esphome/tests/components/key_collector/test.esp8266-ard.yaml

matrix_keypad:
  id: keypad
  rows:
    - pin: 12
    - pin: 13
  columns:
    - pin: 14
    - pin: 15
  keys: "1234"
  has_pulldowns: true

key_collector:
  - id: reader
    source_id: keypad
    min_length: 4
    max_length: 4
    on_progress:
      - logger.log:
          format: "input progress: '%s', started by '%c'"
          args: ['x.c_str()', "(start == 0 ? '~' : start)"]
    on_result:
      - logger.log:
          format: "input result: '%s', started by '%c', ended by '%c'"
          args: ['x.c_str()', "(start == 0 ? '~' : start)", "(end == 0 ? '~' : end)"]
    on_timeout:
      - logger.log:
          format: "input timeout: '%s', started by '%c'"
          args: ['x.c_str()', "(start == 0 ? '~' : start)"]