History chart or graph for hardware display in ESPHome

ESPHome
,
6

there is actually a way to store historic values in ESPHome directly:

  1. Create a globals array
  2. In the sensor statement, update that array with an on_value statement
  3. Use the array values to print historic values.

Please be aware that arrays in ESPHome are barely documented… :nerd_face:

Here are some code sniplets that worked for me:

globals array

globals:
   - id: myhistory
     type: float[10]
     restore_value: no
     initial_value: "{'0','1','2','3','4','5','6','7','8','9'}"

sensor statement filling historic values on_value updates

sensor:
  - platform: homeassistant
    id: mysensor
    entity_id: sensor.whatever_sensor_you_have
    internal: true
    on_value:
      then:
        - lambda: |-
            for (int i = 9; i > 0; i--) {
              id(myhistory)[i] = id(myhistory)[i-1];
              }
            id(myhistory)[0] = id(mysensor).state;

This worked well to show some historic values on an M5 stack.

I will try some custom c++ code for some minigraphs next.