diff --git a/Makefile b/Makefile
index 7b9afa5..bd964f1 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,6 @@
 TARGET = 351Files

+# DEVICE ?= RG503
 # DEVICE ?= RG351P
 # DEVICE ?= RG351V
 # DEVICE ?= RGB10
diff --git a/src/def.h b/src/def.h
index 92d1a01..db4fec4 100644
--- a/src/def.h
+++ b/src/def.h
@@ -85,6 +85,22 @@
    #define KEYBOARD_MARGIN          8
    #define KEYBOARD_KEY_SPACING     4

+// Parameters for RG503
+#elif defined(DEVICE_RG503)
+   #define SCREEN_WIDTH             960
+   #define SCREEN_HEIGHT            544
+   #define HARDWARE_ACCELERATION    0
+   #define FULLSCREEN               1
+   #define FONT_NAME                "NotoSans-Regular.ttf"
+   #define FONT_NAME_MONO           "NotoSansMono-Regular.ttf"
+   #define FONT_SIZE                24
+   #define LINE_HEIGHT              36
+   #define ICON_SIZE                29
+   #define MARGIN_X                 12
+   #define KEYBOARD_MARGIN          10
+   #define KEYBOARD_KEY_SPACING     5
+   #define KEYBOARD_SYMBOL_SIZE     29
+
 // Paramaters for desktop PC
 #else
    #define SCREEN_WIDTH             640
@@ -124,7 +139,26 @@
 #define VIEWER_SCROLL_SPEED      20

 // Button events
-#if defined(DEVICE_RG351P)
+#if defined(DEVICE_RG503)
+   #define BUTTON_PRESSED_UP              event.type == SDL_JOYBUTTONDOWN && event.jbutton.button == 13
+   #define BUTTON_PRESSED_DOWN            event.type == SDL_JOYBUTTONDOWN && event.jbutton.button == 14
+   #define BUTTON_PRESSED_LEFT            event.type == SDL_JOYBUTTONDOWN && event.jbutton.button == 15
+   #define BUTTON_PRESSED_RIGHT           event.type == SDL_JOYBUTTONDOWN && event.jbutton.button == 16
+   #define BUTTON_PRESSED_PAGEUP          event.type == SDL_JOYBUTTONDOWN && (event.jbutton.button == 4 || event.jbutton.button == 6)
+   #define BUTTON_PRESSED_PAGEDOWN        event.type == SDL_JOYBUTTONDOWN && (event.jbutton.button == 5 || event.jbutton.button == 7)
+   #define BUTTON_PRESSED_VALIDATE        event.type == SDL_JOYBUTTONDOWN && event.jbutton.button == 1
+   #define BUTTON_PRESSED_BACK            event.type == SDL_JOYBUTTONDOWN && event.jbutton.button == 0
+   #define BUTTON_PRESSED_MENU_CONTEXT    event.type == SDL_JOYBUTTONDOWN && event.jbutton.button == 2
+   #define BUTTON_PRESSED_SELECT          event.type == SDL_JOYBUTTONDOWN && event.jbutton.button == 3
+   #define BUTTON_HELD_UP                 SDL_JoystickGetButton(g_joystick, 13)
+   #define BUTTON_HELD_DOWN               SDL_JoystickGetButton(g_joystick, 14)
+   #define BUTTON_HELD_LEFT               SDL_JoystickGetButton(g_joystick, 15)
+   #define BUTTON_HELD_RIGHT              SDL_JoystickGetButton(g_joystick, 16)
+   #define BUTTON_HELD_PAGEUP             SDL_JoystickGetButton(g_joystick, 4) || SDL_JoystickGetButton(g_joystick, 6)
+   #define BUTTON_HELD_PAGEDOWN           SDL_JoystickGetButton(g_joystick, 5) || SDL_JoystickGetButton(g_joystick, 7)
+   #define BUTTON_HELD_SELECT             SDL_JoystickGetButton(g_joystick, 3)
+   #define BUTTON_HELD_VALIDATE           SDL_JoystickGetButton(g_joystick, 1)
+#elif defined(DEVICE_RG351P)
    #define BUTTON_PRESSED_UP              event.type == SDL_JOYHATMOTION && event.jhat.value == SDL_HAT_UP
    #define BUTTON_PRESSED_DOWN            event.type == SDL_JOYHATMOTION && event.jhat.value == SDL_HAT_DOWN
    #define BUTTON_PRESSED_LEFT            event.type == SDL_JOYHATMOTION && event.jhat.value == SDL_HAT_LEFT