C3D Spindle RPM control issues

I have my min/max RPM values ($30/$31) set in GRBL. I had to do this with the console as the Raspberry Pi build doesn’t appear to be updated (that’s fine).

When I issue M3S24000 I get full speed.

But the lower end doesn’t seem to be working. M3S15000 brings me to around 8000RPM. M3S8000, the spindle turns off.

Anyone run into this?

It’s confusing how grbl handles this but I believe when you set $30=8000, essentially that means calling s8000 m3 tells the spindle you want 0 rpm. You’ve mapped s8000 to the min speed this throws off the scaling. I find it works best to leave that number at 0 or 1

Sweet, $31=0 did the trick!

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