Merge pull request #9 from caternuson/iss2_mcp2221

Refinements for MCP2221

Author: ladyada

adafruit_scd30.py

@@ -61,11 +61,11 @@ def __init__(self, i2c_bus, ambient_pressure=0, address=SCD30_DEFAULT_ADDR):
         self._buffer = bytearray(18)
         self._crc_buffer = bytearray(2)
 
-        self.reset()
-
+        # set continuous measurement interval in seconds
         self.measurement_interval = 2
+        # activate automatic self-calibration
         self.self_calibration_enabled = True
-        # sets ambient pressure and starts continuous measurements
+        # trigger continuous measurements with optional ambient pressure compensation
         self.ambient_pressure = ambient_pressure
 
         # cached readings
@@ -76,7 +76,7 @@ def __init__(self, i2c_bus, ambient_pressure=0, address=SCD30_DEFAULT_ADDR):
     def reset(self):
         """Perform a soft reset on the sensor, restoring default values"""
         self._send_command(_CMD_SOFT_RESET)
-        sleep(0.030)  # not mentioned by datasheet, but required to avoid IO error
+        sleep(0.1)  # not mentioned by datasheet, but required to avoid IO error
 
     @property
     def measurement_interval(self):
@@ -108,6 +108,8 @@ def self_calibration_enabled(self):
     @self_calibration_enabled.setter
     def self_calibration_enabled(self, enabled):
         self._send_command(_CMD_AUTOMATIC_SELF_CALIBRATION, enabled)
+        if enabled:
+            sleep(0.01)
 
     @property
     def data_available(self):
@@ -196,7 +198,7 @@ def temperature(self):
     def relative_humidity(self):
         """Returns the current relative humidity in %rH.
 
-        **NOTE** Between measurements, the most recent reading will be cached and returned. """
+        **NOTE** Between measurements, the most recent reading will be cached and returned."""
         if self.data_available:
             self._read_data()
         return self._relative_humidity

examples/scd30_mcp2221test.py

@@ -0,0 +1,39 @@
+# SPDX-FileCopyrightText: 2021 by Carter Nelson, written for Adafruit Industries
+#
+# SPDX-License-Identifier: Unlicense
+import time
+import board
+import busio
+import adafruit_scd30
+
+i2c = busio.I2C(board.SCL, board.SDA)
+scd = adafruit_scd30.SCD30(i2c)
+
+# The SCD30 reset generates a hiccup on the SCL and SDA lines
+# which can end up not being handled well by different hosts.
+scd.reset()
+
+# The MCP2221 is known to not like the SCD30 reset hiccup.
+# See below for more information:
+# https://github.com/adafruit/Adafruit_CircuitPython_SCD30/issues/2
+# Can get around it by resetting via this hack.
+# pylint:disable=protected-access
+if hasattr(i2c, "_i2c"):
+    # we're using Blinka, check for MCP2221
+    if hasattr(i2c._i2c, "_mcp2221"):
+        # reset it
+        i2c._i2c._mcp2221._reset()
+
+while True:
+    # since the measurement interval is long (2+ seconds) we check for new data before reading
+    # the values, to ensure current readings.
+    if scd.data_available:
+        print("Data Available!")
+        print("CO2:", scd.CO2, "PPM")
+        print("Temperature:", scd.temperature, "degrees C")
+        print("Humidity:", scd.relative_humidity, "%%rH")
+        print("")
+        print("Waiting for new data...")
+        print("")
+
+    time.sleep(0.5)