reflex game
from machine import Pin
import time
import random

beeper = Pin(13, Pin.OUT)
pin1 = Pin(15,Pin.IN,Pin.PULL_UP)

T0 = 0
T1 = 0
flag = 0

def Button15(pin1):
    global T1, flag
    T1 = time.ticks_us()
    flag = 1    

# options are RISING, FALLING, LOW_LEVEL, HIGH_LEVEL
pin1.irq(trigger=Pin.IRQ_FALLING, handler=Button15)


while(1):
    beeper.value(0)
    flag = 0
    while(flag == 0):
        pass
    print('Starting:  4..7 seconds later')
    dT = random.random() * 4 + 3
    time.sleep(dT)
    flag = 0
    beeper.value(1)
    T0 = time.ticks_us()
    while(flag == 0):
        pass
    beeper.value(0)
    Reflex = T1 - T0
    print('Reflex Time(us) = ',T1-T0)