Building a Swiss Army Lab With Software Defined Instrumentation

Source: Hack a Day

Article note: Is this a sponsored ad? These things looks like they compare poorly even to the established direct competitors. At the high end, their Lab and Pro models are in competition with the big-name modular instrument things (NI VirtualBench, Keysight's lower-end Modular lines like the Streamline stuff), and priced like it, and I'm not sure they're credible enough to play in that (conservative and expensive) market. In the mid-range, there are a number of established relatively inexpensive USB-attached electronic multi-tools, like the Analog Devices ADALM2000 https://www.analog.com/en/design-center/evaluation-hardware-and-software/evaluation-boards-kits/adalm2000.html ($175; 2x 100MSPS oscilloscope channels, 2x AFG, 0 to +5V and 0 to -5V programmable PSU, 16x DIO, choice of Scopy software that runs on Windows, OSX, Linux, or Android) and Digilent AD2 https://digilent.com/shop/analog-discovery-2-100ms-s-usb-oscilloscope-logic-analyzer-and-variable-power-supply/ (price has recently spiked to $399; 2x 100MSPS oscilloscope channels, 2x AWG, 0 to +5V and 0 to -5V programmable PSU, 16x DIO, Waveforms software that runs on Windows, Mac OS X, and Linux). The bottom-of-the-line Moku:Go M0 is $599 and missing the power supplies, the M1 is $700 and the only feature I see differentiating it from the USB-multitool competition is a PSU channel that can get up to +16V. Also, the mid-range USB-attached-instrument-pod market is getting squeezed from above, since you can get into a mid range oscilloscope with built-in passable AWG for like $1k (Think Rigol MSO5000 or Siglent SDS2000X Plus). Admittedly they don't have the nice programmable digital IOs even if you add the 16CH logic pods for another $500ish, and also lack the (feeble) built-in PSUs, but they are a _lot_ more instrument. And that market is being squeezed and from below, by the various little USB scope and IO boxes (Look at Sigrok (https://sigrok.org/) to avoid their usually-awful vendor software, think Hantek shitboxes and FX2 based gadgets) in the $25-100 range, or even things like the buck50 stm32 firmware ( https://github.com/thanks4opensource/buck50 ) that gets you a rough low-end instrument pod on a $2 dev board. I've been teaching a class largely using AD2s (and/or the larger ElectronicsExplorer that is on the same platform) for years, and the department I work in has a cohort trying out the ADALM2000 this year because the AD2 prices and availability were getting unreasonable and it looked like the next thing to try when we surveyed the market. They make great basic I/O and _very_ limited PSUs (almost of a feature, they cut off automatically on current spikes which helps avoid dead chips), but their scopes are both mediocre enough that I'll reach for a bench scope when it's available even if I already have the pod hooked to my circuit for other functions.

It’s a fair bet that anyone regularly reading Hackaday has a voltmeter within arm’s reach, and there’s a good chance an oscilloscope isn’t far behind. But beyond that, things get a little murky. We’re sure some of you have access to a proper lab full of high-end test gear, even if only during business hours, but most of us have to make do with the essentials due to cost and space constraints.

The ideal solution is a magical little box that could be whatever piece of instrumentation you needed at the time: some days it’s an oscilloscope, while others it’s a spectrum analyzer, or perhaps even a generic data logger. To simplify things the device wouldn’t have a physical display or controls of its own, instead, you could plug it into your computer and control it through software. This would not only make the unit smaller and cheaper, but allow for custom user interfaces to be created that precisely match what the user is trying to accomplish.

Wishful thinking? Not quite. As guest host Ben Nizette explained during the Software Defined Instrumentation Hack Chat, the dream of replacing a rack of test equipment with a cheap pocket-sized unit is much closer to reality than you may realize. While software defined instruments might not be suitable for all applications, the argument could be made that any capability the average student or hobbyist is likely to need or desire could be met by hardware that’s already on the market.

Ben is the Product Manager at Liquid Instruments, the company that produces the Moku line of multi-instruments. Specifically, he’s responsible for the Moku:Go, an entry-level device that’s specifically geared for the education and maker markets. The slim device doesn’t cost much more than a basic digital oscilloscope, but thanks to the magic of software defined instrumentation (SDi), it can stand in for eleven instruments — all more than performant enough for their target users.

So what’s the catch? As you might expect, that’s the first thing folks in the Chat wanted to know. According to Ben, the biggest drawback is that all of your instrumentation has to share the same analog front-end. To remain affordable, that means everything the unit can do is bound by the same fundamental “Speed Limit” — which on the Moku:Go is 30 MHz. Even on the company’s higher-end professional models, the maximum bandwidth is measured in hundreds of megahertz.

Additionally, SDI has traditionally been limited to the speed of the computer it was attached to. But the Moku hardware manages to sidestep this particular gotcha by running the software side of things on an internal FPGA. The downside is that some of the device’s functions, such as the data logger, can’t actually live stream the data to the connected computer. Users will have to wait until the measurements are complete before they  pull the results off, though Ben says there’s enough internal memory to store months worth of high-resolution data.

Of course, as soon as this community hears there’s an FPGA on board, they want to know if they can get their hands on it. To that end, Ben says the Moku:Go will be supported by their “Cloud Compile” service in June. Already available for the Moku:Pro, the browser-based application allows you to upload your HDL to the Liquid Instruments servers so it can be built and optimized. This gives power users complete access to the Moku hardware so they can build and deploy their own custom features and tools that precisely match their needs without a separate development kit. Understanding that obsolescence is always a problem with a cloud solution, Ben says they’re also working with Xilinx to allow users to do builds on their own computers while still implementing the proprietary “secret sauce” that makes it a Moku.

It’s hard not to get excited about the promise of software defined instrumentation, especially with companies like Liquid Instruments and Red Pitaya bringing the cost of the hardware down to the point where students and hackers can afford it. We’d like to thank Ben Nizette for taking the time to talk with the community about what he’s been working on, especially given the considerable time difference between the Hackaday Command Center and Liquid’s Australian headquarters. Anyone who’s willing to jump online and chat about FPGAs and phasemeters before the sun comes up is AOK in our book.


The Hack Chat is a weekly online chat session hosted by leading experts from all corners of the hardware hacking universe. It’s a great way for hackers connect in a fun and informal way, but if you can’t make it live, these overview posts as well as the transcripts posted to Hackaday.io make sure you don’t miss out.

This entry was posted in News. Bookmark the permalink.

Leave a Reply

Your email address will not be published.