I am using blynk for a communication between my MEGA + ESP8266 + sensor, and I have some question about using it.
I want it in the blynk application (already created with a button + sensor reading) to see a history of the sensor values. I have read that the necessary widget would be History Graph, but I am not clear on how this works.
Is it necessary for History Graph to save the data (txt, or csv …) in an SD in order to read it, or save it in the CLOUD SERVER?
but I am not clear its use, could you put an example of it ?? (I’m going to pay for more energy but before I would like to know how exactly it works)