add co2 example

micropython/examples/stellar_unicorn/README.md

@@ -19,10 +19,10 @@
   - [Exchange Ticker](#exchange-ticker)
   - [HTTP Text](#http-text)
   - [Weather](#weather)
-- [NumPy examples](#numpy-examples)
+- [NumPy Examples](#numpy-examples)
 - [Other Examples](#other-examples)
+  - [CO2](#co2)
   - [Launch (Demo Reel)](#launch-demo-reel)
-- [Other Resources](#other-resources)
 
 ## About Stellar Unicorn
 
@@ -155,7 +155,7 @@ Requires `logging.mpy` and `tinyweb` from [micropython/examples/common](../../ex
 
 Display current weather data from the [Open-Meteo](https://open-meteo.com/) weather API.
 
-## NumPy examples
+## NumPy Examples
 
 [numpy](numpy)
 
@@ -163,16 +163,16 @@ The examples in the folder use `numpy`-like array functions contained in the `ul
 
 ## Other Examples
 
+### CO2
+
+[co2.py](co2.py)
+
+Add a [SCD41 sensor breakout](https://shop.pimoroni.com/products/scd41-co2-sensor-breakout) to make an carbon dioxide detector. Press A, B and C to switch between modes.
+
+This examples uses a custom tiny bitmap font, find 3x5.bitmapfont in [fonts](../../fonts) and copy it to your Pico W.
+
 ### Launch (Demo Reel)
 
 [launch](launch)
 
 If you want to get the demo reel that Stellar Unicorn ships with back, copy the contents of this `launch` folder to your Pico W.
-
-## Other Resources
-
-Here are some cool Stellar Unicorn community projects and resources that you might find useful / inspirational! Note that code at the links below has not been tested by us and we're not able to offer support with it.
-
-- :link: [Green Energy Display with Stellar Unicorn](https://www.hackster.io/andreas-motzek/clock-and-green-energy-display-with-stellar-unicorn-641dcb)
-- :link: [stellar-emoji-react - paint emojis from a computer, phone or tablet](https://github.com/chriscareycode/stellar-unicorn/tree/main/stellar-emoji-react)
-- :link: [stellar-paste - paste images from the clipboard to Stellar Unicorn](https://github.com/chriscareycode/stellar-unicorn/tree/main/stellar-paste)

micropython/examples/stellar_unicorn/co2.py

@@ -0,0 +1,104 @@
+# Add a SCD41 sensor breakout to your Stellar Unicorn to make a handy CO2 detector!
+# https://shop.pimoroni.com/products/scd41-co2-sensor-breakout
+# Press A for CO2, B for temperature and C for humidity
+# This example uses a custom tiny font - find 3x5.bitmapfont in pimoroni-pico/fonts
+
+from stellar import StellarUnicorn
+from picographics import PicoGraphics, DISPLAY_STELLAR_UNICORN as DISPLAY
+import breakout_scd41
+from pimoroni_i2c import PimoroniI2C
+from pimoroni import BREAKOUT_GARDEN_I2C_PINS
+
+su = StellarUnicorn()
+graphics = PicoGraphics(DISPLAY)
+i2c = PimoroniI2C(**BREAKOUT_GARDEN_I2C_PINS)
+
+# 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)
+
+# some other variables to keep track of stuff
+mode = "co2"
+flashy_light = False
+
+
+# sets up a handy function we can call to clear the screen
+def clear():
+    graphics.set_pen(BLACK)
+    graphics.clear()
+
+
+# set up
+breakout_scd41.init(i2c)
+breakout_scd41.start()
+
+graphics.set_font(open("3x5.bitmapfont", "rb").read())
+graphics.set_pen(WHITE)
+graphics.text("WAIT", 0, 0, scale=1)
+su.update(graphics)
+
+while True:
+
+    if su.is_pressed(StellarUnicorn.SWITCH_A):
+        mode = "co2"
+    if su.is_pressed(StellarUnicorn.SWITCH_B):
+        mode = "temp"
+    if su.is_pressed(StellarUnicorn.SWITCH_C):
+        mode = "humidity"
+
+    if breakout_scd41.ready():
+        clear()
+
+        # read the sensor
+        co2, temperature, humidity = breakout_scd41.measure()
+
+        # calculate a colour from the co2 reading
+        hue = max(0, HUE_START + ((co2 - MIN) * (HUE_END - HUE_START) / (MAX - MIN)))
+
+        # draw the border and background
+        graphics.set_pen(graphics.create_pen_hsv((hue / 360), 1.0, 0.8))
+        graphics.clear()
+        graphics.set_pen(graphics.create_pen_hsv((hue / 360), 1.0, 0.2))
+        graphics.rectangle(1, 1, 14, 14)
+
+        graphics.set_pen(WHITE)
+        if mode == "co2":
+            # draw the co2 level
+            co2_string = str(co2)
+            if co2 < 999:
+                graphics.text(f"{co2:.0f}", 2, 2, scale=1, fixed_width=True)
+            else:
+                graphics.text(f"{co2_string[0]}", 1, 2, scale=1, fixed_width=True)
+                graphics.text(f"{co2_string[1]}K", 7, 2, scale=1, fixed_width=True)
+                graphics.pixel(5, 6)
+
+            graphics.text("PPM", 3, 9, scale=1)
+
+        if mode == "temp":
+            # draw the temperature
+            graphics.text("T:", 2, 2, scale=1)
+            graphics.text(f"{temperature:.0f}°", 2, 8, scale=1, fixed_width=True)
+
+        if mode == "humidity":
+            # draw the temperature
+            graphics.text("H:", 2, 2, scale=1)
+            graphics.text(f"{humidity:.0f}%", 2, 8, scale=1, fixed_width=True)
+
+        # flash the top right pixel to show the sensor's been read
+        if flashy_light is False:
+            graphics.pixel(15, 0)
+            flashy_light = True
+        else:
+            flashy_light = False
+
+        su.update(graphics)