Merge pull request #792 from pimoroni/patch/co2-examples

SCD41: update examples

micropython/examples/breakout_scd41/scd41_demo.py

@@ -1,12 +1,9 @@
+import breakout_scd41
+from pimoroni_i2c import PimoroniI2C
+from pimoroni import BREAKOUT_GARDEN_I2C_PINS  # or PICO_EXPLORER_I2C_PINS or HEADER_I2C_PINS
 import time
 
-import pimoroni_i2c
-import breakout_scd41
-
-PINS_BREAKOUT_GARDEN = {"sda": 4, "scl": 5}
-PINS_PICO_EXPLORER = {"sda": 20, "scl": 21}
-
-i2c = pimoroni_i2c.PimoroniI2C(**PINS_PICO_EXPLORER)
+i2c = PimoroniI2C(**BREAKOUT_GARDEN_I2C_PINS)  # or PICO_EXPLORER_I2C_PINS or HEADER_I2C_PINS
 
 breakout_scd41.init(i2c)
 breakout_scd41.start()

micropython/examples/plasma2040/co2.py

@@ -0,0 +1,71 @@
+import plasma
+from plasma import plasma2040
+import breakout_scd41 as scd
+from pimoroni_i2c import PimoroniI2C
+from pimoroni import RGBLED
+import time
+
+"""
+Reads CO2 level from an SCD41 breakout...
+... and changes the LED strip an appropriate colour.
+https://shop.pimoroni.com/products/scd41-co2-sensor-breakout
+"""
+
+# set how many LEDs you have
+NUM_LEDS = 50
+
+BRIGHTNESS = 1.0
+
+# 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
+
+# Pick *one* LED type by uncommenting the relevant line below:
+# WS2812 / NeoPixel™ LEDs
+led_strip = plasma.WS2812(NUM_LEDS, 0, 0, plasma2040.DAT)
+
+# APA102 / DotStar™ LEDs
+# led_strip = plasma.APA102(NUM_LEDS, 0, 0, plasma2040.DAT, plasma2040.CLK)
+
+# set up I2C
+i2c = PimoroniI2C(plasma2040.SDA, plasma2040.SCL)
+
+# set up onboard LED
+led = RGBLED(plasma2040.LED_R, plasma2040.LED_G, plasma2040.LED_B)
+
+led.set_rgb(0, 0, 0)
+
+# Start updating the LED strip
+led_strip.start()
+
+# set up SCD41 breakout
+scd.init(i2c)
+scd.start()
+
+print("Waiting for SCD41 to be ready")
+
+while True:
+    if scd.ready():
+        co2, temperature, humidity = scd.measure()
+        print(f"""
+CO2:         {co2} ppm
+Temperature: {temperature:.2f} °C
+Humidity:    {humidity:.2f} %""")
+
+        # calculates a colour
+        hue = max(0, HUE_START + ((co2 - MIN) * (HUE_END - HUE_START) / (MAX - MIN)))
+
+        # set the leds
+        for i in range(NUM_LEDS):
+            led_strip.set_hsv(i, hue / 360, 1.0, BRIGHTNESS)
+
+        # flash the onboard LED so you can tell when the script is running
+        led.set_rgb(0, 255, 0)
+        time.sleep(0.05)
+        led.set_rgb(0, 0, 0)

micropython/examples/plasma_stick/co2.py

@@ -48,7 +48,7 @@ Temperature: {temperature:.2f} °C
 Humidity:    {humidity:.2f} %""")
 
         # calculates a colour
-        hue = HUE_START + ((co2 - MIN) * (HUE_END - HUE_START) / (MAX - MIN))
+        hue = max(0, HUE_START + ((co2 - MIN) * (HUE_END - HUE_START) / (MAX - MIN)))
 
         # set the leds
         for i in range(NUM_LEDS):