits are used per frame.
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*/
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status = viSetAttribute (instr, VI_ATTR_ASRL_STOP_BITS, VI_ASRL_STOP_ONE);
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/* Specify that the read operation should terminate when a termination
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* character is received.
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*/
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status = viSetAttribute (instr, VI_ATTR_TERMCHAR_EN, VI_TRUE);
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/* Set the termination character to 0xA
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*/
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status = viSetAttribute (instr, VI_ATTR_TERMCHAR, 0xA);
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/* We will 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.\n");
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goto Close;
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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.\n");
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}
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else
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{
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printf ("\nData read: %*s\n", retCount, buffer);
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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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Close:
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status = viClose (instr);
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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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