A glitch in data is usually identified by a relatively tiny, and unintentional, pulse in voltage as shown below. This can occur due to radiated noise caused by nearby electronics, noise in the circuit itself, extremely slow rise/fall times in the digital data, poor PCB layout, and many other reasons.
Glitches can cause protocol analyzers to incorrectly interpret the underlying data. Because of this, Saleae Logic offers a software glitch filter to "hide" unwanted glitches from being visible. Please be careful - this doesn't mean the glitches have gone away. It simply means we are "hiding" them from view so that our protocol analyzers can properly do their job. Many times, when a protocol analyzer doesn't seem to be decoding properly, looking for glitches to filter can be a useful first step to debug the issue.
To learn more about our software glitch filter, see our user guide on it below.
Many times, an engineer will record data that may contain unwanted noise in the recording. These glitches can really confuse our protocol analyzers and hinder its ability to decode the underlying data. Enabling the software glitch filter doesn't solve the glitch issue, but instead, helps the protocol analyzer decode the data and do its job properly.
Start a simulation capture of digital data for a single capture (no protocol analyzers need to be added). Note the general length of time between digital transitions in the recording.
Look for a pair of digital transitions with a small amount of time between them compared to the rest. We will try to filter this pair.
Now set the Glitch Filter to a time that is slightly above the time you found in the step above. Afterwards, notice that the digital transition pair you found previously has now been "filtered" or "hidden".
In summary, all pairs of digital transitions that occur within the time specified in Glitch Filter settings will be hidden by our glitch filter.