clean up example output

slow down i2c to 1khz (works on ft232h now)
add inter-command delays (5ms)

Author: ladyada

adafruit_scd30.py

@@ -28,7 +28,7 @@
 """
 
 # imports
-from time import sleep
+import time
 from struct import unpack_from, unpack
 import adafruit_bus_device.i2c_device as i2c_device
 from micropython import const
@@ -107,7 +107,7 @@ 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(0.1)  # not mentioned by datasheet, but required to avoid IO error
+        time.sleep(0.1)  # not mentioned by datasheet, but required to avoid IO error
 
     @property
     def measurement_interval(self):
@@ -147,7 +147,7 @@ def self_calibration_enabled(self):
     def self_calibration_enabled(self, enabled):
         self._send_command(_CMD_AUTOMATIC_SELF_CALIBRATION, enabled)
         if enabled:
-            sleep(0.01)
+            time.sleep(0.01)
 
     @property
     def data_available(self):
@@ -278,13 +278,15 @@ def _send_command(self, command, arguments=None):
 
         with self.i2c_device as i2c:
             i2c.write(self._buffer, end=end_byte)
+        time.sleep(0.05) # 3ms min delay
 
     def _read_register(self, reg_addr):
         self._buffer[0] = reg_addr >> 8
         self._buffer[1] = reg_addr & 0xFF
         with self.i2c_device as i2c:
             i2c.write(self._buffer, end=2)
         # separate readinto because the SCD30 wants an i2c stop before the read (non-repeated start)
+        time.sleep(0.005)  # min 3 ms delay
         with self.i2c_device as i2c:
             i2c.readinto(self._buffer, end=2)
         return unpack_from(">H", self._buffer)[0]

examples/scd30_simpletest.py

@@ -4,18 +4,22 @@
 import time
 import board
 import adafruit_scd30
+import busio
 
-i2c = board.I2C()  # uses board.SCL and board.SDA
+# SCD-30 has tempremental I2C with clock stretching, and delays
+# It's best to start using I2C clock 1000 Hz and then you can increase it
+# until the sensor stops responding (NAK fails, etc)
+i2c = busio.I2C(board.SCL, board.SDA, frequency=1000)
 scd = adafruit_scd30.SCD30(i2c)
 
 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("CO2: %d PPM" % scd.CO2)
+        print("Temperature: %0.2f degrees C" % scd.temperature)
+        print("Humidity: %0.2f %% rH" % scd.relative_humidity)
         print("")
         print("Waiting for new data...")
         print("")