Picool

A Raspberry Pi Zero controller for a refrigerator compressor. Also includes configuration for Telegraf to send data to Azure Monitor Metrics (which can be displayed with Grafana or Azure Monitor Workbooks).

Setup Pi Zero W Hardware

Wire all DS18B20 temperature sensors with DAT line on GPIO4.
Wire refrigerator relay VCC to GPIO17.

Setup OS

Install Raspberry Pi OS Lite to SD Card.
In /boot:
- Add empty ssh file.
- Add wpa_supplicant.conf with wifi SSID and PSK.
- Add dtoverlay=w1-gpio to config.txt.
Boot Pi and SSH in with default user pi password raspberry.
Change password and add authorized ssh key.

Setup Picool

Install Telgraf
- Add a resource_id to attach metrics in telegraf.conf copy it to /etc/telegraf.
- Fill in azuremonitor.env and copy it to /etc/telegraf.
  - The service principal needs "Monitoring Metrics Publisher" role on the resource in resource_id above.
  - Run chmod 600 azuremonitor.env.
- Copy 10-azuremonitor.conf into new directory /etc/systemd/system/telegraf.service.d.
- Run sudo systemctl enable telegraf, sudo systemctl start telegraf.
Install Picool
- Copy picool binary and influx_temps.sh into new directory /opt/picool and chmod 755 them.
- Fill in picool.env and copy it into /etc.
- Copy picool.service into /etc/systemd/system.
- Run sudo systemctl daemon-reload, sudo systemctl enable picool, sudo systemctl start picool.

Building for Raspberry Pi Zero

sudo apt install gcc-arm-linux-gnueabi
rustup target add arm-unknown-linux-gnueabi
cargo build --target arm-unknown-linux-gnueabi --release

Running

Assumes a temperature sensor and a relay for the compressor power is connected.

# picool <PATH TO TEMPERATURE FILE>                          <RELAY CONTROL GPIO PIN>
./picool "/sys/bus/w1/devices/28-00112233445566/temperature" 17

Demo Mode

Run cargo run --features demo-mode. This does not do any actual I/O and simulates the sensor.