A Balena project using a Raspberry Pi with a PiJuice and a DS18B20 1-wire temperature sensor to measure water temperature. The idea is to have a setup where the Pi wakes up at a given interval, measures the temperature and writes it to a MQTT message queue. Afterwards the Pi shuts down again. Internet connectivity is given via a USB dongle. Using the PiJuice and the solar panel which comes with it, we should be able to take measurements every few hours without being connected to power.
This is a sister project to balena-weather.
In order to use the Pijuice real time clock (RTC) and the one wire temperature sensor the following DT overlays must be set:
"i2c-rtc,ds3231,wakeup-source","w1-gpio,gpiopin=17"NOTE: This uses the non default GPIO pin 17 (opposed to 4).
| Variable | Description | Values |
|---|---|---|
| MQTT_BROKER | MQTT server name | localhost |
| MQTT_BROKER_PORT | MQTT web-socket port | 80 |
| SLEEP_INTERVAL | Time between measurements | 60 |
| START_SSHD | Whether to open SSH port | [0|1] |
| STAY_ALIVE | Whether to stay alive after measurement | [0|1] |
In order to test the code easily, the container uses a trick to allow using PyCharm locally and execute the code in the remote container.
For that the container needs to open an SSH port.
This can be achieved setting the device service variable START_SSHD=1.
This will start sshd and allow PyCharm to use the container as a remote execution environment.
NOTE: This is a development trick/hack. In a production environment the sshd config should be removed.