103 lines
3.2 KiB
Python
103 lines
3.2 KiB
Python
# Add a SCD41 sensor breakout to your Galactic Unicorn to make a handy CO2 detector!
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# https://shop.pimoroni.com/products/scd41-co2-sensor-breakout
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# Press A to reset the high/low values.
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from galactic import GalacticUnicorn
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from picographics import PicoGraphics, DISPLAY_GALACTIC_UNICORN as DISPLAY
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import breakout_scd41
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from pimoroni_i2c import PimoroniI2C
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from pimoroni import BREAKOUT_GARDEN_I2C_PINS
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gu = GalacticUnicorn()
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graphics = PicoGraphics(DISPLAY)
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i2c = PimoroniI2C(**BREAKOUT_GARDEN_I2C_PINS)
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WIDTH, HEIGHT = graphics.get_bounds()
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# the range of readings to map to colours
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# https://www.kane.co.uk/knowledge-centre/what-are-safe-levels-of-co-and-co2-in-rooms
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MIN = 400
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MAX = 2000
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# pick what bits of the colour wheel to use (from 0-360°)
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# https://www.cssscript.com/demo/hsv-hsl-color-wheel-picker-reinvented/
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HUE_START = 100 # green
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HUE_END = 0 # red
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# some pen colours to use
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BLACK = graphics.create_pen(0, 0, 0)
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WHITE = graphics.create_pen(255, 255, 255)
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GREY = graphics.create_pen(20, 20, 20)
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# sets up a handy function we can call to clear the screen
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def clear():
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graphics.set_pen(BLACK)
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graphics.clear()
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# some variables to keep track of high / low readings
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highest = 0.0
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lowest = 4000.0
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# set up
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breakout_scd41.init(i2c)
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breakout_scd41.start()
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graphics.set_font("bitmap8")
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graphics.set_pen(WHITE)
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graphics.text("Waiting!", 0, 0, scale=1)
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gu.update(graphics)
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while True:
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if gu.is_pressed(GalacticUnicorn.SWITCH_A):
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# reset recorded high / low values
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highest = 0.0
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lowest = 4000.0
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if breakout_scd41.ready():
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clear()
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# read the sensor
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co2, temperature, humidity = breakout_scd41.measure()
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# update highest / lowest values
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if co2 < lowest:
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lowest = co2
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if co2 > highest:
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highest = co2
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# calculate a colour from the co2 reading
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hue = max(0, HUE_START + ((co2 - MIN) * (HUE_END - HUE_START) / (MAX - MIN)))
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# create pens with this colour (and with the high / low colours)
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CURRENT_COLOUR = graphics.create_pen_hsv(hue / 360, 1.0, 0.8)
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HIGH_COLOUR = graphics.create_pen_hsv(HUE_END / 360, 1.0, 0.8)
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LOW_COLOUR = graphics.create_pen_hsv(HUE_START / 360, 1.0, 0.8)
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# draw the text
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graphics.set_pen(CURRENT_COLOUR)
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graphics.text("CO2", 0, 0, scale=1)
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# measure the rest of the text before drawing so that we can right align it
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text_width = graphics.measure_text(f"{co2:.0f}ppm", scale=1)
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graphics.text(f"{co2:.0f}ppm", WIDTH - text_width, 0, scale=1)
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# draw a bar for the background
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graphics.set_pen(GREY)
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graphics.rectangle(0, 9, WIDTH, 10)
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# draw a bar for the current co2 level
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graphics.set_pen(CURRENT_COLOUR)
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graphics.rectangle(0, 9, int(co2 / WIDTH), 10)
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# draw a bar for the highest co2 level seen
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graphics.set_pen(HIGH_COLOUR)
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graphics.pixel(int(highest / WIDTH), 9)
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graphics.pixel(int(highest / WIDTH), 10)
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# draw a bar for the lowest co2 level seen
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graphics.set_pen(LOW_COLOUR)
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graphics.pixel(int(lowest / WIDTH), 9)
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graphics.pixel(int(lowest / WIDTH), 10)
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gu.update(graphics)
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