Wiimote/Extension Controllers

The Wiimote includes a 6-pin expansion port that allows external peripherals to be connected to it. Communications are bidirectional synchronous serial (the protocol is unknown), and the devices provide a virtual register block of length 0x100 that is mapped at 0xa40000 in the Wiimote's address space. Communications are encrypted, as detailed in Wiimote#Extension Controllers. Nintendo has currently released two extensions, the Nunchuk and the Classic Controller.

Peripheral Protocol is 400kHz "fast" I2C, with slave address 0x52. It should be possible to make homebrew peripherals; see the Tenkey project (japanese) or the Twiidler project

Nunchuk

The Nunchuk is identified by the 16-bit constant 0x0000 (0xFEFE encrypted) at register address 0xa400fe. It provides three-axis acceleration data, two digital buttons, and an X-Y analog stick.

Data Format

The Nunchuk reports its information as 6 bytes of data, readable at 0xa40008 and streamable using Data Reporting Modes that include Extension bytes (unused bytes are filled with 0x00). The data is packed into the six bytes as follows (after decryption):

	Bit
Byte	7	6	5	4	3	2	1	0
0	SX<7:0>
1	SY<7:0>
2	AX<7:0>
3	AY<7:0>
4	AZ<7:0>
5	Unknown						BC	BZ

SX,SY are the Analog Stick X and Y positions, while AX, AY, and AZ are the accelerometer data (in the same format as described in Wiimote#Accelerometer). BC and BZ are the state of the C and Z buttons (0=pressed).

Nintendo games calibrate the center position of the Analog Stick upon power-up or insertion of the Nunchuk.

Classic Controller

The Classic Controller is identified by the 16-bit constant 0x0101 (0xFDFD encrypted) at register address 0xa400fe. It provides 15 buttons, two of which are analog triggers and provide both "clicked" status and a distance pressed measurement, and two X-Y analog sticks.

Data Format

The Classic Controller reports its information as 6 bytes of data, readable at 0xa40008 and streamable using Data Reporting Modes that include Extension bytes (unused bytes are filled with 0x00). The data is packed into the six bytes as follows (after decryption):

	Bit
Byte	7	6	5	4	3	2	1	0
0	RX<4:3>		LX<5:0>
1	RX<2:1>		LY<5:0>
2	RX<0>	LT<4:3>		RY<4:0>
3	LT<2:0>			RT<4:0>
4	BDR	BDD	BLT	B-	BH	B+	BRT	1
5	BZL	BB	BY	BA	BX	BZR	BDL	BDU

LX,LY are the left Analog Stick X and Y (0-61), RX and RY are the right Analog Stick X and Y (0-31), and LT and RT are the Left and Right Triggers (0-31). The left Analog Stick has twice the precision of the other analog values.

BD{L,R,U,D} are the D-Pad direction buttons. B{ZR,ZL,A,B,X,Y,+,H,-} are the discrete buttons. B{LT,RT} are the digital button click of LT and RT. All buttons are 0 when pressed.

Nintendo games calibrate the center position of the Analog Sticks upon power-up or insertion of the Classic Controller.