from machine import Pin,ADC,PWM

adc=ADC(Pin(35))
adc.atten(ADC.ATTN_11DB)
adc.width(ADC.WIDTH_12BIT)
pwm=PWM(Pin(21))
pwm.freq(50)
def map(x,in_min,in_max,out_min,out_max):
   return int((x-in_min)*(out_max-out_min)/(in_max-in_min)+out_min)

while True:
  adc_value = adc.read()
  pwm.duty(map(adc_value,0,4095,25,125))
  volts=(3.3*adc_value)/4095
  voltage="Voltage is {:0.2f} and raw value is {}"
  print(voltage.format(volts,adc_value),end='\r')