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.
10 thoughts on “Adding A Serial Trigger To A Logic Analyzer”
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?
You are right, it can trigger H, L and X.
Hi everyone, here is the Gerber file of the PCB:
nice, and you can purchase an EPM240 dev board for 12$ on ebay.
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.
Doesn’t saleae already support serial triggers?
This should be possible with the Logic Sniffer when the 16500 style trigger setup is added to OLS. Those old HP analyzers were amazing.
Actually the standard logic sniffer software already supports serial triggering!
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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