Quote Originally Posted by richard View Post
you sketch is incorrect...

I used this guys design.

https://hackaday.com/wp-content/uplo...uncing-sch.png


His explanation is here:

https://hackaday.com/2015/12/09/embe...uttons-part-i/


I've seen this design in other places. The 3rd resistor is to prevent the input pin from floating.