Servo confusion

[Ramius]

First I love my Saleae logic analyzer and just ran into something that I am confused about.
I was looking at the pulses being sent to a R/C servo both with a "regular" scope and the logic analyzer and they are very different.
One the scope there is only one square wave of 1.5 ms occurring every 20ms.
However, the logic analyzer does not show this same pattern!
The logic analyzer is showing multiple pulses of different widths. (Please see attached)
Would you have any ideas as to what I am doing wrong?

Thanks, Ed

[ardhuru]

Ed, your scope readings are almost certainly the right ones. Coincidentally, I too was playing around with some servos, and checked out the waveforms on a scope and an analyzer, both were pretty consistent for a given setting.

If you have the Pickit2, why dont you confirm this by using the analyzer feature in the Pickit2 software? Thats the only analzer I have and its not let me down yet.

Anand.

[languer]

The scope is real-time analog signal and the logic analyzer is sampled digital signal. Which means if you have "glitches" of any kind that trigger the digital logic, you will see them as "real" signals. Also it means you have to be mindful of digital "artifacts".

Did you try lowering the sample rate from 24MHz to say, 1MHz? And lowering the samples from 100M to say 10M? Also make sure your grounds are very good on the Logic Analyzer. BTW, I have a Logic device from Saleae - awesome tool - haven't really have any issues with it.

[Ramius]

Thanks to all!
Turned out that this is their sample "sample" waveform. The USB connection was overwritten by my camera installation evident by the word "disconnected" at the top (time for new glasses)! Yes, I completely agree, the Saleae is an awesome tool and is Saleae as a company. There was a post I read where someone claimed their device stopped working and Saleae quickly sent a replacement / exchange without all the typical proof of purchase requirements! Thanks again, you guys are the best! Sincerely, Ed