from  machine import  Pin,ADC,Timer
LDR=ADC(Pin(15))
GAMMA=0.7
RL10=50
def fun(tim):
    global GAMMA
    global RL10
    analogValue=LDR.read()
    voltage=analogValue/4096.*5
    resistance=2000*voltage/(1-voltage/5)
    lux=pow(RL10*1e3*pow(10,GAMMA)/resistance,(1/GAMMA))
    print(lux)
tim=Timer(1)
tim.init(period=500,mode=Timer.PERIODIC,callback=fun)