from machine import Pin, ADC
import time

p15 = Pin(4, Pin.IN)

while True:
    if p15.value():
        print("注意：有磁性物质靠近...")
        print("p15:{}".format(p15.value()))
    else:
        print("无磁性物质靠近...")
        print("p15:{}".format(p15.value()))
    time.sleep(1)