This program is designed for: *
; 1) the formation of an impulse *
; start of ultrasonic distance sensor HC-SR04, *
; 2) computing (after turning on) the arithmetic mean *
; pulse width values ECHO *
; 3) comparison of a new measurement of the pulse width ECHO *
; with its reference value. *
; In case the duration of a new pulse ECHO *
; less than the duration of the reference pulse, it is done *
; the conclusion that someone is moving along the stairs.