My concept is to make a simple MicroPython script on the M5StickC. I have no experience with humidity measurement. I do not know how often is enough to measure. That’s why I will have a variable (divisor) in the script which is set by the Node-RED interface. Each measurement should be saved with time stamp. The M5StickC shall not connect to the Wifi for a time check. It should get once a day one time stamp from the Node-RED server and calculate the rest of the time stamps by adding 24h/divisor. Once a day the data should be pushed to the Node-RED server. The server should display the data on a dashboard (in a browser) and should save the data in a csv file on the BPI Berry. My preferred protocol for this kind of tasks is CoAP.

The following figure shows the workflow of the whole system.