Merge pull request #7 from KeithTheEE/add_one_shot_co2

Add one shot co2 measurement

adafruit_scd4x.py

@@ -59,6 +59,8 @@
 _SCD4X_PERSISTSETTINGS = const(0x3615)
 _SCD4X_GETASCE = const(0x2313)
 _SCD4X_SETASCE = const(0x2416)
+_SCD4X_MEASURESINGLESHOT = const(0x219D)
+_SCD4X_MEASURESINGLESHOTRHTONLY = const(0x2196)
 
 
 class SCD4X:
@@ -147,6 +149,16 @@ def relative_humidity(self) -> float:
             self._read_data()
         return self._relative_humidity
 
+    def measure_single_shot(self) -> None:
+        """On-demand measurement of CO2 concentration, relative humidity, and
+        temperature for SCD41 only"""
+        self._send_command(_SCD4X_MEASURESINGLESHOT, cmd_delay=5)
+
+    def measure_single_shot_rht_only(self) -> None:
+        """On-demand measurement of relative humidity and temperature for
+        SCD41 only"""
+        self._send_command(_SCD4X_MEASURESINGLESHOTRHTONLY, cmd_delay=0.05)
+
     def reinit(self) -> None:
         """Reinitializes the sensor by reloading user settings from EEPROM."""
         self.stop_periodic_measurement()

examples/scd41_single_shot_example.py

@@ -0,0 +1,43 @@
+# SPDX-FileCopyrightText: 2021 by Keith Murray, written for Adafruit Industries
+#
+# SPDX-License-Identifier: Unlicense
+import time
+import board
+import adafruit_scd4x
+
+i2c = board.I2C()
+scd4x = adafruit_scd4x.SCD4X(i2c)
+print("Serial number:", [hex(i) for i in scd4x.serial_number])
+
+print("Waiting for single shot CO2 measurement from SCD41....")
+scd4x.measure_single_shot()
+
+sample_counter = 0
+while sample_counter < 3:
+    if scd4x.data_ready:
+        print("CO2: %d ppm" % scd4x.CO2)
+        print("Temperature: %0.1f *C" % scd4x.temperature)
+        print("Humidity: %0.1f %%" % scd4x.relative_humidity)
+        print()
+        scd4x.measure_single_shot()
+        sample_counter += 1
+    else:
+        print("Waiting...")
+    time.sleep(1)
+
+
+print("Waiting for single shot Humidity and Temperature measurement from SCD41....")
+scd4x.measure_single_shot_rht_only()
+
+sample_counter = 0
+while sample_counter < 3:
+    if scd4x.data_ready:
+        print("CO2: %d ppm" % scd4x.CO2)  # Should be 0 ppm
+        print("Temperature: %0.1f *C" % scd4x.temperature)
+        print("Humidity: %0.1f %%" % scd4x.relative_humidity)
+        print()
+        scd4x.measure_single_shot_rht_only()
+        sample_counter += 1
+    else:
+        print("Waiting...")
+    time.sleep(1)