Servo tuning & keyboard repeat: a warning!

Something to keep in mind when you think you're going to lose your mind!

I spent a number of hours yesterday working on servo tuning and I wasted time with something I didn't expect.  I kept seeing glitching in my f-error that I couldn't explain.  After checking for mechanical issues (belt slip, loose mounts, etc.), on a whim I happened to try some moves from the MDI - and surprise, no more random glitching!

Long story short, it turns out key repeat was causing problems.  It's easy to 'fix' by issuing an xset -r command to disable key repeat.  There are other approaches as well, a forum search will turn up a few threads.

Here's what I was seeing with key repeat enabled.  You can see the spikes in the velocity command.  It really wreaks havoc on the f-error.
 

And when it's disabled, no more random glitches.  Terrible servo tuning, but no glitches!
 

tommylight wrote:

Seeing this i have to consider myself really lucky, even once i had this issue it was in my shop during some random testing!
Thank you for reporting this, have to keep in mind in case i ever see such f-error.

Think it's worth pinning or adding to one of the servo tuning guides on the wiki?