CO2 monitor using Adafruit Trinkey QT2040 + SCD-40 + ST25DV16K, CircuitPython 8.x

main.py

# SPDX-FileCopyrightText: 2021 Carter Nelson for Adafruit Industries
# SPDX-License-Identifier: MIT

import time
import board
import adafruit_scd4x
import neopixel
import adafruit_24lc32

## https://github.com/Neradoc/circuitpython-st25dv
class ST25DV16(adafruit_24lc32.EEPROM_I2C):
    def __init__(self, i2c_bus, address=0x53, write_protect=False, wp_pin=None):
        from adafruit_bus_device.i2c_device import I2CDevice
        self._i2c = I2CDevice(i2c_bus, address)
        adafruit_24lc32.EEPROM.__init__(self, adafruit_24lc32.const(0x800), write_protect, wp_pin)

## https://github.com/Neradoc/circuitpython-st25dv
def payload_text(text, language='en'):
    text_data = text.encode()
    language_code = language.encode()
    type_length = len(language_code) + 1
    text_field_length = len(text_data) + type_length
    rfid_payload = bytes([0xD1, 0x01, text_field_length]) + b"T" + bytes([len(language_code)]) + language_code + text_data
    return bytes([0xE1, 0x40, 0x40, 0x05]) + bytes([0x03, len(rfid_payload)]) + rfid_payload + b"\xFE"

# setup stuff
i2c = board.STEMMA_I2C()  # For using the built-in STEMMA QT connector on a microcontroller
scd = adafruit_scd4x.SCD4X(i2c)
scd.start_periodic_measurement()
pixel = neopixel.NeoPixel(board.NEOPIXEL, 1)
eeprom = ST25DV16(i2c)

# init time tracking and heartbeat
last_beat = time.monotonic()
beat_color = 0xFFFF00
beat_brightness = 0.1
beat_rate = 1

# loop forever!
while True:
    current_time = time.monotonic()

    # data
    if scd.data_ready:
        CURR_CO2 = scd.CO2
        CO2_DATA = "CO2: {}".format(CURR_CO2)
        RFID_DATA = payload_text(CO2_DATA)
        beat_color = 0xFFFF00
        beat_brightness = 1.0

        if CURR_CO2 < 600:
            beat_color = 0x00FF00
        elif CURR_CO2 >= 800:
            beat_color = 0xFF0000
        
        print(CO2_DATA)
        try:
            eeprom[0:len(RFID_DATA)] = RFID_DATA
        except:
            pass

    # heart beat
    if current_time - last_beat > beat_rate:
        r,g,b = pixel[0]
        if r or g or b:
            pixel.fill(0)
        else:
            pixel.brightness = beat_brightness
            pixel.fill(beat_color)
            beat_brightness = 0.1

        last_beat = current_time