Category: Knowledge Base SDM3000 Series

Many instruments include the ability to be controlled via a remote connection to a computer using an Ethernet connection. In many cases, these instruments require a special software library that can help establish and maintain the communications link between the instrument and controlling computer. This can be annoying for a few reasons… the software library is likely to occupy a large amount of space on the controlling computer and is also required on any computer that is being used to control the instrument. In a remote networking application where multiple user’s may want access to a test instrument, this can cause support and installation headaches.

Luckily, there are a few solutions that can help. In this application note, we are going to discuss using open socket communication techniques using an open source communication tool called PuTTY with a SIGLENT SSA3032X spectrum analyser.

What are open sockets and why use them?

Within the context of Ethernet/LAN connections, sockets are like mailboxes. If you want to deliver information to a specific place, you need to be sure that your information is delivered to the correct address.

In the context of test instrumentation, an open socket is a fixed address (or port number) on the Ethernet/LAN bus that is dedicated to process remote commands.

Open sockets allow remote computers to simply use existing raw Ethernet connections for communications without having to add additional libraries (VISA or similar) that require additional storage space and processing overhead.

Programs that utilize sockets for LAN communication tend to take up less memory and operate more quickly.

PuTTY

PuTTY is an open source software tool that provides a number of simple communication links (RAW, Telnet, SSSH, Serial, and others). It is available for free and there are a number of versions available for popular operating systems.

You can download as well as learn more here: https://www.putty.org/

In this example, we are using PuTTY to verify the raw LAN connection is working properly. It is quite a simple program that does not allow for very complex operation (sequences, converting data sets/strings, etc..). If you require more complex functionality, software platforms like Python, .NET, C#, LabVIEW, etc.. can be used to control the instrument using a similar open socket connection.

Configuration

In this test, we are using the most current revision of the SIGLENT SSA3032X Spectrum Analyzer firmware (Revision 01.02.08.02) which enables open socket communication.

This example also uses PuTTY version 0.67:

Steps

1. Install PuTTY for the OS you intend to use

2. Make sure your instrument and firmware revision can use open sockets

The SSA3032X revision 01.02.08.02 enables open socket communication.

To find the revision, press the System button > Sys Info.

Figure 1 below shows a sample system information screen from a SIGLENT SSA3000X analyzer:

Figure 1: Sample system information page from an SSA3000X.

Check the product page and firmware release notes for more information.

3. Connect the instrument to the local area using an Ethernet cable

4. Find the IP address for the instrument. This is typically located in the System Information menu. On the SIGLENT SSA3032X, press the System button on the front panel > Interface > LAN.

Figure 2 below shows a sample LAN setup page from a SIGLENT SSA3000X:

Figure 2: Sample LAN information page from an SSA3000X.

5. Open PuTTY

6. Select Raw as connection type

7. Enter the IP address in the Host Name field

8. Enter the port number. This should be provided in the users or programming guide for the instrument.

The SIGLENT SSA3000X uses port 5025.

Figure 3 below shows the PuTTY configuration for this example:

Figure 3: Example PuTTY configuration.

9. Press Open. This will open a terminal window as shown in below:

10. Using the computer keypad, enter *IDN? and press the Enter key on the keyboard to send the command.

This is the standard command string that is used to request the identification string from the instrument. As shown below, the instrument responds with the manufacture, product ID, Serial Number, and firmware revision.

Conclusion

PuTTY is an easy way to verify an operational LAN connection to instrumentation that can use open sockets.

Automating a test can dramatically increase the productivity, throughput, and accuracy of a process. Automating a setup involves connecting a computer to the test instrumentation using a standard communications bus like USB or LAN and then utilizing code entered via a software layer (like LabVIEW, .NET, Python, etc..) to sequence the specific instrument commands and process data.

This process normally goes quite smoothly, but if there are problems, there are some basic troubleshooting steps that can help get your test up-and-running quickly.

In this note, we are going to show how to use Telnet to test the communications connection between an instrument and a remote computer using a LAN connection to ensure that it is working properly. Once the connection is verified, you can begin to work on the control software.

Telnet provides a means of communicating over a LAN connection. The Telnet client, run on a LAN connected computer, will create a login session on the instrument.

NOTE: The Telnet connection requires open sockets on the instrumentation. At this time, not all SIGLENT products feature open sockets. Check the product page FAQs or with your local SIGLENT support office for more information.

A connection, established between the computer and instrument, generates a user interface display screen with SCPI> prompts on the command line.

Using the Telnet protocol to send commands to the instrument is similar to communicating with USB. You establish a connection with the instrument and then send or receive information using SCPI commands. Communication is interactive: one command at a time.

The Windows operating systems use a command prompt style interface for the Telnet client.

STEPS

1. Power on and connect the instrument to the network via LAN

2. Verify that the Gateway, Subnet Mask, and IP address of the instrument are valid for the network you wish to use. This information is typically located in the System Information or IO menu. See the specific instrument user’s guide for more information on LAN settings.

3. On the computer, click Start > All Programs > Accessories > Command Prompt.

4. At the command prompt, type in telnet.

5. Press the Enter key. The Telnet display screen will be displayed.

6. At the Telnet command line, type: open XXX.XXX.XXX.XXX 5024 where XXX.XXX.XXX.XXX is the instrument’s IP address and 5024 is the port. You should see a response similar to the following:

7. Now, you can enter any valid command for the specific instrument that you are controlling. See the specific programming guide for the instrument for more information.

This is especially helpful when you are planning a specific test sequence, the effect of delays/timing, or troubleshooting a command. You can send each command one-at-a-time and check the performance of the instrument.

*IDN? is a common identification string query (question or information request) that returns the information from the connected instrument

PyVISA is a software library that enables Python applications to communicate with resources (typically instruments) connected to a controlling computer using different buses, including: GPIB, RS-232, LAN, and USB.

This example scans and lists the available resources.

It requires PyVISA to be installed (see the PyVISA documentation for more information)

***

#Example that scans a computer for connected instruments that
#are compatible with the VISA communication protocol.
#
#The instrument VISA resource ID for each compatible instrument
#is then listed.
#
#
#Dependencies:
#Python 3.4 32 bit
#PyVisa 1.7
#
#Rev 1: 08302018 JC

import visa

def main():

rm = visa.ResourceManager()
print (rm.list_resources())

if __name__==’__main__’:

main()

*****

Here is the code:

And here is the result of a scan:

Each connected instrument returns a specific formatted string of characters called the VISA Resource ID.

The resource ID format is as follows:

‘Communication/Board Type (USB, GPIB, etc.)::Resource Information (Vendor ID, Product ID, Serial Number, IP address, etc..)::Resource Type’

In the response, each resource is separated by a comma. So, we have three resources listed in this example:

‘USB0::0x0483::0x7540::SPD3XGB4150080::INSTR’ – This is a power supply (SPD3X) connected via USB (USB0)

‘USB0::0xF4EC::0x1301::SVA1XEAX2R0073::INSTR’ – This is a vector network analyzer (SVA1X) connected via USB (USB0)

‘TCPIP0::192.168.55.122::inst0::INSTR’ – This is an instrument connected via LAN using a TCPIP connection at IP address 192.168.55.122