CO2 monitor using Pimoroni Wireless Plasma Kit + Adafruit SCD40, MicroPython 1.20.3

main.py

# https://github.com/pimoroni/pimoroni-pico/blob/main/micropython/examples/plasma_stick/co2.py
# https://docs.micropython.org/en/latest/library/rp2.html#rp2.bootsel_button
# https://github.com/pimoroni/phew/blob/v0.0.3/phew/__init__.py

import time
import plasma
from plasma import plasma_stick
from machine import Pin
import breakout_scd41 as scd
from pimoroni_i2c import PimoroniI2C
import rp2
import network
import random

wlan = network.WLAN(network.AP_IF)

NUM_LEDS = 50

YELLOW_START = 50
YELLOW_END = 70

GREEN_START = 95
GREEN_END = 145

RED_START = 345
RED_END = 375

HUE_START = YELLOW_START
HUE_END = YELLOW_END
SPEED = 0.3  # bigger = faster (harder, stronger)

VALUE = 0.8
LAST_TIME = time.ticks_ms()

def hex_to_rgb(hex):
    # converts a hex colour code into RGB
    h = hex.lstrip('#')
    r, g, b = (int(h[i:i + 2], 16) for i in (0, 2, 4))
    return r, g, b

# set up the Pico W's onboard LED
pico_led = Pin('LED', Pin.OUT)

# set up the WS2812 / NeoPixel™ LEDs
led_strip = plasma.WS2812(NUM_LEDS, 0, 0, plasma_stick.DAT, color_order=plasma.COLOR_ORDER_RGB)

# start updating the LED strip
led_strip.start()

# set up I2C
i2c = PimoroniI2C(plasma_stick.SDA, plasma_stick.SCL)

# set up SCD41 breakout
scd.init(i2c)
scd.start()
co2 = 600

distance = 0.0
direction = SPEED
while True:
    if scd.ready():
        co2, temperature, humidity = scd.measure()
        wlan.active(False)
        wlan.config(essid=f"CO2: {str(int(co2))}", password=str(random.randrange(10000000, 99999999)))
        wlan.active(True)

    for i in range(NUM_LEDS):
        if co2 < 600:
            HUE_START = GREEN_START
            HUE_END = GREEN_END
        elif co2 >= 800:
            HUE_START = RED_START
            HUE_END = RED_END
        else:
            HUE_START = YELLOW_START
            HUE_END = YELLOW_END

        # generate a triangle wave that moves up and down the LEDs
        j = max(0, 1 - abs(distance - i) / (NUM_LEDS / 3))
        hue = HUE_START + j * (HUE_END - HUE_START)

        if time.ticks_ms() - LAST_TIME > 350:
            if rp2.bootsel_button():
                VALUE = VALUE - 0.1
                if VALUE <= 0.1:
                    VALUE = 0.8
                LAST_TIME = time.ticks_ms()

        led_strip.set_hsv(i, hue / 360, 1.0, VALUE)

    # reverse direction at the end of colour segment to avoid an abrupt change
    distance += direction
    if distance > NUM_LEDS:
        direction = - SPEED
    if distance < 0:
        direction = SPEED

    time.sleep(0.01)