Software to read out Sensirion SCD30 CO₂ Sensor values over I2C on Raspberry Pi.
This software is licenced under GPLv3 by UnravelTEC OG (https://unraveltec.com), 2018.
sudo raspi-config navigate to P5 I2C and select <Yes>.
- SCD30: RX/SDA -> Pi: I2C1 SDA (GPIO2)
- SCD30: TX/SCL -> Pi: I2C1 SCL (GPIO3)
- SCD30: VIN -> Pi: 3.3V/5.5V (use one of PWR pinouts)
- SCD30: GND -> Pi: GND (use one of GND pinouts)
You might need to run the following commands as root e.g. by typing sudo before running a specific command.
Install the following python-libraries:
aptitude install python-crcmod
As the SCD30 needs complex i2c-commands, the Linux standard i2c-dev doesn't work. A working alternative is pigpiod.
aptitude install pigpio python-pigpio
Atm, IPv6 doesn't work on Raspbian correctly with pigpiod, so:
sed -i "s|^ExecStart=.*|ExecStart=/usr/bin/pigpiod -l -n 127.0.0.1|" /lib/systemd/system/pigpiod.service
systemctl restart pigpiod
# Test (should return an int)
pigs hwver
Master needs to support Clock Stretching up to 150ms. The default in Raspbian is too low, we have to increase it:
To set it, download from here:
https://github.com/raspihats/raspihats/tree/master/clk_stretch
Compile:
gcc -o i2c1_set_clkt_tout i2c1_set_clkt_tout.c
gcc -o i2c1_get_clkt_tout i2c1_get_clkt_tout.c
execute (add to /etc/rc.local to run on every boot):
./i2c1_set_clkt_tout 20000 # for 200ms
Remember: Maximum I2C speed for SCD30 is 100kHz.
You might need to run the following as root e.g. by typing sudo before running the script.
python scd30.py
cp scd30.py /usr/local/bin
cp scd30-service.sh /usr/local/bin
cp scd30.service /etc/systemd/system/
systemctl enable scd30.service
systemctl start scd30.service
the service writes a file /run/scd30 (which resides in RAM) - it is meant to be read out by prometheus.
pressure value for pressure compensation is currently done via a constant (972mbar ~ altitude of 300m)