grbl/grbl — Issue #76: Exceeding the steps/s limit
Author: DrRob
Created: 2012-03-08 21:57:50+00:00
State: open

Hello,

I'm a visitor over from the world of ShapeOko...

I was testing my ShapeOko electronics and motors with a serial terminal connected to grbl, and noticed some odd behaviour when moving the Z axis by larger amounts at the default seek speed - brief motor stalls, corrupted settings reported by '$' (but ok after a reset), grbl resets...

The ShapeOko Z-axis has a higher resolution than X and Y, and because some folks are using stepper driver boards that share microstepping settings with all three axes, the Z axis ends up with $2=2560. Since $5=1100 to get a decent speed for X and Y, the steps per second on the Z axis is very high at maximum seek speed (~46933 steps/s by my calculations). Is this likely to be the cause of the odd behaviour? I'm imagining interrupts firing faster than an interrupt routine can service them...

What's the steps-per-second limit? What's likely to happen if steps per second is too high? Lost steps? Grbl garbled? Blue smoke? Higgs Boson particles?

Thanks,
Rob.