Micro:bit candle counter

# BBC Micro:bit IR-based candle detector and counter
# by Ido Gendel, 2025
# Hardware setup:
# 3V -> L-53P3C 940nm NPN Phototransistor -> Pin 1 and 1K resistor -> GND

from microbit import *

# 3x5 digits patterns, 0 to 9 and then "E"
digits = ["888808808808888",
          "080880080080888",
          "888008888800888",
          "888008888008888",
          "808808888008008",
          "888800888008888",
          "888800888808888",
          "888008008008008",
          "888808888808888",
          "888808888008888",
          "888800888800888"]

count = 0 # How many candles were detected
currState = 0 # Are we seeing a candle now? (0/1)
threshold = 3 # Range 1-5 inclusive, each step means 170 in raw values

def refresh(rawValue):

    image = [["0","0","0","0","0"],
             ["0","0","0","0","0"],
             ["0","0","0","0","0"],
             ["0","0","0","0","0"],
             ["0","0","0","0","0"]]

    # Draw current reading and threshold
    image[5 - threshold][1] = "3"
    value = int((rawValue / 1024) * 46)
    for n in range(5):
        temp = min(value, 9)
        image[4 - n][0] = str(temp)
        value = value - temp

    # Draw counter digit
    for i in range(15):
       image[i // 3][2 + (i % 3)] = digits[count][i]

    # Display completed image
    s = ""
    for line in image:
        s = s + "".join(line) + ":"
    display.show(Image(s[:-1]))



display.clear()
while True:
    rawValue = pin1.read_analog()
    if currState == 0:
        if (rawValue >= threshold * 170 + 85) and (count < 10):
            currState = 1
            count = count + 1
    else:
        if rawValue < threshold * 170 - 85:
            currState = 0

    refresh(rawValue)

    if button_a.was_pressed():
        threshold = threshold + 1
        if threshold > 5:
            threshold = 1

    if button_b.was_pressed():
        count = 0
        display.clear()
        sleep(200)