Merge pull request #700 from pimoroni/examples/galactic-co2

Galactic: add CO2 breakout example

micropython/examples/galactic_unicorn/README.md

@@ -4,6 +4,7 @@
 - [Galactic Unicorn and PicoGraphics](#galactic-unicorn-and-picographics)
 - [Examples](#examples)
   - [Clock](#clock)
+  - [CO2](#co2)
   - [Eighties Super Computer](#eighties-super-computer)
   - [Feature Test](#feature-test)
   - [Feature Test With Audio](#feature-test-with-audio)
@@ -13,6 +14,7 @@
   - [Rainbow](#rainbow)
   - [Scrolling Text](#scrolling-text)
 - [Wireless Examples](#wireless-examples)
+  - [Cheerlights](#cheerlights)
   - [Cheerlights History](#cheerlights-history)
   - [Galactic Paint](#galactic-paint)
 - [Other Examples](#other-examples)
@@ -45,6 +47,12 @@ The easiest way to start displaying cool stuff on Galactic Unicorn is using our
 
 Clock example with (optional) NTP synchronization. You can adjust the brightness with LUX + and -, and resync the time by pressing A.
 
+### CO2
+
+[co2.py](co2.py)
+
+Add a [SCD41 sensor breakout](https://shop.pimoroni.com/products/scd41-co2-sensor-breakout) to make an unsubtle carbon dioxide detector. Press A to reset the high/low values.
+
 ### Eighties Super Computer
 
 [eighties_super_computer.py](eighties_super_computer.py)
@@ -100,18 +108,21 @@ Display scrolling wisdom, quotes or greetz. You can adjust the brightness with L
 
 ## Wireless Examples
 
-These examples need `WIFI_CONFIG.py` (from the `common` directory) to be saved to your Pico W. Open up `WIFI_CONFIG.py` in Thonny to add your wifi details (and save it when you're done).
+These examples require `WIFI_CONFIG.py` and `network_manager.py` (from the `common` directory) to be saved to your Pico W. Open up `WIFI_CONFIG.py` in Thonny to add your wifi details (and save it when you're done).
 
 - [micropython/examples/common](../../examples/common)
 
+### Cheerlights
+[cheerlights.py](cheerlights.py)
+
+Displays the most recent #Cheerlights colour. Find out more about the Cheerlights API at https://cheerlights.com/
+
 ### Cheerlights History
 
 [cheerlights_history.py](cheerlights_history.py)
 
 Updates one pixel every five minutes to display the most recent #Cheerlights colour. Discover the most popular colours over time, or use it as an avant garde (but colourful) 53 hour clock! Find out more about the Cheerlights API at https://cheerlights.com/
 
-Requires `WIFI_CONFIG.py` and `network_manager.py` from the `common` directory.
-
 You can adjust the brightness with LUX + and -.
 
 ### Galactic Paint

micropython/examples/galactic_unicorn/co2.py

@@ -0,0 +1,102 @@
+# Add a SCD41 sensor breakout to your Galactic Unicorn to make a handy CO2 detector!
+# https://shop.pimoroni.com/products/scd41-co2-sensor-breakout
+# Press A to reset the high/low values.
+
+from galactic import GalacticUnicorn
+from picographics import PicoGraphics, DISPLAY_GALACTIC_UNICORN as DISPLAY
+import breakout_scd41
+from pimoroni_i2c import PimoroniI2C
+from pimoroni import BREAKOUT_GARDEN_I2C_PINS
+
+gu = GalacticUnicorn()
+graphics = PicoGraphics(DISPLAY)
+i2c = PimoroniI2C(**BREAKOUT_GARDEN_I2C_PINS)
+
+WIDTH, HEIGHT = graphics.get_bounds()
+
+# the range of readings to map to colours
+# https://www.kane.co.uk/knowledge-centre/what-are-safe-levels-of-co-and-co2-in-rooms
+MIN = 400
+MAX = 2000
+
+# pick what bits of the colour wheel to use (from 0-360°)
+# https://www.cssscript.com/demo/hsv-hsl-color-wheel-picker-reinvented/
+HUE_START = 100  # green
+HUE_END = 0  # red
+
+# some pen colours to use
+BLACK = graphics.create_pen(0, 0, 0)
+WHITE = graphics.create_pen(255, 255, 255)
+GREY = graphics.create_pen(20, 20, 20)
+
+
+# sets up a handy function we can call to clear the screen
+def clear():
+    graphics.set_pen(BLACK)
+    graphics.clear()
+
+
+# some variables to keep track of high / low readings
+highest = 0.0
+lowest = 4000.0
+
+# set up
+breakout_scd41.init(i2c)
+breakout_scd41.start()
+
+graphics.set_font("bitmap8")
+graphics.set_pen(WHITE)
+graphics.text("Waiting!", 0, 0, scale=1)
+gu.update(graphics)
+
+while True:
+    if gu.is_pressed(GalacticUnicorn.SWITCH_A):
+        # reset recorded high / low values
+        highest = 0.0
+        lowest = 4000.0
+
+    if breakout_scd41.ready():
+        clear()
+        # read the sensor
+        co2, temperature, humidity = breakout_scd41.measure()
+
+        # update highest / lowest values
+        if co2 < lowest:
+            lowest = co2
+        if co2 > highest:
+            highest = co2
+
+        # calculate a colour from the co2 reading
+        hue = max(0, HUE_START + ((co2 - MIN) * (HUE_END - HUE_START) / (MAX - MIN)))
+
+        # create pens with this colour (and with the high / low colours)
+        CURRENT_COLOUR = graphics.create_pen_hsv(hue / 360, 1.0, 0.8)
+        HIGH_COLOUR = graphics.create_pen_hsv(HUE_END / 360, 1.0, 0.8)
+        LOW_COLOUR = graphics.create_pen_hsv(HUE_START / 360, 1.0, 0.8)
+
+        # draw the text
+        graphics.set_pen(CURRENT_COLOUR)
+        graphics.text("CO2", 0, 0, scale=1)
+        # measure the rest of the text before drawing so that we can right align it
+        text_width = graphics.measure_text(f"{co2:.0f}ppm", scale=1)
+        graphics.text(f"{co2:.0f}ppm", WIDTH - text_width, 0, scale=1)
+
+        # draw a bar for the background
+        graphics.set_pen(GREY)
+        graphics.rectangle(0, 9, WIDTH, 10)
+
+        # draw a bar for the current co2 level
+        graphics.set_pen(CURRENT_COLOUR)
+        graphics.rectangle(0, 9, int(co2 / WIDTH), 10)
+
+        # draw a bar for the highest co2 level seen
+        graphics.set_pen(HIGH_COLOUR)
+        graphics.pixel(int(highest / WIDTH), 9)
+        graphics.pixel(int(highest / WIDTH), 10)
+
+        # draw a bar for the lowest co2 level seen
+        graphics.set_pen(LOW_COLOUR)
+        graphics.pixel(int(lowest / WIDTH), 9)
+        graphics.pixel(int(lowest / WIDTH), 10)
+
+        gu.update(graphics)