Changing the OLED display contrast at specific times

ESPHome
1

Hello, I made a temperature display using ESP8622+SH1106. Below, I’m including the code. Everything works fine, but the display is too bright at night, and I would like to reduce its contrast to 10%, while during the day I would like to set it to 50%. I’ve tried various methods but couldn’t get it to work. Does anyone know a way to do this? Is it even possible?

time:
  - platform: sntp
    id: time_sntp   

sensor:
  - platform: homeassistant
    id: temperatura_ogrod
    entity_id: sensor.sonoffch4pror2_temperatura_na_zewntrz
    internal: true

i2c:
  sda: GPIO04
  scl: GPIO05
  frequency: 400kHz
  scan: False

font:
  - file: 'BebasNeue-Regular.ttf'
    id: font1
    size: 40

  - file: 'BebasNeue-Regular.ttf'
    id: font2
    size: 89

display:
  - platform: ssd1306_i2c
    id: wyswietlacz_OLED
    model: "SH1106 128x64"
    address: 0x3C
    contrast: 10%
    update_interval: 30s
    lambda: |-
      
      if (id(temperatura_ogrod).has_state()) {
        float temp = id(temperatura_ogrod).state;
        int temp_integer = (int)temp;
        int temp_fraction = (int)round((temp - temp_integer) * 10);
        char temp_integer_str[4];  // To store the integer part.
        char temp_fraction_str[14]; // To store the fractional part and the degree symbol.
        snprintf(temp_integer_str, sizeof(temp_integer_str), "%d", temp_integer);
        snprintf(temp_fraction_str, sizeof(temp_fraction_str), ".%d°", abs(temp_fraction)); // Using the abs() function to remove the minus sign.

        // Character width in pixels for BebasNeue-Regular.ttf at size 89.
        int char_width = 24;

        // Calculate the width of the integer part.
        int width_integer = strlen(temp_integer_str) * char_width + 10;
        
        // Positions from which the integer and fractional parts begin.
        int start_x_integer = 0;
        int start_x_fraction = 0;

        // Conditions for different lengths of the integer part of the text.
        if (strlen(temp_integer_str) == 1) {
          // For single-digit positive temperatures.
          start_x_integer = 47;
          start_x_fraction = start_x_integer + width_integer;
        } else if (strlen(temp_integer_str) == 2) {
          // For single-digit negative temperatures and double-digit positive temperatures.
          // Special position for negative single-digit temperatures.
          if (temp_integer < 0) {
            start_x_integer = 20;
            start_x_fraction = start_x_integer + width_integer;
          } else {
          start_x_integer = 20;
          start_x_fraction = start_x_integer + width_integer + 12;
          }
        } else if (strlen(temp_integer_str) == 3) {
          // For double-digit negative temperatures.
          start_x_integer = -5;
          start_x_fraction = start_x_integer + width_integer + 12;
        }

        // Displaying temperatures in the correct positions.
        it.printf(start_x_integer, 90, id(font2), TextAlign::BOTTOM_LEFT, "%s", temp_integer_str); // Integer part
        it.printf(start_x_fraction, 60, id(font1), TextAlign::BASELINE_LEFT, "%s", temp_fraction_str); // Fractional part.
      } else {
        it.printf(64, 64, id(font2), TextAlign::BASELINE_CENTER, "--");
      }
2

This might help:

3

Thanks, it guided me a bit. The key turned out to be: .set_contrast(). I added an interval that checks the time every minute. If it is 10:00 PM or later and before 10:00 AM, the contrast is set to 1%. Rest of the day is set to 50%. It works as excepted.

interval:
  - interval: 1min
    then:
      - lambda: |-
          auto time = id(time_sntp).now();
          if (time.hour >= 22 || time.hour < 10) { 
            id(wyswietlacz_OLED).set_contrast(0.01);
          } else {
            id(wyswietlacz_OLED).set_contrast(0.5);
          }