You always learn something!
http://www.tridimake.com/2017/05/replacing-linuxcnc-with-smoothie-milling.html?m=1
My advise is: use Grbl or TinyG for milling!
That disadvantage plus the higher price 
Same experiences here with smoothieboard as CNC Controller. To control spindle rpm w/o hall sensor M3 S254 is maximum 
The rest of this article is true. IMHO a good place to make smoothie better for cnc machines.
Well… I ended up the day by wiring a $5 Nano directly on a DB25! Super ugly but so minimalist that I like it nonetheless. Seriously: it works extremely well… and I can now pause even within a move thanks to GRBL 1.1, wow!
(detailed in two chapters I appended to my post)
LOVE the nano<>db25 hack! Make a box with integrated usb, like scart plug
@Jorge_Robles eh, I just stumbled upon this (I did not find the full sources, but the idea is there & the trivial schematic is provided in PDF). Lovely!
Spectacular
+Peter van der Walt I think it would be completely wrong to push grbl-lpc to the same all-in-one solution like smoothieware tries to target. You simply can not do everything the best!
It’s a lot easyer and faster to develop optimal firmware versions for specific problems/machines than trying to fullfill all possible needs, which inclues a lot of overhead in most cases.
Why not just use the best controller/firmware combo for the target? Could mean: Smoothieware for 3d-printing, grbl-lpc for laserengraving and Grbl or TinyG for milling (depending on the needed axis count). Nobody (except us) is swapping his controller constantly between machines 
Sure grbl-lpc is not yet ready for a “normal” user and is missing some parts yet, but there is a big potential (like more axis). And it runs on a smoothieboard 
link to follow