Apparent crashes using 3.1-3G5D firmware

[Cliff L. Biffle]

I've installed the 3G5D firmware provided by RepG (MB1.2 v3.1).

Now sometimes, during a build, my bot freaks out.  If this happens during motion, the steppers keep going at a constant rate, and it'll draw a straight line into infinity if I don't reset it.  I'm not spectacularly familiar with the innards of the firmware, but this is the sort of thing I'd expect if a main control loop went off into hyperspace, leaving an interrupt-driven stepper sequencing routine running.

I've had a few successful builds, but my failure rate is around 50% at this point.  Certain Skeinforge plugins, curiously, seem to exacerbate it.  Limit, in particular -- which is unfortunate, because without Limit, SF35 was trying to drive my Z axis so fast that I was losing steps.  (Without Limit I've only seen one crash.)

I'm not sure if it's related, but I also see small motion control glitches.  In particular, when the bot is drawing a line parallel to the Y axis (e.g. during a raft or fill), the X axis steps once each time the extruder crosses Y=0.  On some lines, the Z axis steps too, and it's held the whole time, suggesting that the firmware is attempting to interpolate a very small Z move into a horizontal motion.  This smells like numerical precision issues in an interpolation routine to me, but again, I haven't dug into it.

While it's possible that my 3G5D hardware is to blame, it passes electrical tests.

Has anyone else encountered these issues?

-Cliff L. Biffle