Add optional SCD41 CO2 sensor to Enviro Indoor

Author: MichaelBell

enviro/boards/indoor.py

@@ -1,9 +1,18 @@
 import math
+import time
 from breakout_bme68x import BreakoutBME68X
 from breakout_bh1745 import BreakoutBH1745
 
-from enviro import i2c
+from enviro import i2c, i2c_devices
 
+# Detect whether an SCD41 CO2+ sensor is connected
+have_scd41 = 98 in i2c_devices
+if have_scd41:
+  import breakout_scd41
+
+  breakout_scd41.init(i2c)
+  breakout_scd41.start()
+  
 bme688 = BreakoutBME68X(i2c, address=0x77)
 
 bh1745 = BreakoutBH1745(i2c)
@@ -54,14 +63,31 @@ def get_sensor_readings(seconds_since_last):
 
   bh1745.measurement_time_ms(160)
   r, g, b, c = bh1745.rgbc_raw()
+  
+  co2 = 0
+  if have_scd41:
+    retries = 25
+    while retries > 0 and not breakout_scd41.ready():
+      time.sleep(0.2)
+      retries -= 1
+
+    if retries != 0:
+      co2, temp_scd, hum_scd = breakout_scd41.measure()
+       
+      # Prefer the SCD41 temperature as it is further from the potentially warm Pico
+      temperature = round(temp_scd, 2)
 
   from ucollections import OrderedDict
-  return OrderedDict({
+  d = OrderedDict({
     "temperature": temperature,
     "humidity": humidity,
     "pressure": pressure,
     "gas_resistance": gas_resistance,
     "aqi": aqi,
     "luminance": lux_from_rgbc(r, g, b, c),
     "color_temperature": colour_temperature_from_rgbc(r, g, b, c)
-  })
+  })
+  if co2 > 0:
+    d["CO2"] = co2
+
+  return d