How to setup spindle speed feedback from TACHO?

If you have a new enough LinuxCNC version, there's a encoder velocity pin scaled in RPM (in addition to RPS). For older LinuxCNC versions, you can use the scale component

I'm on 2.7.14 but when i feed the fb-rps the fb-rpm shows as zero.

So i've added a scale and low pass to smooth things out and tuned the PID so the transient load response is reasonable. Thanks for peoples contributions. The working Hal and ini are attached. See previous comments for adding hostmot2 single physical pin encoder for hardware spindle feedback.

Notes; This is for a converted Proxxon MF-70 with LEOPARD Model LC4250 KV800 Outrunner and generic ebay brushless controller (PWM -> capacitor/resistor DAC -> 0-5V speed control), ER11 collet chuck.

[Ref.
Basic Hal - net syntax etc. , Hal - near , Hal - lowpass , Hal - scale ]