Wiimote/Extension Controllers/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 (0-63), 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.

Hardware

Wii Classic Controller circuit board, top surface

Wii Classic Controller circuit board, bottom surface

The classic controller uses several different hardware parts for its various inputs.

Input	Hardware	Circuit board surface and mounting
A	membrane switch	top
B	membrane switch	top
-	microswitch	top
Home	microswitch	top
+	microswitch	top
X	membrane switch	top
Y	membrane switch	top
Up	membrane switch	top
Down	membrane switch	top
Left	membrane switch	top
Right	membrane switch	top
Left joystick X	axial potentiometer, 30KΩ	daughterboard, through-hole
Left joystick Y	axial potentiometer, 30KΩ	daughterboard, through-hole
Right joystick X	axial potentiometer, 30KΩ linear	daughterboard, through-hole
Right joystick Y	axial potentiometer, 30KΩ linear	daughterboard, through-hole
L trigger range	slider potentiometer, 30KΩ linear	bottom, through-hole
R trigger range	slider potentiometer, 30KΩ linear	bottom, through-hole
L trigger bottom-out switch	membrane switch	daughterboard, through-hole
R trigger bottom-out switch	membrane switch	daughterboard, through-hole
ZL	SPST switch	bottom, through-hole
ZR	SPST switch	bottom, through-hole

The left and right trigger buttons are force-sensitive. As the trigger is pressed, a mechanism slides a 30KΩ linear potentiometer. However, the mechanism only uses about 1/4 of the full travel of the potentiometer. At the bottom of that travel, the mechanism actuates a switch. One might speculate that the bottom-out switch allows the controller to tolerate manufacturing differences between potentiometers without going through a calibration step. Regardless of the variation in the potentiometer, the trigger is considered fully pressed when the bottom-out switch closes.

It appears that all six of the potentiometers on the device: both triggers, both axes of each joystick, appear to be wired in parallel. All of the ends appear to be wired to the unit's power supply and ground, and the wiper (the electrical part that indicates the position of the slider) is probably are connected to analog-to-digital inputs on the microcontroller. Thus, one might speculate that the voltage that the microcontroller sees is between 3.3 and 0 volts. So it may be possible to repurpose these ranged inputs to measure other electrical signals in the same voltage range.

The through-hole switches should be easy to replace with soldered-in leads and moved to an off-board switch. Membrane switches should also be repurposable, but not as readily.