I need someone to explain this to me.

Adding a serial trigger to a logic analyzer

If you’re attempting to debug a serial bus with a bare-bones logic analyzer, you’re going to have a bad time. Most of the inexpensive analyzers¬†available don’t have a serial pattern trigger, or a way to start recording data after a specific pattern of bits comes down the pipe. [Neil] sent in a great little project that adds a serial trigger to these analyzers, we’ve got to hand it to him for designing such a useful board.

[Neil] designed a small board featuring a CLPD that converts serial data to parallel data. By setting the trigger condition of the logic analyzer to any 24-bit pattern he wants, it’s possible for [Neil] to sniff a serial bus exactly when he wants to.

The circuit is quite minimal, basically just a 100-pin CLPD and a bunch of 0.100″ header pins. It’s a useful tool, and although we couldn’t find the board file to make our own, we’re sure [Neil] will be providing that shortly.

Comments

  1. steve says:

    Nice! And the manual setting makes it very hassle-free. Do I understand correctly, that he can trigger H,L,X? Or just H/L?

  2. miragesneil says:
  3. ino says:

    nice, and you can purchase an EPM240 dev board for 12$ on ebay.

  4. I dont find a 100pin CPLD as simple, but thats just my 1.5 cents, However, I do like it, and I think I might try to do it simpler and as a add on to my LA/Scope.

  5. penguin says:

    Doesn’t saleae already support serial triggers?

  6. Destate9 says:

    Lol Southpark

  7. chango says:

    This should be possible with the Logic Sniffer when the 16500 style trigger setup is added to OLS. Those old HP analyzers were amazing.

  8. dvchench says:

    I keep wondering what kind of potential an Altera DE-1/2 board would have as a logic analyzer (granted, you have to do your own interfacing, level conversion, etc. if that’s necessary). Has anyone tried just using a DE1/DE2 devkit with a computer, and maybe some extra parts? I haven’t messed with this, but I’m sure you can use the GPIO pins on a devboard and configure a LogicTap circuit in Quartus (adding your own custom HDL code to process your inputs however you please).

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