This is a REST service written in python using fastapi that reads data from a Bosch BME280 sensor connected to a raspberry pi's I2C bus.
Bosch's BME280 sensor is a small, low cost, low power sensor that measures ambient temperature, pressure and relative humidity. Data is read via an I2C or SPI bus, both of which are provided by the Raspberry Pi 4.
I'm using the Raspberry Pi 4 to host an instance of homeassistant, an open source and (mostly) excellent community home automation solution. Up until recently (mid-2022, that is), the team provided support for a BME280 connected to the Pi's I2C bus, offering me a great, simple and low-cost solution to most of my measurement needs.
Sadly, since then, the team decided to not only drop support for anything GPIO, but also to remove all integrations using it entirely. At that point, I already had weather.py lying around from playing with the sensor before, and thus this project was born. At this point, I like to thank the kind developer who put their python code up for everyone to use in a blog article that I sadly can't seem to find anymore.
What problem do I solve doing it this way? Instead of just using ESPHome (which actually seems to be a wonderful project as far as I can tell!) as mostly everyone suggested, I decided to stitch together something in software so my smooth software developer brain wouldn't have to deal with hardware problems like powering an ESP32 or ESP8266 and having all that gross wiring dangling everywhere.
But how does that solve my problem? Great question! As long as the homeassistant team doesn't decide to remove the RESTful sensor integration, I can use it to query sensor data via HTTP from an API wrapping my wonderful weather.py, which hasn't changed much in about 3 years. What a burden to maintain, indeed! (I'm kidding here, big thanks to the kind developers of RPi.bme280!).
Currently, I'm building the image using docker on my Raspberry Pi. However, it should be possible to build it on any arm64 or using cross-architecture support. I haven't looked into that yet. Right now, running the following on an RPi4 with this repository checked out does the trick:
docker build -t sensor .As I am running homeassistant along with other software using docker compose, here is the relevant
part of my docker-compose.yml to properly run this image in a setup like mine:
version: "3"
services:
sensor:
image: sensor:latest
container_name: sensor
devices:
- /dev/i2c-1:/dev/i2c-1
privileged: true
restart: unless-stopped
...
This way, my homeassistant instance can reach the sensor data server at http://sensor/. How do I
make use of that? Easy! Just squeeze out some more YAML, you can do it! Here is the relevant excerpt
from the configuration.yml used by homeassistant.
sensor:
- platform: rest
name: ambient_sensor
resource: http://sensor/
json_attributes:
- temperature
- pressure
- humidity
icon: mdi:chip
- platform: template
sensors:
temperature:
value_template: "{{ state_attr('sensor.ambient_sensor', 'temperature') | round(1) }}"
device_class: temperature
unit_of_measurement: "°C"
pressure:
value_template: "{{ state_attr('sensor.ambient_sensor', 'pressure') | round(0) }}"
device_class: pressure
unit_of_measurement: "mbar"
humidity:
value_template: "{{ state_attr('sensor.ambient_sensor', 'humidity') | round(0) }}"
device_class: humidity
unit_of_measurement: "%"
outside_temperature:
value_template: "{{ state_attr('weather.home', 'temperature') | round(1) }}"
device_class: temperature
unit_of_measurement: "°C"
Because. Look, I'm not particularly happy about it either. At least, fastapi seems to be the way to go about it these days, and it works well for me.
Probably because I didn't care to look into it before.
I know, I know. It's gonna be alright :)