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	Speaker R +	Square wave	0-3.3V			Speaker Right +
5	Speaker R -	Square wave	0-3.3V			Speaker Right -
6	Weak GND?
7	SDA	I2C	0-1.8V			I2C Port 0
8	SCL	I2C	0-1.8V			I2C Port 0
9	USB-PWR-WAVE?	Square wave	0-3.3V	K-4, K-5?	~11 Hz	USB CC2
10	USB-PWR-WAVE?	Square wave	0-3.3V	K-4, K-5?	~11 Hz	USB CC1

Cluster B

Pad #	Name	Type	Levels	Continuity	Frequency	Comment
1		DBVDD				from ALC5639 pin 43
2	D+	USB-C				Cluster B - 3
3	D-	USB-C				Cluster B - 2
4	+3.3V	XRST				from M92T36 pin 4
5	+3.3V	VSVR				from M92T36 pin 6
5(b)	VUSB	VB				from M92T36 pin 9
6	GND

Cluster C

The JTAG pins are multiplexed between NV_JTAG and ARM_JTAG by the TRST pin:

• NV_JTAG contains a single TAP (ID 0x221173D7) for boundary scan board verification.
• ARM_JTAG contains two debugging TAPs for CoreSight (ID 0x5BA00477) and BPMP (ID 0x4F1F0F0F).

Note: NV_JTAG and ARM_JTAG are locked out by FUSE_ARM_JTAG_DIS on production devices.

Pad #	Name	Type	Levels	Continuity	Frequency	Comment
1	JTAG_TDI		0-1.8V
2	UART1_RX		0-1.8V			UART-A RX
3	UART1_TX		0-1.8V			UART-A TX
4	JTAG_TCK		0-1.8V
5	JTAG_RTCK		0-1.8V			Unused for NV_JTAG
6	UART1_RTS		0-1.8V			UART-A RTS Flow control
7	JTAG_TDO		0-1.8V
8	UART1_CTS		0-1.8V			UART-A CTS Flow control
9	JTAG_TMS		0-1.8V
10	JTAG_TRST_N		0-1.8V			Not a TAP reset; Multiplexes between NV_JTAG (HI) and ARM_JTAG (LO)
11	+1.8V		0-1.8V

Cluster D

Pad #	Name	Type	Levels	Continuity	Frequency	Comment
1	GND
4	Seaker L +					Speaker Left +
5	Seaker L -					Speaker Left -

Cluster E

Pad #	Name	Type	Levels	Continuity	Frequency	Comment
1	Vol (-)					Button Vol (-)
10	Reset
11	Power Button	Pushbutton	4V-0V			Active low

Cluster G

Pad #	Name	Type	Levels	Continuity	Frequency	Comment
1	SD card detect
2	GND
3	Rail	DC	0v8			GPU Buck
4	Vol(+)					Button Vol (+)
5	Li-Ion Batt Vdd Mirror					Power Supply
9	BUTTON_HOME					RCM strap

Cluster H

Pad #	Name	Type	Levels	Continuity	Frequency	Comment
1
2
3
4	Screen_on	On/Off	0-1.8v	I-2		Screen power state, active high
5		Flow control	0-1.8V	I-5	Flow control for pad I-4?
6
7		UART	0-1.8V	I-4	1.5MBaud?
8		UART	0-1.8V	I-3	1.5MBaud?
9
10			5V	H-12		Power for JoyCon charge circuit and fan
11						Goes to a small ceramic cap near WiFi/BT IC?
12				H-10		On the same trace

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?	Communication CPU -> Bluetooth using HCI
4		UART	0-1.8V		1.5MBaud?	Communication Bluetooth -> CPU using HCI
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	D-	USB-C				Cluster B - 3
3	D+	USB-C				Cluster B - 2
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				support fast charger : "normal mode = 5V+" "Fast changer = 12V+"
7	BQ24193 VBUS + M92T36 VEX	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%
6	GND