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 B

Pad # Name Type Levels Continuity Frequency Comment
2 D+ USB-C Cluster B - 3
3 D- USB-C Cluster B - 2


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 D

Pad # Name Type Levels Continuity Frequency Comment
4 Wire Red Speaker left
5 Wire Black Speaker left

Cluster E

Pad # Name Type Levels Continuity Frequency Comment
10 Reset

Cluster G

Pad # Name Type Levels Continuity Frequency Comment
9 RCM_EN RCM strap to connect GND

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?
4 UART 0-1.8V 1.5MBaud?
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
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%
6 GND