Proxy Luftdaten from your Feinstaubsensor to OpenWeatherMap

The main part of data.php is taken from the original repo https://github.com/opendata-stuttgart/madavi-api, but before handling the data the connection is closed to free resources on your Airrohr.

• Register at OpenWeatherMap and receive an api key.
• Find out geo data of your Feinstaubsensor.
• Save these params to config.inc.php.
• Call php command.php install to get your station id and store it as well.
• Make data.php accessible from your Feinstaubsensor and configure the sensor to send data to it.