libvxi11

MacOS and Linux C++ library for communicating with devices via the VXI-11 TCP/IP protocol

Eddie Lew, Lew Engineering, 1/21/2024

INTRODUCTION

This C++ library for Apple MacOS and Linux is used by applications to communicate with devices supporting the VXI-11 TCP/IP protocol.

This includes various test and measurement equipment that have an Ethernet port and labeled as LXI compliant. This library can also talk to LAN / GPIB gateways such as the Agilent E5810A or Keysight E5810B, allowing instruments with a GPIB (also known as HP-IB and IEEE-488) interface to be accessible on a local Ethernet network.

In fact, using an E5810A/B with this library is one of the easiest ways of talking to GPIB instruments on a Mac or a Linux PC, including the Raspberry Pi. No drivers are needed; simply link this library to your program. Also, since the E5810A/B is on your network, multiple computers can connect to multiple GPIB devices at the same time. And unlike USB GPIB interfaces, you are not tethered by a USB cable. You can control your GPIB instruments from any Mac or Linux computer anywhere in your lab.

The RPC protocol for VXI-11 is taken from the following document authored by the VXIbus Consortium, Inc.:

VMEBus Extensions for Instrumentation TCP/IP Instrument Protocol Specification VXI-11, Revision 1.0, July 17, 1995

The specification is included here in the VXI-11_Specification directory.

COMPILING

The library can be compiled from the command line on any Apple Macintosh computer with the Apple Xcode development tools installed, or from any Linux based PC or Raspberry Pi. Simply place all files of this project in a single directory and execute the following command:

make all

This will create libvxi11.1.dylib on MacOS and libvxi11.so.1 on Linux, which should be linked to your application with the -lvxi11 linker parameter.

The libvxi11.h file is the library's C++ header file.

To install the library to /usr/local/lib and /usr/local/include execute this command

make install

Depending on the permissions of /usr/local, you may need to run the following instead:

sudo make install

USAGE

Refer to libvxi11.h for a summary of the member functions available in the Vxi11 class. Refer to the function header comments in vxi11.cpp for a detailed description of how to use each member function.

Typical usage is as follows:

1. Instantiate the Vxi11 class. The constructor parameter indicates the hostname or IP address of the device to talk to. Create a separate object for each instrument you are talking to.

2. Reset the instrument with the clear() member function.

3. Send commands to the device via the write() or printf() member functions.

4. Read from the device via the read() member function.

5. For convenience, a query() member function does a write and read in one call.

6. When exiting your application, optionally call the local() member function to return the instrument to local front panel control and optionally call the close() member function to close the connection.

EXAMPLE

#include "libvxi11.h"
#include <stdio.h>

int main ()
{
  char s_msg[1000];

  // Example for an instrument with a built-in Ethernet port
  // "dmm6500" is the instrument hostname
  Vxi11 vxi11_dmm ("dmm6500");
  vxi11_dmm.clear ();                          // Reset the instrument
  vxi11_dmm.query ("*idn?", s_msg, 1000);      // Send ID query
  printf ("ID string = %s\n", s_msg);
  vxi11_dmm.printf (":sens:func \"volt:dc\""); // Select DC volts  
  double d_volts;
  vxi11_dmm.query (":read?", &d_volts);        // Do voltage measurement
  printf ("Volts = %f\n", d_volts);
  vxi11_dmm.local ();                          // Return to front-panel control

  // Example for a GPIB instrument connected to an LAN / GPIB gateway
  // "e5810a" below is the hostname of the gateway.  An IP address can also be
  // used.
  // "gpib0,25" indicates to talk to GPIB address 25
  Vxi11 vxi11_ps ("e5810a", "gpib0,25");
  vxi11_ps.clear ();                           // Reset the instrument
  vxi11_ps.query ("*idn?", s_msg, 1000);       // Send the ID query
  printf ("ID string = %s\n", s_msg);
  vxi11_ps.printf ("iset %f; vset %f", 0.25, 5.5); // Set current & voltage
  vxi11_ps.local ();                           // Return to front-panel control

  return (0);
}