It shouldn't be too hard to make this library platform-agnostic, as the changes to make it CircuitPython-compatible were pretty minimal. I haven't tried using Blinka, which might have been the "right" way to deploy this in my project anyway. I'm not sure how Blinka's supposed to work in situations like this. Maybe it's relevant.
Sensirion SCD30 is a CO², Humidity and Temperature sensor on a module. This is a I2C driver written in Python 3 for MicroPython.
- Sensirion SCD30 Sensor Module
- MicroPython board with I2C interface
Wire the I2C bus to the I2C bus on your MicroPython board. This is an example using the Pyboard D:
| Pyboard | SCD30 |
|---|---|
| X15 (3V3) | VDD |
| X14 (GND) | GND |
| X9 | TX/SCL |
| X10 | RX/SDA |
This example reads the measurements in a continous loop:
import time
from machine import I2C, Pin
from scd30 import SCD30
i2cbus = I2C(1)
scd30 = SCD30(i2c, 0x61)
while True:
# Wait for sensor data to be ready to read (by default every 2 seconds)
while scd30.get_status_ready() != 1:
time.sleep_ms(200)
scd30.read_measurement()CircuitPython Example:
import time
import board
from scd30 import SCD30
i2c = board.I2C()
scd30 = SCD30(i2c, 0x61)
while 1:
while scd30.get_status_ready() != 1:
time.sleep(0.200)
print("getting measurement")
try:
co2, temp, relh = scd30.read_measurement()
except CRCException:
pass
print(co2)
print(temp)
print(relh)Note that the CO² sensor needs some time to stabilize. Therefor the sensor should be kept powered to achieve a reasonable measurement interval (e.g. <5 minutes). To save power the sensors measurement inverval can be tweaked. See also the Low Power Mode for SCD30 application note.
The CO² sensor has two modes of calibration: FRC (Forced Recalibration) or ASC (Automatic Self-Calibration). This only describes the former.
Essentially the sensor is already calibrated at factory. However, when setting a new measurement interval recalibration might be necessary. The process is to bring the sensor into a controlled environment (e.g. outside) and set the known value at that environment (e.g. 400ppm). From what I understand ASC does essentially the same, just assumes that the lowest values over a certain periode are "outside values"...
Also note that the temperature sensor suffers from heating effects on the PCB. When the sensor operates in 2 second interval the heating is about 3°C. I usually run the sensor at 30 seconds interval and observed a heating of 2°C. The offset is subtracted from the measured temperature! To set a new offset, take the old offset into account!
This project is licensed under the MIT License - see the LICENSE file for details