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  • EEVblog #44 – Part 2 – Logic Analyzer Tutorial

    Posted on November 16th, 2009 EEVblog 15 comments

    Part two of Dave’s Logic Analyzer tutorial / monologue

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    • TrentO

      Very informative! Thanks Dave.

      -Trent

      P.S.: Do you have crickets that actually live IN your garage?

      • http://www.eevblog.com EEVblog

        Not IN the garage, they are just damn LOUD!

    • http://kaqelec.dyndns.org Kathy Quinlan

      http://www.pctestinstruments.com/

      That is the LA I use, it is good for debugging code ;) I actually found a bug in some code I bought (they were initialising the LCD in the wrong order ) I also use it to debug serial streams between devices :)

      It takes up very little bench space and I run it on both my desktop and laptop (good for in the field ;)

      Regards,

      Kat.

      • Scott Burris

        Kat,

        Have you used your LA on high speed circuits, say SDRAM memory with success? I’ve got a Tektronix 1240 LA, but it’s too slow (100Mhz) for such things.

        I’m interested in higher speed USB LAs, but I’m concerned that the leads may load down high speed buses too much.

        Scott

        • http://kaqelec.dyndns.org Kathy Quinlan

          Hi Scott,

          I have not used my LA on high speed circuits yet, I only use it to debug AVR’s.

          Luckily I am not needing the power of the new ram chips with the uber tight timing, I cn still get away with ancient slow ram ;)

          Regards,

          Kat.

    • Brian Hoskins

      I found it hard to believe that they could be actual crickets, especially as they periodically seemed to shut up, so I started wondering if perhaps the capstan motor was in trouble!
      But I’m guessing your new camera uses solid state storage anyway, so I’m probably wrong there. Damn loud those crickets!!!

      It’s funny you should do a blog on Logic Analysers because just yesterday I was shopping around for one on the internet. I have quite a nice storage scope for most of my needs but it’s quite useful to have a logic analyser kicking around every now and then. Especially if you’re experimenting with a project that’s taking you into new territory with regard to your experience or knowledge. I’ve suffered that recently whilst writing code for a PIC to control a serial GLCD (hacked from a Nokia phone) and could have done with such a device.

      Great blog, well done.

      Brian

    • bmwm3edward

      Great blog, Dave. I learned more in the 20 minutes about these than I would in many hours of my own research, not to mention averting a misinformed buying decision.

    • Gerhard Hoessle

      Scott,

      I also have the Intronix Logicport. I’ve been using to analyze DDR and SDR SDRAM interfaces running at 100MHz+, along with other FPGA development projects. I’ve found it to work very well, especially its trigger capabilities.

      As far as “leads loading the circuit”, any analyzer (even the most expensive Agilent unit) will effect your circuit because all of them have finite input impedance. So the question becomes how much of an effect, and can your circuit tolerate it. I chose the Logicport partly because it has the lowest input capacitance of any PC-based analyzer I’ve found in its speed/price range. That’s a critical spec for high-speed work. As Dave’s tutorial pointed out, its adjustable input threshold and relatively short leads are also helpful when sampling high-speed signals.

      Gerhard

      • Scott Burris

        Looks like I’m going to make another purchase then — darn you EEVBLOG, I keep finding ways to spend money!

        I picked up the Rigol DS1502E from Hong Kong for $400US since Dave seemed to like his so much, and I’ve been quite happy with it.

        Maybe Santa will bring me the Intronix Logicport for Christmas. I should go look at the unit Dave is waving about in his blog and compare specs.

        Scott

    • Fernando Casar

      If you are debugging low speed circuits, you could make a parallel port logic analyzer.
      Once I needed to “sniff” an i2c communication on a project and I was in a hurry, so I couldn’t get a real analyzer. I googled around and found this:
      http://www.xs4all.nl/~jwasys/old/diy2.html
      it worked for my purpose, I know it’s not near to a real professional analyzer, but in certain circumstances can still be useful.

      pd: By the way I was supposed to use an HP1651B at work in that time, but nobody had used it in a lot of time and they had lost the system diskette.
      I was forced to find a quick and cheap solution.

    • BoBoo

      well , your getting there, but not much of a tutorial, just a slurp from the tea cup, but better than the co co pop caps one

    • Mario

      Dave,

      You neglected to mention two of the most important points about LA’s:

      1/. Flexible trigger options and programming thereof.

      2/. The software used to analyze the resulting data.

      I think, after years of working with LA’s and relying upon them, these two issues are forgotten about, but are probably the most important – especially when using the things!

      Love the vlog!

      Mario.

    • http://www.andrewcraigmackenzie.com Macka

      Is this the sort of thing you would use to debug/reverse engineer a CPU?

      I know a team of people reverse engineered the Nintendo Wii CPU’s with FPGA’s.

      As far as I understand an FPGA is much faster then most logic analysers, so which is better [for logic analysis]?

      • Jim

        Macka,

        I’ve also heard that stainless steel is much stronger than most bananas, so which is better [to eat]?

    • http://nvistech.com Microwave Technology

      What a great blog and thanks very much for the heads up.