Yes, interested in updates. I'd considered a similar project but actually very rarely need a signature analyser - which makes paying inflated prices even less attractive, and making use of someone else's design more attractive.
You might consider running it on the RP2040 processor. It's cheaper than AVR and has loads of ram. I don't know if it's fast enough to do the capture in software-? it probably still needs the external CRC calculation. What's the maximum clock speed of a signature analyser ?
I also wonder if the Logic Dart could be revisited with modern components. Enthusiasm for the device is variable but some find it useful.
