Logic analysis on analog waveforms

Logic 2 (Alpha) Software
#1

Hey Saleae! I’ve been ogling at the pro versions of your logic analyzers for a few months now. It’s a great looking platform, and the new Logic 2 Alpha software looks just fantastic with the live view feature and embedded console.

There’s one feature of which I’m wondering whether it would be possible for your team to implement, as I think none of the logic analyzers currently out there have it, your platform is most suitable for it, and I know many fellow engineers that have needed something similar in the past.

I’m currently working on a large scale project (an entire building encapsulated in custom industrial semi-addressable LED strips) that has signal integrity problems. For that I’ve been needing to analyze an extremely loaded down (400mVpp) 1000 kBaud RS485 signal, hovering around 5 volts. None of the logic analyzers I’ve tried caught it, as their tresholds are way lower, but your platform should theoretically allow me to record the analog signal, pick a threshold (or just have it take the center) and analyze the result of that.

The only thing that gets it now is the scope, but your user interface would be só much more pleasant to work with.

I’m looking forward to hearing whether you’d be able to implement this (and will be dying to purchase one of your analyzers if you have this feature).

Kind regards!
David

#2

I previously suggested the exact same thing to them - make a way for an analog signal to be turned into a digital signal with customized thresholds. This would be handy for so many things.

Here is where ideas for future development are proposed and the link to where I suggested what you also want:

So, you can go there and vote for my idea and maybe some day it will happen. It might help if you happen to be related to Vito “The Leg Breaker” LaGucci.

3 Likes
#3

Hi David, thanks for the idea! Yeah, we sorely need this…

This is theoretically a straightforward solution as you mentioned (all thresholds and transformations would be handled via software). I just added a link to your post here in the idea post that @Collin shared so that we can get your use case recorded.

1 Like
#4

Sweet! Thanks a lot for the active engagement.

One last thing I’d like to add; if this feature would be implemented it would be increasingly helpful if there was the option to substract two analog (differential) signals and use the zero-crossing point as the reference for the digital conversion. This way you would be able to analyze the exact signal (and its timing) the logic IC itself would also see.

(I have once encountered a problem where a differential signal was daisy chained through many, mány chips, which all stretched the high pulses slightly, leaving the low ones awkwardly short, leading to all kinds of different problems. With this feature the timing of that could also be analyzed - something even an oscilloscope can’t naturally do.)

#5

As far I know even thresholds for digital signal is not working yet for logic 2
Doesn’t matter if you set 3.6v it will change to logic 1 near 1.1v
They already confirmed that is on queue to be fixed (it works on logic 1)

#6

There is a bug in the Logic 2 software, specifically you cannot change the digital voltage setting for the original Logic16 (discontinued in 2014).
The other 2 products which support adjustable digital voltage settings, Logic Pro 8, and Logic Pro 16, should work properly. If you notice a problem with the voltage threshold on one of those devices, please let us know!

(the problem with the original Logic16 is that changing the digital threshold requires a 5 second hardware reset. We will eventually allow you to change the voltage setting on the original Logic16 in Logic 2, but we will probably put it in the app preferences, and you will need to unplug and re-plug the device. The newer products don’t have this problem, and should take the new voltage setting instantly. The Logic 1.x software does support this with the original Logic16, that’s why when you change its voltage setting, you get a popup that blocks for about 5 seconds)

One last thing I’d like to add; if this feature would be implemented it would be increasingly helpful if there was the option to substract two analog (differential) signals and use the zero-crossing point as the reference for the digital conversion. This way you would be able to analyze the exact signal (and its timing) the logic IC itself would also see.

@inevitableavoidance, we do want to add analog math channels in the future, as well as the ability to convert an analog channel into a digital one using a custom threshold. Ideally, this would be done using extensions, so that users could write custom conversion functions. This would open the door to a lot of other possibilities too! Unfortunately we won’t be able to get back to the extension system soon, we’ve bit off a huge project that’s going to tie us up for a while. Looking forward to getting back to extensions though!

#7

Ok. I will wait for that.
I believe that on application code should be same “commands” to change the threshold.