Logic Analyzer Buying Advice

John Board

G'day,

I've been looking at getting a (USB) Logic Analyzer over the last few days. The biggest one I've seen around is the Saleae range of products. They look nice but several reviews have revealed that they may be overpriced and their triggering functionality may not be quite up to scratch. I have seen others, but not as prominently.

My question is, what USB Logic Analyzers do you guys use, and/or which ones would you recommend? I'm not closed to getting the Saleae ones, but I want to look through my options first.

My minimum required specifications are very similar to the Logic Pro 8:
- 8 Digital Inputs (Analog as well would be nice, but not a requirement)
- +100MS/s
- Good software, with reasonable triggering and decoding capabilities. (Scripting would be nice)
- Streaming to computer (and hence, storing captured information in RAM allowing for long captures), or reasonable memory depth.

I have found some around which fits those specs, but I trust recommendation over advertisement.

Thanks for your help!

-John

jmg

Software matters of course, but at the HW level the design approach I favour for Logic capture is time-stamped edges,
That gives a natural compression and very wide dynamic range and you do not need to decide a capture rate compromise, or risk miss of glitches at low capture rates.

evanh

Well, analogue input is an oscilloscope rather than a logic analyser but that's what I've always used. A four channel DSO with megabytes of capture RAM is pretty damn flexible. The deep memory totally deals to aliasing and serial data searches and can be used to follow sequencing with large time scaling no problem. Newest ones have a gigabyte or more.

Of course the bigger logic analysers have a ton of inputs that a scope will never compete with but to be honest I'm not sure if anyone much tries to read 64 bit data and address lines these days.

The big bonus with scopes is you get to see the real shape of the signal; which can immediately alert you to a problem you weren't thinking about.

prof_braino

For logic level changes connected to the prop, we use the propforth logic analyzer. It runs on 1 to 4 cogs, and has three mode. Price: free! If you already has a prop board.
Mode 1 - runs on 1 cog and logs to unused cog ram. Fast, but small sample size.
Mode 2 - runs on 1 cog and logs to unused hub memory. slower, but very large sample size
Mode 3 - runs on 4 cogs and logs to hub ram. Fast, and large sample size, but uses half the cogs.

The fast logging can capture each transition of the prop clock.

The samples are displayed on your terminal program screen on your PC. Needs no additional wires or probes for items already connected to the prop, display 0 to 32 pins of interest.

Of course, its in forth, so some effort may be required to modify the code.

Code is included in the extensions directory in the propforth.zip downloadable from google code.

CRST1

Just a caution on speed. We use a number of data recorders at work. Most recorders (not all) will give you a speed, say 100Ms/s or maybe 200 khz, but the more channels you use divides the speed by two for each additional channel. A lot don't tell you that when they quote speed. We have been thruogh a lot of recorders thru the years and have only found a couple that don't slow down with channels used. Digital doesn't make as much change due to it is only looking at edges. If you want analog that makes a difference. We have gone thru ones hooked to computer, standalone with memory cards that you load into computer after capture and now the only one we use is the AstroMed brand with built in drives and large graphic screen, but we are talking big dollars like starting at $15k for 8 channels.

Just be carefull when they quote the speed of recorders. Do the work of checking very closely before buying.

davejames

John Board wrote: »

My question is, what USB Logic Analyzers do you guys use...

USBee offers a number of products, of which I personally use the USBee SX:

http://www.usbee.com/sx.html

It probably doesn't meet your list of requirements, but check out their other offerings.

Peter Jakacki

John Board wrote: »

G'day,

I've been looking at getting a (USB) Logic Analyzer over the last few days. The biggest one I've seen around is the Saleae range of products. They look nice but several reviews have revealed that they may be overpriced and their triggering functionality may not be quite up to scratch. I have seen others, but not as prominently.

My question is, what USB Logic Analyzers do you guys use, and/or which ones would you recommend? I'm not closed to getting the Saleae ones, but I want to look through my options first.

My minimum required specifications are very similar to the Logic Pro 8:
- 8 Digital Inputs (Analog as well would be nice, but not a requirement)
- +100MS/s
- Good software, with reasonable triggering and decoding capabilities. (Scripting would be nice)
- Streaming to computer (and hence, storing captured information in RAM allowing for long captures), or reasonable memory depth.

I have found some around which fits those specs, but I trust recommendation over advertisement.

Thanks for your help!

-John

I use the Digiview DV3100 and I'm pretty happy with it. It can also decode various protocols such as I2C, SPI, ASYNCH, etc.

Publison

evanh wrote: »

Well, analogue input is an oscilloscope rather than a logic analyser but that's what I've always used.

Just so you know, the new saleae LA can do both Analog and Digital inputs.

https://www.saleae.com/

Tracy Allen

I have one of the earlier Saleae 8-channel devices and turn to it quite often for protocol decoding of i2c, spi, rs232. I'm very happy with it for that purpose. The interface is uncluttered and intuitive for a quick learning curve. My DSO does not do protocol decoding, but it is there to look for analog anomalies. The Saleae does not have a trigger output for the 'scope though, so there is no possibility for triggering there except by strategically locating trigger events in your own code.

Another possibility is the Analog Discovery from Digilent. Not just analog, it includes a 16 channel logic analyzer with multiple i/o capabilities. It's technical document is very thorough. The interface and learning curve is steeper simply because of the host of features.

localroger

Adding another vote for the Saleae. It's a solid product, well made with easy to use and reliable support software.

Don M

+1 for Saleae. I've had their device since inception. Good support. Simple and easy to use.

David Betz

Don M wrote: »

+1 for Saleae. I've had their device since inception. Good support. Simple and easy to use.

Agreed. Another advantage, for me anyway, is that there is software available for the Mac.

tomcrawford

+1 Saleae. Had one of the old ones and now have one of the new ones. Saved a project more than once.

David Betz

tomcrawford wrote: »

+1 Saleae. Had one of the old ones and now have one of the new ones. Saved a project more than once.

Do you find the new ones superior to the old ones? In what ways? I guess a big advantage of the ones is that they can support analog inputs. Is that the main reason for upgrading or are there other improvements?

tomcrawford

David Betz wrote: »

Do you find the new ones superior to the old ones? In what ways? I guess a big advantage of the ones is that they can support analog inputs. Is that the main reason for upgrading or are there other improvements?

I got the new one purely for analog input. I have to admit to being a little disappointed in finding you have to have USB 3.0 to get the full sampling rate in analog.