Hello people,
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?
As long as these requirements are met of course (as per the docs)…
In order to see data in history graph you need to use either widgets with “Frequency reading” interval (in that case your app should be open and running) or you can use Blynk.virtualWrite on hardware side. Every Blynk.virtualWrite command is stored on server automatically. In that case you don’t need application to be up and running.