pico-co2-main.py

# Requires the following micropython libraries - install these to the Pi Pico with Thonny
# errno, ffilib, os, scd30, signal, ssd1306, stat
# Rename this file to "main.py" and save to the Pico so that it runs automatically on power on.

import time
import math
from machine import Pin, I2C
from machine import WDT
from scd30 import SCD30
from ssd1306 import SSD1306_I2C

# Initialise the two switches (not currently used)
sw1 = Pin(18, Pin.IN, None)
sw2 = Pin(19, Pin.IN, None)

# Set the RGB LED pins
led_rgb_r = Pin(2, Pin.OUT)
led_rgb_g = Pin(3, Pin.OUT)
led_rgb_b = Pin(4, Pin.OUT)

# Function to set the color of the RGB
def led_set_rgb(r, g, b):
    led_rgb_r.value(r)
    led_rgb_g.value(g)
    led_rgb_b.value(b)
    
# Set the RGB LED to white during initialisation
led_set_rgb(1,1,1)

# Utility function to convert a second count to hours:minutes:seconds
def secondsToString(s):
    hour = math.floor(s/3600)
    minute = math.floor((s-(hour*3600))/60)
    second = s - (60 * minute) - (3600 * hour);
    return '{:02d}:{:02d}:{:02d}'.format(hour, minute, second)

# Initialise the i2c interface
i2c=I2C(0, sda=Pin(12), scl=Pin(13), freq=400000)

# Initialise the SCD30 sensor
scd30 = SCD30(i2c, 0x61)
scd30.set_measurement_interval(2)
scd30.start_continous_measurement()

# Wait for 1.5 seconds to ensure the OLED is ready
time.sleep(1.5)

# Initialise the OLED screen
oled = SSD1306_I2C(128, 64, i2c)
oled.show()

# Store the start time to use for deriving the uptime
start = time.time()

# Initialise the Watchdog timer timout (5 seconds)
wdt = WDT(timeout=5000)

# A callback to handle the button presses
def switch_pressed(p):
    print('pin change', p)

# Set up the two switches with callback
sw1.irq(trigger=Pin.IRQ_RISING | Pin.IRQ_FALLING, handler=switch_pressed)
sw2.irq(trigger=Pin.IRQ_RISING | Pin.IRQ_FALLING, handler=switch_pressed)

# The main loop
while True:
    # Reset the watchdog timer
    wdt.feed()
    # If the sensor has a value...
    if scd30.get_status_ready():
        # Read the sensor data
        m = scd30.read_measurement()
        if m is not None:
            # Print the sensor data to the screen
            oled.fill(0);
            oled.text("CO2: " + ('%.2f' % m[0]) + " ppm", 0, 0)
            oled.text("Temp: " + ('%.2f' % m[1]) + " C", 0, 10)
            runtime = (time.time() - start)
            oled.text("uptime: " + secondsToString(runtime), 0, 50)
            oled.show()
            # Set the RGB LED
            # Green: 0 - 599 ppm
            # Blue : 600-799 ppm
            # Red  : 800+ ppm
            if(m[0] <= 600):
                led_set_rgb(0,1,0)
            elif (m[0] <= 800):
                led_set_rgb(0,0,1)
            else:
                led_set_rgb(1,0,0)
        # Wait 2 seconds until the next reading is available
        time.sleep(2)
    else:
        # Wait 0.2 seconds and then try again
        time.sleep(0.2)