Hi I have the following as the one I have been using...is there other good ideas or better practices...likey may be pulled to different voltage or dirrerent way of providing reference voltage...and yes easy to calculate..
The traditional Schmidt Trigger toggles at 1/3 and 2/3 Vcc and that gives it much better noise immunity than the circuit you presented. I cast a wary eye on your circuit because it might false trigger a lot more than the traditional style.