Logic priate, noise bofre trigger

The Logic Pirate is a medium speed, low-cost logic analyzer with a USB interface. It can capture up to 256K samples at 20MHz (80MHz with overclock), and is compatible with SUMP logic analyzer client. Get one for $30 at Seeed Studio. Logic Shrimp support available here.

Logic priate, noise bofre trigger

Postby jaromir » Tue Jul 07, 2015 4:13 am

I bought Logic Pirate from Seeed Studio. It works, but one thing is unexpected to me - noise before trigger.
When I ground input 0 and hit record on OLS, I can see noise before time zero:

After zoom-in, I can see regular square wave

The same goes when using the internal test signal and setting trigger on channel one:

Triggering works as expected, but the waveform before trigger is just wrong.
I assume trying to run UART analysis or something would lead to a lot of garbage here.
It seems like I'm running the newest firmware https://code.google.com/p/dangerous-pro ... %2F_output

Honestly, I have no idea what's going on here. I'm long-time user of logic shrimp viewtopic.php?f=58&t=2396 and this is something I didn't expect. On logic shrimp, the same waveform looks like this:
my personal webpage - http://jaromir.xf.cz/ Update 05.06, project PIC500
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