diff --git a/mappings.c b/mappings.c
new file mode 100644
index 0000000..ec88408
--- /dev/null
+++ b/mappings.c
@@ -0,0 +1,80 @@
+#include "mappings.h"
+#include "gamepads.h"
+#include "usbpad.h"
+
+/* Default N64 and Gamecube mappings meant to work together
+ * i.e. Controllers should be mostly interchangeable
+ *
+ *  - Main buttons first
+ *  - Common buttons at the same place
+ *  - Similar layout for GC Y/X and N64 C-Left and C-Down
+ */
+
+static struct mapping map_gc_default[] = {
+	{ GC_BTN_A,		USB_BTN(0) },
+	{ GC_BTN_B,		USB_BTN(1) },
+	{ GC_BTN_Z,		USB_BTN(2) },
+	{ GC_BTN_START,	USB_BTN(3) },
+
+	{ GC_BTN_L,		USB_BTN(4) },
+	{ GC_BTN_R,		USB_BTN(5) },
+
+	{ GC_BTN_Y,		USB_BTN(8) }, // N64 C-Left
+	{ GC_BTN_X,		USB_BTN(7) }, // N64 C-Down
+
+	{ GC_BTN_DPAD_UP,		USB_BTN(10) },
+	{ GC_BTN_DPAD_DOWN,		USB_BTN(11) },
+	{ GC_BTN_DPAD_LEFT,		USB_BTN(12) },
+	{ GC_BTN_DPAD_RIGHT,	USB_BTN(13) },
+
+	{	} /* terminator */
+};
+
+static struct mapping map_n64_default[] = {
+	{ N64_BTN_A,			USB_BTN(0) },
+	{ N64_BTN_B,			USB_BTN(1) },
+	{ N64_BTN_Z,			USB_BTN(2) },
+	{ N64_BTN_START,		USB_BTN(3) },
+
+	{ N64_BTN_L,			USB_BTN(4) },
+	{ N64_BTN_R,			USB_BTN(5) },
+	{ N64_BTN_C_UP,			USB_BTN(6) },
+	{ N64_BTN_C_DOWN,		USB_BTN(7) }, // GC X
+
+	{ N64_BTN_C_LEFT,		USB_BTN(8) }, // GC_Y
+	{ N64_BTN_C_RIGHT,		USB_BTN(9) },
+
+	{ N64_BTN_DPAD_UP,		USB_BTN(10) },
+	{ N64_BTN_DPAD_DOWN,	USB_BTN(11) },
+	{ N64_BTN_DPAD_LEFT,	USB_BTN(12) },
+	{ N64_BTN_DPAD_RIGHT,	USB_BTN(13) },
+
+	{	} /* terminator */
+};
+
+static uint16_t domap(const struct mapping *map, uint16_t input)
+{
+	const struct mapping *cur = map;
+	uint16_t out = 0;
+
+	while (cur->ctl_btn && cur->usb_btn) {
+		if (input & cur->ctl_btn) {
+			out |= cur->usb_btn;
+		}
+		cur++;
+	}
+
+	return out;
+}
+
+uint16_t mappings_do(uint8_t mapping_id, uint16_t input)
+{
+	switch(mapping_id) {
+		case MAPPING_GAMECUBE_DEFAULT:
+			return domap(map_gc_default, input);
+		case MAPPING_N64_DEFAULT:
+			return domap(map_n64_default, input);
+	}
+
+	return 0;
+}
diff --git a/mappings.h b/mappings.h
new file mode 100644
index 0000000..ffa5d27
--- /dev/null
+++ b/mappings.h
@@ -0,0 +1,16 @@
+#ifndef _mappings_h__
+#define _mappings_h__
+
+#include <stdint.h>
+
+struct mapping {
+	uint16_t ctl_btn;
+	uint16_t usb_btn;
+};
+
+#define MAPPING_GAMECUBE_DEFAULT	0x00
+#define MAPPING_N64_DEFAULT			0x10
+
+uint16_t mappings_do(uint8_t mapping_id, uint16_t input);
+
+#endif // _mappings_h__
diff --git a/usbpad.h b/usbpad.h
index 3dbd361..ceaafd2 100644
--- a/usbpad.h
+++ b/usbpad.h
@@ -5,4 +5,7 @@ void usbpad_init(void);
 int usbpad_getReportSize(void);
 void usbpad_buildReport(const gamepad_data *pad_data, unsigned char *dstbuf);
 
+// For mappings. ID starts at 0.
+#define USB_BTN(id)	(0x0001 << (id))
+
 #endif // USBPAD_H__