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Using the StemmaQT/Qwicc connector

The Pioreactor HAT comes with a connector for the StemmaQT / Qwiic connector that can be used to attach additional hardware for your Pioreactor. See image below:


What is StemmaQT / Qwiic? It's simply a standardized physical connector, the JST SH, with electronic connections to 3.3V, GND and I²C. Many other hardware design companies, like Adafruit and SparkFun, implement StemmaQT / Qwiic on their boards, which expands the StemmaQT / Qwiic ecosystem.


Suppose you are placing your Pioreactor in a CO₂ incubator, and want to record the CO₂ concentration of the incubator. The incubator does monitor the CO₂ concentration, but generally this isn't accessible to other tools. What you can do is purchase an external CO₂ sensor with StemmaQT / Qwiic connectors, like the SCD-40, and attach it to your Pioreactor. The Pioreactor can now read from the CO₂ sensor, and build logging, event-loops, plotting, etc. around the measurements.

To read from the sensor, a plugin may be available for it, or you can write a simple Python script like so:


To run the script, you'll first need to install the Python library: sudo pip3 install adafruit-circuitpython-scd4x

import sleep
import board
import adafruit_scd4x

from pioreactor.pubsub import publish
from pioreactor.whoami import get_unit_name, get_latest_experiment_name

i2c = board.I2C()
scd4x = adafruit_scd4x.SCD4X(i2c)

exp = get_latest_experiment_name()
unit = get_unit_name()


while True:
if scd4x.data_ready:

print("CO2: %d ppm" % scd4x.CO2)
publish(f"pioreactor/{unit}/{exp}/scd4x/co2", scd4x.CO2, retain=True)

print("Temperature: %0.1f *C" % scd4x.temperature)
publish(f"pioreactor/{unit}/{exp}/scd4x/temperature", scd4x.temperature, retain=True)

print("Humidity: %0.1f %%" % scd4x.relative_humidity)
publish(f"pioreactor/{unit}/{exp}/scd4x/relative_humidity", scd4x.relative_humidity, retain=True)


Running this on your Pioreactor will publish the data to MQTT, and thus be available to any other bioreactor job.

You could also turn this into a background job to make it even easier to use!