Get the value of a field in gravity forms

I need that when filling in a form, one field is automatically filled in with the value of another. I've been testing with:

add_filter( 'gform_field_value_titulo_proyecto', 
  function ( $valor ) {
    return gform_field_13_174;// modificando este valor
  }, 10, 1 );

, but I am unable to get enter the value of another field of the form.