ESPHome GPIO Touch Sensor as Capacitive Input for Waterlevel

ESPHome
6

Calibrate linear or polynomial filter should work to map reading to level percent. This would let calibration be adjustable via yaml config. Otherwise you could write a function to map reading to the percent and pass that to publish_state()

publish_state(-0.0022*reading*reading*reading + 0.2778*reading*reading - 11.889*reading + 193.33);

Below sample uses a lambda call that will get the raw value from the esp32 touch binary sensor and returns it in a template sensor (as an alternative to your custom component).

esphome:
  name: capacitive-level-test

esp32:
  board: esp32dev
  framework:
    type: arduino

# Enable Home Assistant API
api:

logger:
  baud_rate: 115200

ota:
  password: !secret esp_home_ota_pw

wifi:
  ssid: !secret wifi_ssid
  password: !secret wifi_password
  
# Sync time with Home Assistant.
time:
  - platform: homeassistant
    id: homeassistant_time

esp32_touch:
  setup_mode: false

binary_sensor:
  - platform: esp32_touch
    #name: "ESP32 Touch Pad GPIO27"
    pin: GPIO27
    threshold: 1000
    id: capacitive_level_hack

sensor:
  - platform: template
    name: "Water Level"
    icon: mdi:car-coolant-level
    update_interval: 1s
    lambda: |-
      return (float) id(capacitive_level_hack).get_value();
    filters:
      - calibrate_linear:
        - 20.0 -> 100.0
        - 2080.0 -> 0.1