Saleae Logic Analyzer

[bigmessowires]

Saleae just sent me a Logic Pro 8 logic analyzer. I guess they're trying to raise awareness in the hobbyist/hacker community by sending free hardware to bloggers they like, buying themselves some publicity with a review. Sweet!

Anybody ever use one of Saleae's units before? This new one looks pretty nice. It's actually a combination of an 8-channel digital logic analyzer, and 8-channel analog recording tool (what do you call this, an analog analyzer??) It'll do 500 digital megasamples/sec, or 50 analog megasamples/sec. I can't wait to try it out, but I already wish it had more channels. 8 channels will be enough for Floppy Emu debugging, or working on other serial-oriented systems. But for CPU projects or other systems with wide parallel busses, 8 channels just won't cut it. I have an ancient HP 1631D that's a clunky boat anchor, but it's got 43 channels! 

For some reason Saleae has has decided to discontinue their old 16 channel, digital-only analyzer. Their only 16-channel offering now is the top of the line Logic Pro 16, which has other bells and whistles that not everyone needs. If they had a 100 MHz digital only model with 16 channels, I think it would be popular. Not everyone needs 16 channels *and* 500 MHz sampling *and* analog recording for $499. To be honest, I'm not sure how useful the analog capabilities will even be, since most people using this hardware will already have a regular oscilloscope. Maybe it's good for catching glitches or out-of-spec voltages? I guess I'll found out… this is going to be fun!

 

[Gorgonops]

I have one of the original 8-bit binary-only Logic's rattling around in the garage and I wish I had more time/skill/ideas with which to play with it. The last time I used it was when I was in the process of repairing an old Commodore PET and it was absolutely awesome for checking out the hunches I came up with while staring at the schematics. (My old oscilloscope doesn't have any memory features and has only two channels so it's less than great for checking out "When this line *and* that line are high then this line should be low" situations. I'm sure any old logic analyzer would do, but the Saleae was slick, easy to set up, and of course far cheaper than a new "real" logic analyzer.)

Really the only thing I could complain about is, yeah, even *one* more channel would have been nice. There were a couple situations where it would have been really handy to be able to watch, say, all 8 data lines on the 6502 and have one more signal to connect to a chip enable/rw signal.

 

[olePigeon]

I still don't even know what they're used for.

 

[bigmessowires]

They help you capture the values on a bunch of different wires over a short period of time, maybe up to 1 second in duration depending on the memory capacity and sample rate. Then you can review what happened during that interval, and look for stuff that isn't what it's supposed to be. Super helpful for debugging problems with digital systems. 

You get a result that looks something like this: 

 

[olePigeon]

Hmm.  Don't suppose I could lend you my SE with Funky Video and you might be able to see what the pins do on the video card?

 

[Gorgonops]

An oscilloscope would probably be more useful for that. Mine only samples up to 15Mhz, which I'm pretty sure is too slow, otherwise I'd say I'd be willing to slap the thing on my workbench and poke it. (... to see if my idea with using a few resistors to interface it to VGA holds water.)

 

[bigmessowires]

Yeah ole Pigeon, I could probably take a look at it some time. What is it exactly?

I got a follow-up email from Saleae sales today, they want to schedule a call for me with their CEO to discuss my experience with the LA unit. Should be interesting, but do they really care about my opinion enough to spend the CEO's time on it? Now I feel more pressure to give the thing a thorough testing...

 

[olePigeon]

It's a Mac SE with a custom Lapis video card.  I got a signal out of it the other day, but it's kinda scrambled.  It's almost VGA, but not quite.

 

[bigmessowires]

In that case, I agree with Gorgonops, you need an oscilloscope. I assume you've already tried it with one of those dial-a-mode Mac-to-VGA adapters, and none of the available modes worked?

 

[olePigeon]

Yeah, but it's a different kind of interference.

 

[trag]

Take a look at Intronix's Logicport, LA1034.   It's a 34 channel 500 MHz logic analyzer for $389.   We use them at work.

I'm trying to figure out if the software will support two units simultaneously though.    On some of these old Macs, it would be nice to have about 70 channels.   32 for data.  32 for addresses.   And a handful of others for the control/arbitration signals.

For vintage work, if they would make an 80 channel (nice multiple of 16) 200 MHz or even 100 MHz analyzer, that would be perfect.    In fact 100 MHz would be fine for vintage work, or maybe 133 MHz, just to catch those late model G4s and similar.    Or a 40 channel 100 or 200MHz unit, but write the software, so that if you plug two units into the same computer you can double the channels.   I'm not sure if the computer bandwidth will support that, but it would be cool if it would.  I guess you'd have to hook both units up to the same Clock pin or something, so you'd loose at least one channel to duplication.

 

[bigmessowires]

Wow, 34 channels @ 500 MHz for $389 is great! Is the software decent? That seems like a better deal than the Saleae units.

I suspect it won't actually sample all 34 channels at 500 MHz though. Usually there's some multiplexing going on with these things, so you only get the maximum sampling rate when you're using 1 or 2 channels. Saleae's top of the line Logic Pro 16 will do 4 channels at 500 MHz, but with 16 channels you only get 100 MHz sampling. And depending on what you're doing, you might need 2x oversampling, so 100 MHz sampling might only be good for a 50 MHz system under test.

You could always connect two units to two different PCs if you need 68 channels.

 

[bigmessowires]

I finally had a chance to try out the Saleae unit today, and I have to say I didn't love it. Maybe it's a case of wrong expectations rather than anything fundamentally wrong with it, but I'd say this almost isn't a logic analyzer at all. It's more like an 8-channel, 1-bit oscilloscope. The software has no state analysis features at all, and only the most rudimentary support for parallel busses. Given that, I guess I understand why the hardware doesn't have more channels, because the software just isn't designed for working with that kind of system. If you want to do something like trigger when the value on the address bus is between 0x400000 and 0x410000, or when signal state ABC is followed by DEF, or just look at the state of the system from one clock cycle to the next in a list view, you can't.

You also can't connect an external clock source to determine when samples are captured. That means you have to run the Saleae's internal sampling clock at a few times faster than the clock on the system under test, oversampling the signals. Then you have to deal with the fact that there's an unknown phase relationship between the internal and external clocks, and the Saleae's 10 MHz clock probably isn't precisely the same speed as the system's 10 MHz clock. All of this may cause occasional weird or wrong-looking samples, if the Saleae takes a sample in the middle of your system's clock cycle, when a signal value is right in the middle of a transition.

Maybe I'm being too hard on this thing, or my harping about state analysis and external clocks reflects a "legacy mindset" that's only relevant for bus-based systems. If you were using the Saleae unit solely to troubleshoot an SPI, I2C, or other serial connection, it would probably be fine, though even there some basic features seem to be missing. For example, you can't trigger on a particular SPI value, and the options for searching for particular values or states in the captured data are fairly weak.

I'm not really sure what kind of audience Saleae is aiming for. It seems like it may be the casual hobbyist or Arduino user, but $400 - $500 for a tool in that marketplace is pretty expensive. I don't necessarily expect Saleae's hardware to have the same features as professional equipment from Agilent that costs thousands of dollars… except that most of what's missing seems like it would only require a software change, not anything on the hardware end. The Logicport LA1034 that trag mentioned is in the same price range, and from what I can tell it has most of the features the Saleae is missing. Even the open source hardware "Open Workbench Logic Sniffer" has many of those features, and it also has 32 channels and only costs $50.

 

[Gorgonops]

I'll totally admit that my expectations for it were really low, which was probably why I liked it. For the majority of the instances I used it I was pretty much looking to see if signal "X" was ever high during some period in which signals Y and Z were doing something, and if so, for how long. (A job my ancient oscilloscope wasn't great at, lacking no memory/"freeze frame" functions.) Pretty much anything remotely like a logic analyzer would do the job.

I'm surprised Saleae charges as much as they do now. When the original "Logic" came out it was priced quite reasonably. (The intro price was something like $79? Maybe $99?) The $200-$500 they're charging now seem much less compelling, especially considering the improved competition.

 

[Bunsen]

Saleae / the top of the line Logic Pro 16 / 16 channels *and* 500 MHz sampling *and* analog recording for $499.

That sounds like pretty remarkable value to me.  And I'm in the market.

... but having read your review, I guess I'll be looking at other units still.

Have you tried it with any other software?

 

[bigmessowires]

I don't think there's any other software that supports the Saleae hardware. Their software is very nice at what it does, it's just missing a lot of stuff. Maybe because the hardware can't do it. 

I recently finished up a lengthy review of the new Saleae logic analyzer (10 pages), but it won't be posted until early January, after I have a chance to talk Saleae directly. I specifically tested the Logic Pro 8, but the other models only differ by number of channels, sample rate, and price. Briefly, it's great for basic stuff, and the software is very well polished. But it's missing some important features for more complex work, like an external clock input, state mode, and any kind of meaningful triggering or searching capability. The analog inputs have such low bandwidth as to be of questionable value. The advertised 500 MHz sampling is only for three channels - if you use all 8 channels it's 100 MHz. Then you need to do 4x oversampling, so you can only work with systems running at speeds up to 25 MHz. Most hobbyists probably would have been just as happy with the (discontinued) original Logic at $149, as with this thing at $399. If you need more than the basics, the LA1034 LogicPort that trag mentioned looks very appealing at $389, true 500 MHz sampling with all 34 channels in use. The software isn't as pretty as Saleae's, but from what I can see it's very capable.

 

[bigmessowires]

I posted the full review of the Saleae logic analyzer today: http://www.bigmessowires.com/2015/01/07/saleae-pro-8-logic-analyzer-review/

Saleae scheduled a phone conference for me yesterday with the CEO and another guy, but when the time came they were no-shows. When I followed up by email to ask what happened, they never replied. Grrr….

 

[Paralel]

Screw'em if they can't be decent and keep to their scheduled time nor reply to a follow-up e-mail.

 

[Trash80toHP_Mini]

. . . I have to say I didn't love it. Maybe it's a case of wrong expectations rather than anything fundamentally wrong with it:

I'd say this almost isn't a logic analyzer at all. It's more like an 8-channel, 1-bit oscilloscope. The software has no state analysis features at all, and only the most rudimentary support for parallel busses. Given that, I guess I understand why the hardware doesn't have more channels, because the software just isn't designed for working with that kind of system.

< snip >

You also can't connect an external clock source to determine when samples are captured. That means you have to run the Saleae's internal sampling clock at a few times faster than the clock on the system under test, oversampling the signals.

< snip >

Maybe I'm being too hard on this thing, or my harping about state analysis and external clocks reflects a "legacy mindset" that's only relevant for bus-based systems. If you were using the Saleae unit solely to troubleshoot an SPI, I2C, or other serial connection, it would probably be fine, though even there some basic features seem to be missing.

< snip >

I'm not really sure what kind of audience Saleae is aiming for. It seems like it may be the casual hobbyist or Arduino user, but $400 - $500 for a tool in that marketplace is pretty expensive.

< snip >

The Logicport LA1034 that trag mentioned is in the same price range, and from what I can tell it has most of the features the Saleae is missing. Even the open source hardware "Open Workbench Logic Sniffer" has many of those features, and it also has 32 channels and only costs $50.

Do you have any idea about the value of those comments from a marketing/development standpoint? They really ought to send you their high end system as a thank you (and to entice even more such feedback!) for the value they got in exchange for their costs on that $499 MSRP Analyzer.

A 24 hour turnaround on an email from a small(?) company added to a lapse in communications and attention doesn't add up to a mortal sin. They're probably still trying to get together on what the heck to ask you!

I used to beta test CAD/CAM equipment and software for vinyl/film cutting equipment in the sign business back around the beginning of the early Nineties. I was the "CEO" of a "two guys in a garage" level ROM/Font Emulation startup for same. I got lots of toys from both endeavors and the satisfaction/frustration of seeing an offhand comment I let slip about something I had in mind turn into a shipping product from another such company. They got that one for the price of a dinner their "CEO and CTO" bought me at a Sign Industry convention!

They'll likely get back to you. [ ]

*** edited two letters for language content in order to preserve G Rating of post.

edit: LOL! Just realized that that two letter edit can be construed as having been applied from either direction, both inappropriate, but totally applicable! [] ]'>