3 ms·

Never did electronics, so when I've read of logic analyzers in a book, it sounded like something between an oscilloscope and a complex gadget out of a story fro

Never did electronics, so when I've read of logic analyzers in a book, it sounded like something between an oscilloscope and a complex gadget out of a story from Isaac Asimov. It's surprising they're so simple, cheap and effective.

kevin_thibedeau 5y ago
Benchtop logic analyzers used to be more complicated. They are still technically superior with better probe termination, higher sample rates, and sophisticated hardware triggering.
- danhor 5y ago
  The big down side is of course the limited sample memory. Many (especially the very popular, because cheap, fx2la) pc-based ones simply stream the data, which enables the use of all PC RAM and essentially infinite capture times.
  - MayeulC 5y ago
    Last time I tried a cheap ($8) saleae fx2la clone using pulseview/sigrok (open source combo for visualization, with open source fx2lafw), I didn't find a continuous option, but that might have been a GUI issue, thanks for the tip!
    - danhor 5y ago
      You can just set the sample count really high (up to 1 trillion). The samples are not compressed in RAM, so the maximal capture time is determined by the size. For 8 GiG and 24 MHz this means you can capture for ~6 minutes. I tend to simply set the sample count higher than needed and stop the capture prematurely.
  - buescher 5y ago
    If you have a decent oscilloscope with logic/protocol analyzer features, you can trigger the analog scope side of the tool on data. This is a very powerful debugging tool for finding the physical cause of odd data. Yes, with a pc-based tool you can capture everything to disk and go back and search, but that usually works out to be kind of clumsy.
    - kevin_thibedeau 5y ago
      Tektronix introduced some nice LA units 20+ years ago that could be configured with analog mux outputs to pass probe channels over to a scope. The instruments could be cross triggered if you wanted to but it was fun to cycle through a whole address and data bus in real time and look for SI problems.
pkaye 5y ago
A while back Cypress made a programmable chip that had USB capability, programmable general purpose IO and DMA for efficient data transfer. This turned out to be just what as needed to make cheap logic analyzers for hobbyists. https://www.eevblog.com/forum/testgear/logic-analyzer-that-is-using-the-cypress-ez-usb-fx3-chip/ https://www.eevblog.com/forum/testgear/logic-analyzer-that-i...
- duskwuff 5y ago
  > A while back Still in production, still incredibly useful.

kevin_thibedeau 5y ago

Benchtop logic analyzers used to be more complicated. They are still technically superior with better probe termination, higher sample rates, and sophisticated hardware triggering.

danhor 5y ago
The big down side is of course the limited sample memory. Many (especially the very popular, because cheap, fx2la) pc-based ones simply stream the data, which enables the use of all PC RAM and essentially infinite capture times.
- MayeulC 5y ago
  Last time I tried a cheap ($8) saleae fx2la clone using pulseview/sigrok (open source combo for visualization, with open source fx2lafw), I didn't find a continuous option, but that might have been a GUI issue, thanks for the tip!
  - danhor 5y ago
    You can just set the sample count really high (up to 1 trillion). The samples are not compressed in RAM, so the maximal capture time is determined by the size. For 8 GiG and 24 MHz this means you can capture for ~6 minutes. I tend to simply set the sample count higher than needed and stop the capture prematurely.
- buescher 5y ago
  If you have a decent oscilloscope with logic/protocol analyzer features, you can trigger the analog scope side of the tool on data. This is a very powerful debugging tool for finding the physical cause of odd data. Yes, with a pc-based tool you can capture everything to disk and go back and search, but that usually works out to be kind of clumsy.
  - kevin_thibedeau 5y ago
    Tektronix introduced some nice LA units 20+ years ago that could be configured with analog mux outputs to pass probe channels over to a scope. The instruments could be cross triggered if you wanted to but it was fun to cycle through a whole address and data bus in real time and look for SI problems.

pkaye 5y ago

A while back Cypress made a programmable chip that had USB capability, programmable general purpose IO and DMA for efficient data transfer. This turned out to be just what as needed to make cheap logic analyzers for hobbyists. https://www.eevblog.com/forum/testgear/logic-analyzer-that-is-using-the-cypress-ez-usb-fx3-chip/ https://www.eevblog.com/forum/testgear/logic-analyzer-that-i...

duskwuff 5y ago
> A while back Still in production, still incredibly useful.