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Frøy - ESP8266+BME Hygrometer

This repository contains the source code, schematics and everything else for my personal fancy homegrown hygrometer (sensor that reports temperature, humidity and pressure).

Features

  • push or pull mode
  • supports BME280, BME680 and BMP280 chips
  • programming via USB (only for indoor variant, others need a standalone USB->UART converter)
  • webserver with Prometheus compatible /metrics endpoint
  • reconfiguration via USB or WiFi (i.e. curl -XPOST -d'{"new":"config"}' http://device/)
  • OTA pull support (Frøy pulls new firmware from a specified location)
  • TLS support (single fingerprint only)
  • relatively easy to solder by hand (nothing smaller than an 0805 package)

Mode of Operation

Both indoor and outdoor versions can work in one of two modes:

  • Pull Mode ("server mode") -- in this mode, Frøy is constantly running and connected to your WiFi. It provides an HTTP server and expects you to fetch the data whenever you need it (for example via Prometheus).
  • Push Mode -- in this mode, Frøy will make a measurement, connect to WiFi, send out the data to a preconfigured URL and then go to sleep for a configurable amount of time. Rinse and repeat.

The advantage of the Pull Mode is that the interval can be centralled controlled (if you have multiple devices). It also makes it easier to trigger an OTA, as Frøy is constantly listening for requests.

The advantage of the Push Mode is that Frøy doesn't need any Firewall rules to be reachable and it saves power (critical for the Outdoor version). Also, indoor versions in Pull Mode would considerable heat up (an ESP8266 that is connected to WiFi can be 35-40°C) and skew the sensor readings. So even for indoor versions it is advisable to use Push Mode instead.

While Frøy is not reachable in Push Mode (it never starts a webserver and you'd be pretty luck to send a request to it the moment it wakes up and before it goes back to sleep), it is still possible to reconfigurable Frøy remotely by putting the new configuration in the response to Frøy's push request.

Flavors

Frøy currently comes in three flavors:

Frøy Outdoor

This is the original project. It runs using a CR123 battery, which lasts roughly 3-5 months when reporting data every 15 minutes.

The case can be bought on Amazon: https://www.amazon.de/gp/product/B072M2JKGW/ -- I am not aware of any alternative sources. In case the product disappears, I saved the schematics in docs/images/froy-outdoor-case-drawings.jpg.

Frøy Indoor

This variant is powered by USB and suitable for indoor use.

Froy ForMen

This variant is powered by mains voltage and is suitable for locations where changing the battery regularly is not desirable.

The case can be bought on Amazon, for example https://www.amazon.de/gp/product/B07B9KY9X4/ -- alternatively search for "Snowsound case" on your favorite search engine.

Frøy was named after the character in the NRK series "Norsemen".