from machine import Pin
import time

p4 = Pin(4, Pin.IN, Pin.PULL_UP)

for i in range(3): 
    print("第",i+1,"次循环结果：")
    print("上拉值:", p4.value())
    time.sleep(1)  
    p4 = Pin(4, Pin.IN, Pin.PULL_DOWN)
    print("下拉值:", p4.value())
    time.sleep(1)  
    p4 = Pin(4, Pin.IN, Pin.PULL_UP)