Testpads

The Nintendo Switch mainboard has a series of testpads on the front and back, presumably used in factory test, diagnostics, and early board bringup procedures.

Raw Logic captures

These are reference materials, taken from poking at I/O on various testpads. https://github.com/hedgeberg/Switch-Logic-Captures

Photos

Pinouts

Cluster A

Pad #	Name	Type	Levels	Continuity	Frequency	Comment
1	Batt GND?
2	Battery pulse?	Pulse train	0-3.3V	L-5?
3	Battery Vdd
4	??	Square wave	0-3.3V		329kHz? (undersampled?)	Square wave when screen on, but looks like vias to Speaker R
5	??	Square wave	0-3.3V		329kHz? (undersampled?)	Square wave when screen on, but looks like vias to Speaker R
6	Weak GND?
7	SDA	I2C	0-1.8V
8	SCL	I2C	0-1.8V
9	USB-PWR-WAVE?	Square wave	0-3.3V	K-4, K-5?	~11 Hz
10	USB-PWR-WAVE?	Square wave	0-3.3V	K-4, K-5?	~11 Hz

Cluster C

Pad #	Name	Type	Levels	Continuity	Frequency	Comment
1	??		0-1.8V		No clue. This is definitely important, we just have no idea how. May need to interface with dock for comms.
2	UART-A RX		0-1.8V
3	UART-A TX		0-1.8V
4	??		0-1.8V
5	??		0-1.8V
6	??		0-1.8V
7	??		0-1.8V
8	??		0-1.8V
9	??		0-1.8V
10	??		0-1.8V
11	??		0-1.8V

Cluster E

DON'T FUCK WITH CLUSTER E.

Pad #	Name	Type	Levels	Continuity	Frequency	Comment
10	Reset

Cluster I

Pad #	Name	Type	Levels	Continuity	Frequency	Comment
1	GND
2	Screen_on	On/Off	0-1.8V			Screen power state, active high
3		UART	0-1.8V		1.5MBaud?	needs testing with screen plugged in. Sends string ‘Nintendo Switch’ + some stuff. long string of 00
4		UART	0-1.8V		1.5MBaud?	needs testing with screen plugged in. some kind of call/response for pad I-3
5		Flow control	0-1.8V			Flow control for pad I-4?
6			0-1.8V			Needs testing with chip/touch screen interface board plugged in

Cluster J

Pad #	Name	Type	Levels	Continuity	Frequency	Comment
1	?	Edge	0-1.8V			Turns on around same time as pad J-3
2	GND
3	?	Edge	0-1.8V			Turns on around same time as pad J-1, slightly after
4	Power button	Pushbutton	4V-0V			Active low
5	?	Constant?	0V	Ground?-NT
6	?	Edge	0-1.8V			Turns on with pad J-6, ~1s after J-1/J-3
7	?	Edge	0-1.8V			Turns on with pad J-5, ~1s after J-1/J-3
8	?	Edge?	0-1.8V			Turns on ~1s after J-6/J-7, turns off at unknown point

Cluster K

Pad #	Name	Type	Levels	Continuity	Frequency	Comment
1	GND
2	Unknown	??	3.3V-0V	None known	N/A?	Falls around same time pad K-7 falls, but immediately. No data observed as of yet.
3	Unknown
4	USB-PWR-WAVE?	Square wave	0V-3.3V	A-9, A-10?	~11 Hz
5	USB-PWR-WAVE?	Square wave	0V-3.3V	A-9, A-10?	~11 Hz	Appears to mirror K4. Duty cycle 66.67%. Low on screen lock. Off until first interaction.
6	USB-C V+	Supply power
7	Unknown	Power supply?	~3V-0V	None known	N/A	0 when usb-c not plugged in, falls slowly on first interaction if USB-C plugged in. Power draw related?

Cluster L

TODO: Update diagram

Pad #	Name	Type	Levels	Continuity	Frequency	Comment
1	Li-Ion Batt Vdd Mirror	Power Supply	Std. Li-Ion
2	GND
3	Li-Ion Batt Vdd	Battery Input	Std. Li-Ion
4	Mirrored Ground?					Holds steady @ 0, looks like a decoupled isolated ground
5	Battery pulse?				<1 Hz	Duty cycle ~0%