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)