import time
from machine import ADC, Pin, idle
from neopixel import NeoPixel

LEDS = 20
OFFSET = 1449

adc0 = ADC(Pin(10))
np = NeoPixel(Pin(15), LEDS)
np.fill((0,0,0))
np.write()


class IIRLowPassShift:
    def __init__(self, shift: int, initial: int=0, offset: int=0):
        self.shift = shift
        self.y = initial
        self.offset = offset
 
    def update(self):
        x = adc0.read_u16()
        self.y = self.y + ((x - self.y) >> self.shift)
        return max(0, self.y - self.offset)


low_pass = IIRLowPassShift(4, offset=OFFSET)


while True:
    value = low_pass.update() / 65536 * LEDS
    value, fraction = divmod(value, 1)
    # print(value, fraction)
    for i in range(LEDS):
        if value > i:
            np[i] = (255, 0, 0)
        elif fraction:
            np[i] = (int(fraction * 255), 0, 0)
            fraction = 0
        else:    
            np[i] = (0, 0, 0)
        
    np.write()
    # time.sleep_ms(1)
    idle()