As the last blog post concentrated on the usage of the MSO on-the-bench, this one will focus on its capabilities when using its remote-control interfaces.
Documentation and Support
Information regarding the 2-series MSO’s programmatic interface is available in the form of a programmer’s manual. The manual is 791 pages long and details the commands available through the remote interfaces. I found it comprehensive and accurate, although the structure of the commands was a little unexpected at times. I rarely automate oscilloscopes, but I did note that some status calls return large “blobs” of text which is a mixture of human-readable mixed with numeric values, rather than having a separate specific command to query a given status condition. As a result, the command set seems to have fewer commands, in exchange for the programmer needing to do a bit more work to extract the information from the response. Another thing I noticed was the lack of a SYSTem subsystem, which is unusual, as I’m used to querying SYSTem:ERRor?
Code examples for oscilloscopes are also available on Tektronix’s GitHub at https://github.com/tektronix/Programmatic-Control-Examples/tree/master/Examples/Oscilloscopes, although there are no examples for the 2-series MSO specifically.
The oscilloscope is also supported by the TekSeriesScope IVI-COM drivers which can be downloaded from Tektronix’s website. A number of Tektronix proprietary applications are also available that will work with the oscilloscope – this will be detailed in the following chapter.
USB Host
On the side of the MSO24 is two USB 2.0 host ports. These host ports can support the connection of USB mass storage devices (e.g. USB flash drives) for data storage and transfer. I did test with a number of USB 2.0 and USB 3.0 drives and external SSDs with no issues. It appears to support FAT, FAT32, NTFS, exFAT but it only seems to be able to mount the first partition on any given device. I did try to get it to mount some ext2/3/4 formatted drives as it is running Linux, but it appears that it doesn’t attempt to mount such partitions.
If you don’t particularly get along with the touch-screen interface, you can also attach a USB keyboard and USB mouse. I tried this with a Dell KB522p USB keyboard and Logitech M100 USB mouse and had no issues. In fact, it did make it easier to better define masks in mask testing. I also found the hub on the USB keyboard to work just fine, allowing the two ports on the MSO to stretch further.
In theory, such ports can be used for other devices (e.g. USB Wi-Fi adapters) although no such features have been advertised. I did try a few Wi-Fi adapters in my possession (based around Realtek, Ralink/Mediatek, Atheros chipsets known to work in Linux) but didn’t see any changes to the UI that would suggest it is supported. Maybe this is something that could change, as some other models of Tektronix oscilloscope do support the use of USB Wi-Fi adapters (even if they are a less reliable option than inbuilt Wi-Fi or an Ethernet cable).
USB Device
The MSO24 has a single USB2.0 device port which is used for remote control via its SCPI-based programmatic interface. The device port can be enabled or disabled via the I/O settings page.
Once enabled, plugging the MSO24 into a computer should have it detect and install the universal IVI driver (assuming a compatible VISA layer is already installed).
Once installed, the device can be accessed using VISA in the same way most SCPI-enabled instruments can.
Ethernet/LAN
A common and convenient way to connect instruments for remote control is via Ethernet to a local area network (LAN). The MSO24 supports gigabit Ethernet connectivity with IPv4 addressing. The oscilloscope does have some “connected scope” features which rely on this connectivity. I did opt to disable usage tracking.
Unfortunately, the availability of Ethernet is not a given in all places. It would have been nice to see Wi-Fi being available, so that connected features (e.g. network storage, TekDrive, remote control) could be used in spite of this (e.g. via connecting to a mobile phone tethering hotspot).
As with most network devices, it is almost plug-and-play, with the device acquiring an address via DHCP automatically. Various capabilities can be enabled or disabled through the I/O settings.
For example, SCPI commands can be sent to port 4000 socket server, depending on the setting of this toggle.
Device Detection
Most instruments I meet can be automatically detected on the network through mDNS, however, this instrument seems to be an exception. By default, opening NI MAX doesn’t list the MSO24 on the network at all.
I had to manually scan the network for instruments before the MSO24 was detected and added (manually) to the list of devices.
This is perhaps not as user friendly as detection through mDNS and does result in some instances (after rebooting the computer) of the instrument not being automatically detected until the VISA layer is forced to refresh and rescan the instruments on the network.
After manually adding it to the system, it does function correctly. This remote control interface was used extensively in performing the input error and AWG error measurements as part of the Instrument Performance Tests chapter of this review.
VNC Server
For remote control of the oscilloscope of the “remote screen, keyboard and mouse” variety, the MSO24 supports the VNC protocol. By default, VNC is disabled and when enabled, a password can be set but will only take effect after a reboot of the instrument.
This server proved useful in making some of the screenshots in this review. Its performance was quite good, reaching approximately 15fps (although this varies with the complexity of the displayed image). The performance is demonstrated in the below animated GIF image.
One downside of the VNC server is the lack of access to the front panel buttons and knobs. Some operations are difficult or impossible to do efficiently without this access (or knowing the relevant SCPI commands and issuing them directly to the socket server port).
Web Interface
Most Ethernet LAN-enabled instruments have a web-based interface of some sort that can be used to verify connection information and issue remote-control commands. Some even allow you to access and control the instrument remotely via a web browser.
Unfortunately, for the 2-series MSO, there is no web interface to speak of. On the higher-end 3-series MDO and above, the web interface is known as e*Scope, however, referring to Tek’s webpage on this feature, the 2-series is notably absent. This was not expected given the visual similarities in the UIs – I had naturally assumed it would have inherited this feature.
Open Ports
I did a quick check of the open ports on the device using nmap. Nothing particularly noteworthy was found, although it is clear we are dealing with a Tektronix instrument (port 4000 instead of the more common 5025 for SCPI remote control). The ephemeral ports appear to change, while the MSO24 does seem to lock-up after hours of being scanned, thus isn't entirely robust to repeated malformed requests.
PORT STATE SERVICE VERSION 111/tcp open rpcbind 2-4 (RPC #100000) | rpcinfo: | program version port/proto service | 100000 2,3,4 111/tcp rpcbind | 100000 2,3,4 111/udp rpcbind | 395183 1 63846/tcp |_ 395184 1 59049/tcp 111/udp open rpcbind 2-4 (RPC #100000) | rpcinfo: | program version port/proto service | 100000 2,3,4 111/tcp rpcbind | 100000 2,3,4 111/udp rpcbind | 395183 1 63846/tcp |_ 395184 1 59049/tcp 4000/tcp open remoteanything? 5900/tcp open vnc VNC (protocol 3.8) | vnc-info: | Protocol version: 3.8 | Security types: | None (1) |_ WARNING: Server does not require authentication 59049/tcp open unknown 1 (RPC #395184) 63846/tcp open unknown 1 (RPC #395183)
Mounting Network Shares
While the lack of a web interface was a bit of a downside, there was an unexpected find. The 2-series is capable of mounting network shares for storage of data (e.g. screenshots, settings and waveforms). This is a big convenience as it reduces the need to use physical USB storage media, although though the speed and reliability will depend on the network and the server at the other end.
It can be accessed through the “File Utilities” menu through the “Mount” button. Assuming you enter the details correctly, it will be mapped to a drive letter which is then usable throughout the oscilloscope’s UI. The mount details are remembered through reboot cycles.
I had no problems mounting a Samba share from a server running on Ubuntu Linux. Both storage and retrieval operations were reliable and seamless, allowing me to store screenshots directly into my “work-in-progress” folders.
SCPI Benchmark
I tested the SCPI command speed of the MSO24 using my own scpibenchv1 (which is, admittedly, more targeted at PSU, SMU, DMM, etc), but modified as the MSO24 doesn’t support the SYST:ERR? command, instead replacing it with *ESR?.
Testing based on USB, Ethernet (VXI-11 and SOCKET) resulted in speeds as above. The results suggest the MSO24 is not quite a champion at speed – the best devices easily manage 1ms for simple queries such as *IDN?. However, clocking in at 2ms does put it in the fast category. A somewhat more complicated query of *STB? required about 7ms, which is a bit on the slower side as most instruments manage a response in ~4ms. As expected, speeds on USB were slightly faster than speeds recorded over Ethernet.
Conclusion
The Tektronix 2-series MSO offers USB-host, USB-device and Gigabit Ethernet connectivity options. The USB-host feature allows for connection of USB mass storage devices for file operations and the use of USB human interface devices such as keyboards and mice to control the user interface. Testing showed the MSO was able to mount FAT, FAT32, NTFS and exFAT formatted drives, but only appears to mount the first partition.
The USB-device port provides a USB-TMC class interface for accessing the programmatic interface through the use of SCPI commands. Where an appropriate VISA layer is installed, the universal IVI driver is installed, allowing the device to be used.
The Ethernet interface provides the ability to access the programmatic interface through the socket server by VXI-11 or by raw socket connection. Unfortunately, it seems the MSO24 doesn’t use mDNS and thus auto-detection of instruments on the network does not occur and it must be manually added to the VISA layer. The MSO24 also doesn’t have a web interface such as e*Scope found on the higher-end (3-series MDO and above) models. Remote control access to the screen is also available via VNC, which supports setting a password. Unfortunately, this does not include access to the front-panel buttons and knobs, which makes some operations quite difficult to achieve solely through VNC. It does, however, have the very useful ability to mount network shares as if they were local drives and use them to store and retrieve data.
Benchmarking of the performance of the remote interfaces showed that the MSO24 has relatively middling performance compared to other test equipment. The interfaces did perform reliably based on tests which were conducted in a later chapter.
Unfortunately, Wi-Fi is not one of the interface options, which would be handy for using network and internet-connected features while in-the-field and where Ethernet is not readily available. I did try an assortment of USB-Wi-Fi adapters in my possession, however, none elicited any change from the UI.
Provided documentation includes a programmer's manual which is comprehensive and clear. The command-set, however, seems to favour fewer functions which return large "blobs" of text for status information that requires more parsing than I am ordinarily used to. There is also a GitHub account with examples for oscilloscopes, although none are specific for the 2-series MSO at this time. Finally, an TekSeriesScope IVI-COM driver is also provided.
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This blog is a part of the Tektronix 2-series MSO RoadTest Review.