diff --git a/inc/protocol.h b/inc/protocol.h
--- a/inc/protocol.h
+++ b/inc/protocol.h
@@ -55,8 +55,9 @@ typedef enum {
     WATER_PH = 0x000E,
     CAN_ID = 0x0100,
     DATA_RATE = 0x0101,
-    GPIO = 0x0102,
-    LED_BRIGHTNESS = 0x0103,
+    LED_BRIGHTNESS = 0x0102,
+    INPUT = 0x0103,
+    OUTPUT = 0x0104,
 } protocol_data_key_t;
 
 void protocol_init(protocol_device_t device);