Best practice for spindle accelerating/decelerating in velocity mode

Hi people!

what is the best practice for accelerating (and more importantly, decelerating) the hm2 (MESA card 7i95) stepgen in velocity mode?

I ask because I found a parameter like this - hm2_7i95.0.stepgen.05.maxaccel - but it works a little bit strange: 
1) if I want to change spindle speed from 0 to 1000rpm - acceleration from stepgen works fine without problem (m3 S1000).
2) if I want to change spindle speed from 1000rpm to 1rpm - deceleration works also fine without problem (M3 S1000 then S1).
3) but if I want to change spindle speed from 1000rpm to 0rpm - the spindle stops immediately without any deceleration (M3 S1000 then S0).

Thank you in advance!
 

Because when you set spindle speed to 0, the stepgen turns off.  This results in your drive seeing an immediate command and thus no ramp-down.

The problem is caused by your stepgen.N.enable pin being connected to some pin (likley spindle.N.on) that shuts off when the spindle is turned off. 

This issue has been reported on GitHub, and I believe PnCconf has been (or is going to be) changed so the stepgen spindle connections are more appropriate.  Same with Mesact.

Try connecting stepgen enable to something like machine-is-on.  The stepgen will remain enabled during the desired ramp-down and that's when you can start seeing a changed with max_accel value tuning.