Introduction

When developing an application to control LeCroy oscilloscopes via the LAN interface, we recommend using either our VICP Client Library or our VICP Passport to help manage TCP/IP communications. This application note answers many questions frequently asked about VICP and the VICP Passport. For additional information, contact your local LeCroy Applications Engineer.

 

  1. Why does LeCroy have its own NI-VISA Passport?

    LeCroy developed the VICP Passport so that users of NI-VISA could have more reliable communications with LeCroy scopes when using the LAN interface. We found that the code written by 3rd parties to parse and decode the instrument response (which includes an 8-byte header including 8 "operation" bits") was not 100% reliable. One example of unreliability was dealing with unread responses; the VICP Passport handles this properly.

  2. What is VICP?

    VICP is LeCroy's Versatile Instrument Control Protocol. When LeCroy came out with it's first LANbased instrument (circa 1997), a protocol was needed that established a specific port for communications between the client controlling the scope and the instrument that serves up the data. The port for VICP is 1861; this port number is officially registered with IANA, which is an operating unit of ICANN, (see http://www.iana.org/assignments/port-numbers). The protocol also defines a communications format including a header with a byte that describes the state of the instrument of the data transfer. See the remote control manual for your oscilloscope for details about the VICP header.

  3. What is NI-VISA?

    NI-VISA is National Instrument's implementation of the VISA standard. VISA is the Virtual Instrument Software Architecture, a standard managed by the IVI Foundation (http://www.ivifoundation.org). VISA defines a software layer that allows users to control instruments without needing to understand the workings of interface bus being used. For more information, go to http://www.ni.com/VISA.

  4. What is a VISA Passport?

    A passport is a plug-in library module that handles the communications with a class of instruments. NI-VISA includes passports for GPIB, serial, TCPIP, FireWire, USB, etc. The passports visible to your installation of NI-VISA can be found in the VISA Options section of National Instrument’s Measurement and Automation Explorer application. (See figure 1). After installation, the VICP Passport will be included in this list as well.

  5. Is the code to interpret VICP available?

    Code to parse VICP packets (the LeCroy VICP Client Library) is publicly available at http://www.SourceForge.net.

  6. What is the difference between VICP and VICP Passport?

    VICP is the protocol for communicating with LeCroy oscilloscopes over TCP/IP; the VICP Passport is a National Instruments sanctioned plug-in to NI-VISA for communicating with the LeCroy instruments via TCP/IP using the NI-VISA library of functions.

  7. I used to communicate with older LeCroy scope without using the VICP Passport. What should I be using now?

    Note that the VICP Passport is only associated with NI-VISA. (It sits under the NI-VISA “umbrella”.) If you are using NI-VISA, we recommend installing the VICP Passport on your client PC for the reasons described in #1 above. As of this date (Feb 2007), all LeCroy scopes (both current and obsolete) that utilize a TCP/IP interface are compatible with the VICP passport. If you are not using NI-VISA, we recommend using the code in the LeCroy VICP Client Library available at http://www.SourceForge.net.

    Figure 1:

    National Instruments’ Measurement and Automation Explorer application displaying the list of VISA Passports. The LeCroy VICP Passport is at the top of the list.

  8. Will using the VISA address string "TCPIP0::<ip address>::1861::SOCKET" work?

    Maybe, depending on how your application handles instrument responses. When using this address string, it is up to the user to be sure that their application handles the responses correctly. The data returned when using this address string will include header information that needs to be parsed, and allowances must be made to trap situations where a transfer is not complete, or where there is an unread response from the instrument. This is not simple to do, and we have found that various drivers have not been as reliable as we would have liked them to be. LeCroy has solved these problems with the VICP Passport.

  9. Is the VICP Passport a "Standard"?

    It is not a standard - it's a piece of software for managing communications with your scope. The VICP Passport is 100% sanctioned and supported by LeCroy and National Instruments.

  10. How do I use the VICP Passport?

    Download the passport from http://www.lecroy.com (it’s in the Software Utilities section of the website), and install it on client PCs that will be used to control your LeCroy oscilloscope. To connect to your instrument, open the connection using the VISA Open function using an address string taking the form VICP::<ip address> or VICP::<hostname> (e.g. VICP::123.45.67.8). You can use the hostname syntax if you are connected to a nameserver. The more formal syntax is VICP::<ip address>::INSTR and VICP::<hostname>::INSTR, but the ::INSTR suffix is usually not required. Most instrument drivers will have an Initialize function with an argument to receive the resource name formatted as a string.

  11. What about GPIB communications?

    GPIB connections are not handled at all by VICP or VICP Passport. NIVISA users communicating via GPIB should continue to use the GPIB::<ip address>::INSTR address string.

  12. So in summary, what does using the VICP Passport do for me?

    The VICP Passport gives you the ability to communicate with a networked LeCroy scope using the NIVISA interface, while hiding the details of LeCroy's VICP protocol layer.