fix sx1509 use of pullup and pulldown (#3689)

Co-authored-by: Samuel Sieb <samuel@sieb.net>

esphome/components/sx1509/__init__.py

@@ -9,6 +9,7 @@ from esphome.const import (
     CONF_MODE,
     CONF_INVERTED,
     CONF_OUTPUT,
+    CONF_PULLDOWN,
     CONF_PULLUP,
 )
 
@@ -74,6 +75,10 @@ def validate_mode(value):
         raise cv.Invalid("Mode must be either input or output")
     if value[CONF_PULLUP] and not value[CONF_INPUT]:
         raise cv.Invalid("Pullup only available with input")
+    if value[CONF_PULLDOWN] and not value[CONF_INPUT]:
+        raise cv.Invalid("Pulldown only available with input")
+    if value[CONF_PULLUP] and value[CONF_PULLDOWN]:
+        raise cv.Invalid("Can only have one of pullup or pulldown")
     return value
 
 
@@ -87,6 +92,7 @@ SX1509_PIN_SCHEMA = cv.All(
             {
                 cv.Optional(CONF_INPUT, default=False): cv.boolean,
                 cv.Optional(CONF_PULLUP, default=False): cv.boolean,
+                cv.Optional(CONF_PULLDOWN, default=False): cv.boolean,
                 cv.Optional(CONF_OUTPUT, default=False): cv.boolean,
             },
             validate_mode,