Low-cost logic analyzer's got game - Embedded.com

Low-cost logic analyzer’s got game

Saleae's new Logic 16 is a well-engineered, low-cost logic analyzer.

In the Jurassic period, all oscilloscopes and logic analyzers were big, bulky, bench instruments that were incredibly expensive. But a decade or so ago a variety of low-cost scopes and analyzers appeared. They are not analogous to the little shrew-like mammal that replaced the dinosaurs, since the high-end devices are essential for lots of engineering work and will never disappear. Instead, these USB-connected instruments fill a niche for those with limited budgets who are not working on bleeding-edge projects. Over the years I've reviewed a number of these.

Saleae's new Logic 16 is a sixteen channel USB-based logic analyzer (LA). It's one of the very few cross platform LAs available, with application software that runs under Windows, Linux, and on the Mac.

Its speed is a function of the number of channels being used. With three the unit clocks data in at up to 100 MHz. Nine channels (somewhat puzzling; one would think eight would be more likely) drops it to 32 MHz, and half that speed is attainable when all 16 channels are in use.

With all of the crazy voltage levels now used in digital circuits, it's nice that Logic supports two voltage ranges: 1.8 to 3.6V and 3.6 to 5V.

Capture data is streamed through short on-device buffers to the host computer, which can handle up to 1 TB of data given minimal transitions (the data is compressed). As a practical matter the software suggests that most host computers can handle up to about 1.8 GB. Like with all of these USB devices one must not overrun the USB connection, but I had no problems at all using a four-year old MacBook Pro with a 16 MHz acquisition rate.

A built-in protocol analyzer decodes CAN, DMX-512, I2C, I2S/PCM, Manchester, 1-Wire, async serial, simple clocked parallel, SPI, and UNI/O.

The Logic 16 comes in a stunning metal case with non-slip rubberized bottom. It's spare, like an iPhone. Beautiful. There are no controls, just connectors for the probes and USB, and one LED. It comes with a zip-up carrying case that is so elegant it could be a high-couture fashion accessory. And it will all fit nicely in a purse for those ad hoc debugging sessions that always seem to come up at wedding receptions and cocktail parties.

Unlike some USB LAs, the Logic 16 does come with micro-grabbers for each of the channels and ground.

Installation is straight-forward, but it does seem to want to install its own USB driver (on the PC). I turned to a Mac installation at that point, since my USB ports were busy handling other experiments.

It's easy to connect the probe wires, and it's just as easy to connect them incorrectly. Doesn't the black wire go to ground? Nope. The instructions are very clear about this. The ground wire is carefully labeled. Black is input 0, because, as is common on these small logic analyzers, the wire colors use the resistor color code to denote their bit position.

The unit comes with neither software nor manual. Cookies, though, are included with the suggestion that, after downloading the application from the company's web site, one should snack on them. A 23-page manual is online.

The residents of Ganssleville enjoyed the Chips Ahoy.

The display is very simple, stark almost, with nothing extraneous on the screen. The black background mirrors the inky black of the machined aluminum case. The ease of use is unmatched by any other USB logic analyzer I've tried. Navigation is breathtakingly fast and smooth.

Click on image to enlarge.

Screen shot of the Logic 16's interface.

Some of these small LAs falter when uploading data to the host computer. It took about seven seconds to acquire and upload 100 million samples (of all 16 channels) gathered at a 16 MHz rate… which is exactly the time required to gather the data. The upload is seemingly instantaneous.Trigger modes are limited. Any single channel can start the logic analyzer on an up- or down-going edge, and that can be combined with a logic one, zero, or don't-care on any combination of the other channels. There are no complex triggering modes, and it's not possible to trigger on just a simple binary pattern sans edge. The reasoning is that the Logic 16 can acquire such a vast amount of data that the event of interest will likely be captured. The company tells me they are working on enhancements to the trigger, as well as adding a search feature to the application.

Width, period, duty cycle and frequency measurements are displayed for the data at the mouse position. Two cursors show absolute time from the trigger event, plus the time between cursors. Interestingly, the delta time measurement also shows its accuracy in percent due to quantization from the acquisition rate.

The binary value of the data at the mouse cursor position is displayed; it can also show hex, decimal, etc. equivalents. But those are shown after the binary, and eat up a lot of screen space. I wish these additional radix displays were below the binary rather than adjacent to it.

Saleae has a community site where they make an SDK available. This means you could develop your own protocol analyzer. The source for all of their analyzers is there, providing a framework on which to base a custom version. I looked at the I2 C module and found that there's not a lot of code required. The SDK found me longing for single analog channel as it would be so easy to make this a data logger, and analog is often more interesting to log than digital signals. But that would be a different instrument.You can give the application itself a whirl, as it will go into a simulation mode if a Logic 16 isn't detected.

I generally prefer a dedicated bench instrument rather than a USB device, as the former's knobs are so much easier to manipulate when probing a board. But the Logic 16's UI is so intuitive, and so easy to manipulate, that it outshines the bench analyzers I've used.Like all of these low-cost LAs the Logic 16 is not feature-rich. Its weakest point is the lack of triggering flexibility. But that aside, it does a good job of providing much of what a much more expensive bench analyzer will do. Too my knowledge it's the only such product that supports Windows, Linux and Mac. The price ($299) is right, it'll slip into a shirt pocket, and the engineering is something Steve Jobs would envy.

Jack G. Ganssle is a lecturer and consultant on embedded developmentissues. He conducts seminars on embedded systems and helps companieswith their embedded challenges, and works as an expert witness onembedded issues. Contact him at . His website is.

12 thoughts on “Low-cost logic analyzer’s got game

  1. I have the older 8 channel version. The best $150 I ever spent on embedded development.

    I use mine under both Linux and Windows and it works a dream.

    Sure they can't do everyting, but they do enough that it is an absolute nop-brainer to give every embedd

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  2. I've used the similar Intronix LogicPort for years. With 34 channels, 500 MHz sampling, and more flexible thresholds I think it's worth the extra ninety bucks or so. Now I'm waiting for a USB 3.0 version with significantly more hardware memory — small sam

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  3. The main reason Saleae didn't go with USB 3 was that USB3 did not exist when this product was made. The Logic products have been available for a few years now. Perhaps they will make a USB3 one sometime.

    That LogicPort product looks interesting too. Pity

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  4. Saleae has certainly come up with a winning product. I have used mine extensively. I have written custom a custom plugin to analyze IR signals. It is well built and the included RS232,I2C capabilities make it invaluable in developing serial applications

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  5. LogicPort, like Saleae, uses compression, so the 2K buffer is not as much of a limitation as it might seem. But it definitely is less than ideal — sometimes I have to hide the frequently-changing signals (like clocks) from a view to get longer sampling ti

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  6. I too have using the Logicport for years – we own two models, one with an external trigger input one can hook to a scope or emulator trigger output to frame an incident. As jadwin79 observed, the compression algorithm helps overcome the buffer depth limit

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  7. Completely agree with the positive review. In my estimation this product was a game changer. I lead a team of 8 firmware developers and last year we purchased one for every member of the team. The benefit that it has been during debugging sessions has p

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  8. According to Wikipedia, USB 3 spec only came out in November 2008. The first USB capable PCs have only been around since 2010 or so and only commonly available later. While Linux has supported USB 3 since 2009, MS Windows has only supported USB 3 since Win

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  9. I have several Windows 7 machines with USB 3 ports: an HP laptop with built-in USB3 ports and a desktop with an add-in card. Those drivers are apparently not native to Win 7, but the result is the same (people are running USB3 on Win XP). I develop imaging

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  10. I *love* my Logic. I burned it out the other day and immediately ordered a replacement. The software is impressive and fairly intuitive, only it hasn't been upgraded in a while.
    I have seen less expensive work-alike hardware, not just on Ebay.
    But I have

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