While the previous sections all looked at using the oscilloscope interactively, many users expect to use test equipment via remote control or as part of an integrated testing solution. Fortunately, the Rohde & Schwarz RTM3004 offers a USB device port and an Ethernet port for PC or LAN connectivity.
Setup of the RTM3004’s connectivity is done through the on-screen menu. The unit is capable of either USB connectivity or LAN connectivity, but not both at the same time. If USB is selected, the unit can be toggled through three different modes – USB MTP, USB VCP and USB TMC. If Ethernet is selected, configuration of the instrument’s IP address, port, hostname and password can be configured. Other than that, it’s as simple as ensuring the cable is plugged in.
Installation of software is optional depending on how you are using the instrument. Rohde & Schwarz provides RSCommander for remote control, R&S RTx Report Creator for creating power analysis reports and drivers for IVI.NET, LabVIEW and VXIpnp.
As embedded/internet-of-things devices start to permeate our networks, in recent times, there has been an increased focus on network security. While in general, LAN-connected instruments are not recommended for connection to the public internet or untrusted networks due to the presence of “simple” unauthenticated protocols which can alter the operation of the instrument (e.g. SCPI direct on Port 5025), it is still worth checking what services are offered by the device.
After a quick port-scan, it seems that the RTM3004 has the following ports open:
- 80/tcp (HTTP)
- 111/tcp (rpcbind?)
- 1024/tcp (VXI-11)
- 1025/tcp (NFS?)
- 5025/tcp (SCPI)
- 111/udp (rpcbind?)
While ports 80, 1024 and 5025 are expected due to the feature-set offered by the RTM3004, the findings of port 111 and 1025 were a little unexpected. The use of unencrypted HTTP is acceptable for use inside a local trusted network but may be vulnerable to sniffing and session hijacking.
It was also discovered that outside ordinary operation, certain packets or packet sequences can cause the unit to stop responding, requiring a reboot from the front panel with no other perceived side effects. This has been reported to Rohde & Schwarz for investigation and rectification.
Web Browser (LAN)
The simplest way of getting started is to use the LAN interface and hook it up to your network. Plugging the IP address into a web browser allows you to access the instrument. From this main screen, you can change languages, see the status of the instrument, use the “identify” feature to find the instrument by showing a message on the display and move through several other screens that allow you to reconfigure and remotely interact with the instrument.
The Screenshot page displays a screen image, allowing you to toggle some settings and have limited control of the oscilloscope. This may be useful for more basic browsers which might not be compatible with the more advanced features.
SCPI Device Control allows you to send single commands and read responses – nothing too special here.
Save/Load allows you to save or load data to or from your computer to the oscilloscope’s memory or connected storage.
Network Settings allows you to reconfigure the RTM3004 Network Settings remotely. This is useful, but if you get something wrong, the unit may become unreachable until the settings are corrected using the front panel.
Change Password allows you to change the access password for the web browser interface.
Having a password on the interface is quite useful as it stops any passer-by from being able to manipulate your instrument without first keying in the password. The protection is, however, quite weak as the connection is plain HTTP and other ports are available on the instrument for direct access.
Livescreen provides a self-refreshing remote view of the screen without any control features. This is particularly useful if you just want to see the image remotely without clutter on the side or the risk of accidentally remote-controlling the instrument (e.g. for education to project onto the screen in an auditorium). The performance is quite good, as this 3-second-looped GIF shows (noting this is “at home” via software screen capture on Firefox – it could be even faster depending on the browser/computer).
The pièce de résistance, however, is the Remote Front Panel. This feature works extremely well and allows browser-based remote access to everything – you click in the screen, it acts if you’ve physically touched the screen. Drags, keyboard input and even rotating the virtual knobs are all faithfully relayed to the instrument. It is an absolute joy to use.
In fact, you can even connect to it from your smartphone just to start an operation – I was doing it from the comfort of my bed, wirelessly, on a frosty cold morning … a new way to use an oscilloscope?
The advantages of the LAN interface are numerous – fast access, use without any specialised drivers or software, the ability to share the instrument across different computers, across further distances, even wirelessly to mobile devices. Almost everything that can be done with the instrument without physically plugging or unplugging something can be done this way. It worked relatively flawlessly in normal operation and I find this to be my preferred method of connection, although there may be instances for pure throughput, security or latency requirements where USB is preferable.
USB MTP Interface
The default USB interface selection appears to be Media Transfer Protocol (MTP), which turns the RTM3004 into something more like a smartphone connected via USB. This does not require any driver installation and is detected as a “Portable Device”. The device has a VID of 0AAD and PID of 01D7.
The device can be browsed through the file manager, exposing three different folders – Internal Storage, Live Data and Upload.
Internal Storage provides access to the data in the internal storage of the RTM3004, arranged as shown in the folder listing below.
Live Data is a virtualised filesystem with many files having a “dummy” size, allowing you to copy or view the files which are then live generated on request.
Finally, the Upload folder seems to be used to send data to the RTM3004 and is otherwise empty except for an explanatory document.
This is a rather interesting alternative way of using USB to allow for access to the oscilloscope data, but is rather limited, as it doesn’t have any capability for remote control via SCPI commands. Other than via LAN, only the USB VCP and USB TMC interfaces offer this possibility. In those modes, MTP access is not possible.
USB VCP Interface
The USB Virtual COM Port (VCP) interface is a simplified way of being able to communicate with the instrument over USB. This presents a USB COM port based on the USB CDC class, similarly to how a USB to TTL UART adapter would work, thus meaning that communicating with the instrument is as simple as sending SCPI commands through to a COM port.
The device is recognised under Windows 10 with no additional drivers required, using a VID of 0AAD and PID of 013C.
I sent the basic *IDN? Command over using the Arduino IDE’s serial monitor and confirmed that this works, making it a good simple option for those who don’t want to bother with working with VISA libraries.
USB TMC Interface
When USB TMC is selected, the device is detected as an USB Test and Measurement Device (IVI) with a VID of 0AAD and PID of 01D6. To use this device requires going through the installed VISA stack.
The RSCommander installation process was rather straightforward. Depending on the interface, in order to get it to work, you might need also to install a supported VISA library (e.g. R&S Visa), various IVI and IVI.NET Shared Components and the drivers provided by Rohde & Schwarz. In my case, it seems that getting it to work over Ethernet was the simplest and it seemed to operate properly even using NI-VISA.
RSCommander provides the ability to take screenshots and save/print a hardcopy. By default, it seems to change your screenshot settings to monochrome.
It also allows for plotting and saving of the raw trace data rather than looking at the screenshot. This is easier than
File upload and download is supported.
One powerful feature is the Scripts feature which allows you to do some automation using Python using PyVISA.
Finally, there is the IControl window which provides basic SCPI command sending and receiving.
While RSCommander is quite basic and mostly offers features which can be more easily accessed via the Web Interface, the trace data saving and script feature can be handy especially for those who don’t have more fully-featured test lab automation software.
R&S RTx Report Creator
Installing the R&S RTx Report Creator was slightly less straightforward, as it seems that you need to manually run the installation program as administrator as it doesn’t request elevated privileges automatically and balks when copying the files to the target directory.
The software appears to be used to create PDF power analysis reports from data stored by the oscilloscope when using the RTM-K31 Power Analysis option.
The software has features to customise the layout and content of these reports. However, as mentioned previously in the Power Analysis chapter, the RTM-K31 option is intended for use with Rohde & Schwarz’s specialised active high-voltage/current probes and deskew fixtures and as such, I didn’t save any report data for testing the report creator with.
When it comes to remote operation, the RTM3004 was extremely impressive, offering a wide array of flexible choices when it comes to interfacing, communicating and controlling the unit. The LAN interface impressed with a browser-based interface that catered for changes in configuration, SCPI command execution, file upload/download, had basic password protection and a high-performance remote front panel and screen capture facilities. The faithfulness of the remote front panel in responding to browser-based touch, drag, keyboard input, virtual knob and button made it a pleasure to use and an excellent choice if you need to duplicate the display (e.g. for educational purposes to project into an auditorium). This worked reliably even from a smartphone over Wi-Fi.
Where LAN is not suitable, three USB modes are provided. USB MTP allows for driverless file-based operations, allowing for download and upload of files but also accessing “live data” which is generated on request. This is at the expense of SCPI command support. USB VCP presents a CDC-based COM port, simplifying application development, allowing raw SCPI commands and responses to be transferred over a virtual COM port. Finally, USB TMC presents a familiar IVI interface for use with VISA libraries.
The instrument is provided with IVI.COM, LabView and VxIPnP drivers. Further to this, it is provided with the RSCommander software which provides similar functionality but also adds the ability to automate operations using a Python-based PyVISA script facility. The R&S RTx Report Creator also allows for the creation of PDF reports from recorded report data from the RTM-K31 Power Analysis option.
The only minor issue appears to be the LAN interface locking up the unit when an unusual packet sequence is received which was reported to Rohde & Schwarz for rectification in a firmware update.