Registers #

Old3DS	Name	Address	Width	Used by
Yes	I2C1_DATA	0x10161000	1	I2C bus 1 devices
Yes	I2C1_CNT	0x10161001	1	I2C bus 1 devices
Yes	I2C1_CNTEX	0x10161002	2	I2C bus 1 devices
Yes	I2C1_SCL	0x10161004	2	I2C bus 1 devices
Yes	I2C2_DATA	0x10144000	1	I2C bus 2 devices
Yes	I2C2_CNT	0x10144001	1	I2C bus 2 devices
Yes	I2C2_CNTEX	0x10144002	2	I2C bus 2 devices
Yes	I2C2_SCL	0x10144004	2	I2C bus 2 devices
Yes	I2C3_DATA	0x10148000	1	I2C bus 3 devices
Yes	I2C3_CNT	0x10148001	1	I2C bus 3 devices
Yes	I2C3_CNTEX	0x10148002	2	I2C bus 3 devices
Yes	I2C3_SCL	0x10148004	2	I2C bus 3 devices

I2C_CNT #

BIT	DESCRIPTION
0	Stop (0=No, 1=Stop/last byte)
1	Start (0=No, 1=Start/first byte)
2	Pause (0=Transfer Data, 1=Pause after Error, used with/after Stop)
4	Ack Flag (0=Error, 1=Okay) (For DataRead: W, for DataWrite: R)
5	Data Direction (0=Write, 1=Read)
6	Interrupt Enable (0=Disable, 1=Enable)
7	Start/busy (0=Ready, 1=Start/busy)

I2C_CNTEX #

BIT	DESCRIPTION
0-1	? Set to 2 normally.

I2C_SCL #

BIT	DESCRIPTION
0-5	?
8-12	? Set to 5 normally.

I2C Devices #

Device id	Device bus id	Device Write Address	Accessible via I2C service	Device description
0	1	0x4a	“i2c::MCU”	Power management?(same device addr as the DSi power-management)
1	1	0x7a	“i2c::CAM”	Camera0?(same dev-addr as DSi cam0)
2	1	0x78	“i2c::CAM”	Camera1?(same dev-addr as DSi cam1)
3	2	0x4a	“i2c::MCU”	MCU
4	2	0x78	“i2c::CAM”	?
5	2	0x2c	“i2c::LCD”	?
6	2	0x2e	“i2c::LCD”	?
7	2	0x40	“i2c::DEB”	?
8	2	0x44	“i2c::DEB”	?
9	3	0xa6	“i2c::HID”	Gyroscope. The device table in I2C-module had the device address changed from 0xA6 to 0xD6 with 8.0.0-18.
10	3	0xd0	“i2c::HID”	Gyroscope (old3DS)
11	3	0xd2	“i2c::HID”	Gyroscope (2DS, new3DSXL, new2DSXL)
12	3	0xa4	“i2c::HID”	DebugPad (slightly modified 🔗 Wii Classic Controller Pro)
13	3	0x9a	“i2c::IR”	IR
14	3	0xa0	“i2c::EEP”	HWCAL EEPROM ( only present on dev units where SHA256 is used for HWCAL verification)
15	2	0xee	“i2c::NFC”	New3DS-only NFC
16	1	0x40	“i2c::QTM”	New3DS-only QTM
17	3	0x54	“i2c::IR”	Used by IR-module starting with 8.0.0-18, for New3DS-only HID via “ir:rst”. This deviceid doesn’t seem to be supported by i2c module on 8.0.0-18(actual support was later added in New3DS i2c module).

Notice: These device addresses are used for writing to the respective device, for reading bit0 must be set (see I2C protocol). Thus, the actual device address is >> 1.

Device 3 #

 ro = read-only (writing is no-op)
 rw = read-write
 wo = write-only (reading will yield 00, FF, or unpredictable data)

 d* = dynamic register (explaination below this table)
 s* = shared register (explaination below this table)
 ds = dynamic shared (explaination below this table)

Reading or writing multiple bytes from/to single-byte registers increments the register ID along with it. For example reading two bytes from reg 0x00 reads regs 0x00 and 0x01.

This is not the case for multibyte regs (0x29, 0x2D, 0x4F, 0x61 and 0x7F), plus reg 0x60.

0x00 s ro Version high

0x01 s ro Version low

0x02

For bit0 and 1 values, writing will mask away/"acknowledge" the event, set to 3 by mcuMainLoop on reset if reset source is Watchdog

bit0: RTC clock value got reset to defaults
bit1: Watchdog reset happened
bit5: TWL MCU reg: volume mode (0: 8-step, 1: 32-step)
bit6: TWL MCU reg: NTR (0) vs TWL mode (1)
bit7: TWL MCU reg: Uses NAND

0x03 ds rw Top screen Vcom

0x04 ds rw Bottom screen Vcom

0x05 - 0x07 s rw Danger zone - MCU unlock sequence is written here.

0x08 s ro Raw 3D slider position

0x09 s ro Volume slider state (0x00 - 0x3F) This is the same value returned by MCUHWC:GetSoundVolume

0x0A s ro Internal battery temperature (in Celsius)

0x0B

Battery percentage (integer part).

Valid values are in range of 0 to 100 inclusive.

0x0C

Battery percentage (fractional part).

Seems to have a resolution of around 0.1% according to tests.

To calculate battery charge percentage in full resolution:

MCU[0x0B] + (MCU[0x0C] / 256.0F)

0x0D

System voltage.

This voltage seems to be measured at the load side, so the voltage reading will always be lower than direct probes across the battery due to the various voltage drops in the system by the time the voltage is measured.

To calculate system voltage in Volts:

MCU[0x0D] * 5 / 256.0F

0x0E s ro ?

0x0F

Flags: bit7-5 are read via mcu::GPU. The rest of them are read via mcu::RTC.

bit1: ShellState
bit3: AdapterState
bit4: BatteryChargeState
bit5: Bottom screen backlight on
bit6: Top screen backlight on
bit7: LCD panel voltage on

0x10 - 0x13 s ro Received interrupt bitmask, see register 0x18 for possible values If no interrupt was received this register is 0

0x14 s ro Unused and unwritable byte :(

0x15 - 0x17 s rw Unused and unreferenced free RAM! Good for userdata.

0x18 - 0x1B

Interrupt mask for register 0x10 (0=enabled,1=disabled)

bit00: Power button press (for 27 "ticks")
bit01: Power button held (for 375 "ticks"; the 3DS turns off regardless after a fixed time)
bit02: HOME button press (for 5 "ticks")
bit03: HOME button release
bit04: WiFi switch button
bit05: Shell close
bit06: Shell open
bit07: Fatal hardware condition(?) (sent when the MCU gets reset by the Watchdog timer)
bit08: Charger removed
bit09: Charger plugged in
bit10: RTC alarm (when some conditions are met it's sent when the current day and month and year matches the current RTC time)
bit11: Accelerometer I2C read/write done 1
bit12: HID update
bit13: Battery percentage status change (triggered at 10%, 5%, and 0% while discharging)
bit14: Battery stopped charging (independent of charger state)
bit15: Battery started charging

Nonmaskable(?) interrupts

bit16: ???
bit17: ??? (opposite even for bit16)
bit22: Volume slider position change
bit23: ??? Register 0x0E update
bit24: GPU off
bit25: GPU on
bit26: bottom backlight off
bit27: bottom backlight on
bit28: top backlight off
bit29: top backlight on
bit30: bit set by mcu sysmodule
bit31: bit set by mcu sysmodule

0x1C - 0x1F s rw Unused and unreferenced free RAM! Good for userdata.

0x20

System power control:

bit0: power off
bit1: full reboot (unused). Discards things like CFG9_BOOTENV
   - Asserts RESET1 via PMIC command (?) (deasserts nRESET1). This could be the reset that controls some CFG9 registers
   - Asserts RESET2 (P0.1 = 0, PM0.1 = 0 (output)) (deasserts nRESET2)
   - Asserts FCRAM_RESET (P3.0 = 0) (deasserts nFCRAM_RESET)
bit2: normal reboot. Preserves CFG9_BOOTENV, etc.
   - Asserts RESET2 (P0.1 = 0, PM0.1 = 0)
   - If in NTR emulation mode (see reg 0x02), asserts FCRAM_RESET (P3.0 = 0)
   - Resets TWL MCU i2c registers
bit3: FCRAM reset (present in by LgyBg. Unused because a system reboot does the same thing & a PDN reg also possibly implements this function)
   - Asserts FCRAM_RESET (P3.0 = 0)
bit4: signal that sleep mode is about to be entered (used by PTM)

Bit 4 sets a bit at a RAM address which seems to control the watcdog timer state, then this bit is immediately unmasked. This field has a bitmask of 0x0F.

If any of the reset bits is set, the MCU waits for 5ms, then deasserts RESET1 (via PMIC), RESET2 (PM0.1 = 1 (input)) and FCRAM_RESET (P3.0 = 1), and reinitializes some other various registers after a 100ms delay.

0x21

Used in legacy mode to signal events for TWL MCU "emulation" (written to REG[0x5D])? Software then asserts the TWL MCU IRQ pin via Legacy I/O registers.

bit0: Signal TWL POWER button click
bit1: Signal TWL reset
bit2: Signal TWL power off
bit3: Signal TWL battery low
bit4: Signal TWL battery empty
bit5: Signal TWL volume button click

0x22

Used to turn on or turn off LCD-related boost circuits. Bits 5:2 can be read back so see whether backlight setting is in progress or not, however bits 1:0 get cleared as soon as the request gets acknowledged.

bit0: LCD panel voltage off
bit1: LCD panel voltage on
bit2: Bottom screen backlight off
bit3: Bottom screen backlight on
bit4: Top screen backlight off
bit5: Top screen backlight on

Bits 4 and 5 have no effect on a 2DS because the backlight source is the bottom screen. The rest of the bits are masked away.

0x23 d wo Writing 0x72 ('r') resets the MCU, but this is stubbed on retail?

0x24 s rw Watchdog timer. This must be set *before* the timer is triggered, otherwise the old value is used. Value zero disables the watchdog.

0x25 s rw ?

0x26 s rw ?

0x27 sd rw Raw volume slider state

0x28 s rw Brightness of the WiFi/Power LED

0x29

sd(5)

Power mode indicator state (read-write)

1 = forced default blue
2 = sleep mode animation
3 = "power off" mode
4 = disable blue power LED and turn on red power LED
5 = disable red power LED and turn on blue power LED
6 = animate blue power LED off and flash red power LED
anything else = automatic mode

The other 4 bytes (32bits) affect the pattern of the red power LED (write only)

0x2A s rw WiFi LED state, non-0 value turns on the WiFi LED, 4 bits wide

0x2B

Camera LED state, 4bits wide,

0, 3, 6-0xF = off
1 = slowly blinking
2 = constantly on
3 = "TWL" mode
4 = flash once
5 = delay before changing to 2

0x2C s rw 3D LED state, 4 bits wide

0x2D 0x64 wo This is used for controlling the notification LED (see MCURTC:SetInfoLEDPatternHeader as well), when this register is written. It's possible to write data here with size less than 0x64, and only that portion of the pattern data will get overwritten. Reading from this register only returns zeroes, so it's considered write-only. Writing past the size of this register seems to do nothing.

0x2E s ro This returns the notification LED status when read (1 means new cycle started)

0x2F s wo? ??? The write function for this register is stubbed.

0x30 - 0x36

RTC time (system clock). 7 bytes are read from this. The upper nibble of each byte encodes 10s (BCD), so each byte is post-processed with (byte & 0xF) + (10 * (byte >> 4)).

byte 0: seconds
byte 1: minutes
byte 2: hours
byte 3: current week (unused)
byte 4: days
byte 5: months
byte 6: years

0x37 s rw RTC time byte 7: leap year counter / "watch error correction" register (unused in code)

0x38 - 0x3C

RTC alarm registers

byte 0: minutes
byte 1: hours
byte 2: day
byte 3: month
byte 4: year

0x3B s rw Could be used on extremely old MCU_FIRM versions to upload MCU firmware if reg 0xF == 0 and reg 0x10 == 1 (presumably major and minor version fields for mcufw 0.1 which largely predates factory firm).

0x3D 0x3E ds ro RTC tick counter / "ITMC" (when resets to 0 the seconds increase) Only reading 0x3D will update the in-RAM value

0x3F

2 bits

bit0: Asserts RESET1 (P0.0 = 0, PM0.0 = 0 (output)) but does NOT deassert it (wtf?). This seems to kill the entire SoC: is it because it doesn't deassert it, or does it not deassert it because the SoC hangs anyway? This is the pin that controls some security-critical regs like CFG9_BOOTENV!
bit1: turns on a prohibited bit in an RTC Control register and turns P12 into an output

0x40 s rw Tilt sensor sampling mode. Bits 0 and 1 control the mode. If bits 0 or 1 are set then the tilt sensor is enabled and sampled.

0x41 s rw Index selector for register 0x44

0x42 s rw Unused?

0x43 s rw Unused???, accelometer related

0x44 s rw ???, pedoometer related(?)

0x45 - 0x4A

Tilt sensor 3D rotation from the 12bit ADC, left shifted 4 to fit in a 16bit signed short, relative to the 3DS bottom screen

AXIS	V=0x00	V=0x40	V=0xC0
X (left/right)	held up vertically	rotated left 90° like a steering wheel	rotated right 90° like a steering wheel
Y (forwards/backwards)	laid flat on the desk with the screen facing up	held up vertically	held up vertically with screen facing upside-down
Z (???)	???	???	???

0x4B s rw PedometerStepCount (for the current day)

0x4C 0x4D ?? ?? ??

0x4E d rw ??? this = (0xFFE9E & 1) ? 0x10 : 0

0x4F d(6) ro

0x50 s rw ???

0x51 s rw ???

0x52 - 0x57 s rw ?

0x58 s rw Register-mapped ADC register DSP volume slider 0% volume offset (setting this to 0xFF will esentially mute the DSP as it's the volume slider's maximum raw value)

0x59 s rw Register-mapped ADC register DSP volume slider 100% volume offset (setting both this and the above to 0 will disable the volume slider with 100% volume, setting this to a lower value than the above will make the volume slider have only 2 states; on and off)

0x5A s ro/rw Invalid, do not use! On newer MCU_FIRM versions this is unused, but on older MCU_FIRM versions this is a read-only counter.

0x5B - 0x5F s - These registers are out of bounds (0xFFC00 and up), they don't exist, writing is no-op, reading will yield FFs.

0x60

Free register bank address (index) select Selects the index to read from in the free register bank, up to 200. Used in conjunction with reg 0x61.

byte 0: bit0 = "WirelessDisabled", bit1 = "SoftwareClosed", bit2 = "PowerOffInitiated", bit3 = "LgyNativeResolution", bit4 = "LegacyJumpProhibited"
byte 1: Legacy LCD data
bytes 2 and 3: Local Friend Code counter
bytes 4 and 5: UUID clock sequence
bytes 6 and 7: Unused
bytes 8 to 175: Playtime data for legacy titles
bytes 176 to 188: Temporary playtime data in case console doesn't shut down gracefully, updated every 5 minutes
bytes 188 to 199: Unused

0x61

d(200)

Free register bank, data is read from/written to here.

Accessing N bytes of this register increments the selected index by N.

0x62 - 0x7E s - These registers don't exist, writing is no-op, reading will yield FFs.

0x7F

d(9-0x13)

Various system state information (debug pointer table)

byte 0x00: Console type, see here
byte 0x01: PMIC vendor code
byte 0x02: Battery vendor code (determined from battery middle pin)
   0x00: Maxell (middle pin tied to GND)
     CTR-003 CTR-A-BP (old3DS)
     CTR-003 CTR-A-BPMX-C3 (2DS): Wuxi Hitachi Maxell Co.,Ltd.
     CTR-003 CTR-A-BPMX-C5 (Switch Pro Controller): Wuxi Maxell Co., Ltd.
     SPR-003 SPR-A-BPMX-C3 (new3DSXL): Wuxi Hitachi Maxell Co.,Ltd.
byte 0x03: MGIC version (major?)
byte 0x04: MGIC version (minor?)
byte 0x05: RCOMP(?)
byte 0x06: On-board battery slot NTC reading (more heat causes this value to go *down*, and cooling off will make this value go back up)
byte 0x09: system model (see Cfg:GetSystemModel for values)
byte 0x0A: Red Power LED mode (0 = off, 1 = on)
byte 0x0B: Blue Power LED intensity  (0x00 - 0xFF)
byte 0x0D: RGB LED red intensity
byte 0x0E: RGB LED green intensity
byte 0x0F: RGB LED blue intensity
byte 0x11: WiFi LED brightness
byte 0x12: raw button states?
   bit0: unset while Power button is held
   bit1: unset while HOME button is held
   bit2: unset while WiFi slider is held
   bit5: unset while the charging LED is active
   bit6: unset while charger is plugged in

On MCU_FIRM major version 1 the size of this is 9, reading past the 9th byte will yield AA instead of FF.

0x80 - 0xFF s - These registers don't exist, writing is no-op, reading will yield FFs.

Shared register: the letter “s” means that the given register is in a “shared register pool”, meaning the resgister is in the register pool in RAM at address 0xFFBA4 + registernumber.

Dynamic register: these registers aren’t in the shared pool, they just “pretend” to be there. These registers often don’t retain their set value, change rapidly, or control various hardware.

Non-shared (dynamic) register: it’s a register whose contents separate from the shared register pool. Messing with these registers will not affect the shared register pool at all.

On old versions of MCU_FIRM none of the invalid registers are masked away by the read handler function, but are still read-only. Newer MCU_FIRM versions return the hardcoded value FF instead.

Device 5 & 6 #

These are the chip-on-glass display controllers, also known as I2CLCD.

Shared registers #

These registers are the same across all known I2CLCD controllers (except Controller ID 0x00).

Register	Name	Valid bits	Description
0x01	Display enable	0x11	Values: `- 0x00 - screen off, slow burn-in` `- 0x01 - screen off, fast burn-in` `- 0x10 - screen on, color input used` `- 0x11 - screen on, color input not used, High-Z (display turns black or white depending on interface config)`
0x40	Read address		Write to this register to set the read address. Reading from I2CLCD is non-standard. When you read, it returns pairs of the currently read address, and then the data byte at that address. The read address auto-increments.
0x54	Checksum? trigger	0x01	When transitioning bit0 from 0 to 1, it seems to trigger some sort of checksum calcuation. Broken on controller 0x01, where it's oneshot.
0x55	???	0x03 (all) / 0x07 (2DS)	Unknown. When toggling 0x54 bit0 from 0 to 1, this register gets changed to 0x01 (all) / 0x05 (2DS). This register is sometimes seen with a value of 0x02 at initialization time on the top screen.
0x56	Checksum?		Unknown. Read-writable with no effect (old3DS) / read-only (all). A random value is written here when 0x54 bit0 is changed from 0 to 1. Constantly updates with a seemingly random value, except on Controller ID 0x01, where it's oneshot/bugged.
0x60	???	0x01	Unknown. 0x00 is written here during init. Seems to have no effect.
0x61	Register checksum		Some - but not all - register values are combined using an unknown algorithm into this register. It's unknown which registers influence this value, as some registers which influence this value are read-only.
0x62	???	0x01	Unknown, does nothing on known controllers. During init, gsp waits for this to become 0x01.
0xFE	???		Unknown, does nothing. 0xAA is written here during init.
0xFF	Controller ID		Upper 4bits is manufacturer. Lower 4bits is unknown, most likely revision, possibly encoded as a Johnson counter. The fields are encoded this way, most likely for the register checksum feature. Manufacturers: `- 0x0 - SHARP (LTPS(?) TN), old I2CLCD, found in old3DS (non-XL) only` `- 0x1 - JDI (LTPS IPS), found in select new3DS and new3DSXL consoles` `- 0xC - SHARP (LTPS(?) TN), new I2CLCD` `- 0xE - SHARP (TFT), found in 2DS only` Known IDs: `- 0xC7 - new3DS, new3DSXL, new2DSXL, and some select newer old3DSXL` `- 0xC3 - older old3DSXL` `- 0xE1 - 2DS` `- LQ050B1LW10B` `- LQ = normal TFT` `- 050 = panel 5 inches diagonal` `- B = "other" display format` `- 1 = transmissive (backlight-compatible)` `- L = LVDS` `- W = unknown coating type` `- 10 = model number` `- B = unknown suffix` `- 0x10 - some select new3DS and new3DSXL with IPS screens` `- 0x01 - old3DS` `- LS035T7LE38P (top screen)` `- LS = TFT (LTPS or SI-TFT ?)` `- 035 = panel 3.5 inches diagonal` `- T = "other 16:9" (even though the panel is 16:10 in physical size, or 32:10 in terms of pixel count)` `- 7 = unknown backing type` `- L = LVDS` `- E = unknown coating type` `- 38 = model number` `- P = unknow suffix` `- LS030Q7DW48P (bottom screen)` `- LS = TFT (LTPS or SI-TFT ?)` `- 030 = panel 3 inches diagonal` `- Q = QVGA (320x240)` `- 7 = unknown backing type` `- D = parallel RGB (unspecified, but it's known to be RGB888 for this display)` `- W = unknown coating type` `- 48 = model number` `- P = unknow suffix` `- 0x00 - no controller, or dead (I2CLCD always ACKs reads, but returns 00 if dead)`

Custom registers for controller 0x00 #

This Controller ID is fully unknown, and the only reason we know about its existance is due to gsp having special handling code for it.

Register	Name	Valid bits	Description
0x11	???		Unknown. Write 0x10 to initialize.
0x50	???		Unknown. Write 0x01 to initialize.

Custom registers for controller 0x01 #

Register	Name	Valid bits	Description
0x10	Interface config	0xF7	Regonfigures the input pins and pin behavior of the controller. `bit0 - color value invert (D = ~D, or D = 255 - D)` `bit1 - color format remap (D7:D2 <-- D5:D0, that is left shift color data by 2)` `bit2 - ???` `bit4 - ???` `bit5 - ???` `bit6 - ???` `bit7 - DS-style undriven screen (it will be white instead of black, see shared register 0x01)`
0x11	Image config	0x7F	Image filters and pixel clock control. `bit0 - Horizontal Flip (scan from right to left)` `bit1 - red-blue swap` `bit2 - ???` `bit3 - ???` `bit4 - ???` `bit5 - ???` `bit6 - ???`
0x1D	???	0x0F	Unknown, bit0 enables registers 0x12 to 0x19 to control some analog timing controls to the display panel itself.
0x50	???	0x11	Unknown. Has no effect on bottom screen. On the top screen, bit4 blanks out the display (LVDS disable?).
0x53	???	0x73	Unknown. While other bits seem to have no effect, bit0 kills the controller until a power cycle.

Custom registers for controller 0xC3 #

Basically the same as Controller ID 0xC7.

Custom registers for controller 0xC7 #

This is the most common non-old3DS display controller. Quite overclockable.

Note: on the 0xC7 controller unlocking the factory controls at register 0x03 glitches out most of the standard controls (like registers 0x50 to 0x56), so use with caution.

Register	Name	Valid bits	Description
0x03	Factory key 2		Write 0xAA here to unlock a second set of factory controls.
0xAF	Factory key		Write 0xAA here to unlock factory controls.

Factory mode registers for unlock register 0x03:

Register	Name	Valid bits	Description
0x10	Image control?	0xD7	Most bits are unknown. `bit0 - color invert` `bit1 - slight gamma increase`
0x11	Image transform?	0x7F	Mostly unknown. `bit0 - Invert horizontal scan direction (0 = left to right, 1 = right to left)` `bit1 - red-blue swap` `bit2 - Invert vertical scan direction (0 = top to bottom, 1 = bottom to top)` `bit3 - Invert the order of each scanline pair (might be needed if bit2 is toggled)` `bit4 - Enable interlaced signal (use bit3 to swap fields)` `bit5 - ???` `bit6 - ???`
0x70-0x83	Color curve red		These registers are used for fine-tuning the analog driving curve of the screen Positive: `- byte 00 (0xFF) - ???` `- byte 01 (0xFF) - ???` `- byte 02 (0x3F) - ???` `- byte 03 (0x3F) - ???` `- byte 04 (0x3F) - ???` `- byte 05 (0x3F) - ???` `- byte 06 (0x3F) - ???` `- byte 07 (0x3F) - ???` `- byte 08 (0x3F) - ???` `- byte 09 (0x3F) - ???` Negative: `- byte 10 (0xFF) - ???` `- byte 11 (0xFF) - ???` `- byte 12 (0x3F) - ???` `- byte 13 (0x3F) - ???` `- byte 14 (0x3F) - ???` `- byte 15 (0x3F) - ???` `- byte 16 (0x3F) - ???` `- byte 17 (0x3F) - ???` `- byte 18 (0x3F) - ???` `- byte 19 (0x3F) - ???`
0x84-0x97	Color curve green
0x98-0xAB	Color curve blue

Custom registers for controller 0xE1 #

This controller is designed to drive a split panel. As such, the factory controls have been slightly altered to accomodate this.

This is the only I2CLCD which responds on both I2CLCD addresses. The dominant screen is the bottom one.

Most registers are similar to controller 0xC7, but there are some differences due to the split shared panel nature.

Register	Name	Valid bits	Description
0x03	Factory key 2		Write 0xAA here to unlock a 2nd set of factory controls.
0xAF	Factory key		Write 0xAA here to unlock factory controls.

Factory mode registers for unlock register 0x03:

Register	Name	Valid bits	Description
0x10	Image control?	0xD7	Most bits are unknown. This applies to the whole display panel. `bit0 - color invert` `bit1 - slight gamma increase`
0x11	Image transform	0x33	`bit0 - top half horizontal flip` `bit1 - top half red-blue swap` `bit4 - bottom half horizontal flip` `bit5 - bottom half red-blue swap`
0x70-0x83	Analog curve top		Consists of two unknown curve values. Seems to be nonstandard. Pair 1: `byte 00 (0xFF) - ???` `byte 01 (0xFF) - ???` `byte 02 (0xFF) - ???` `byte 03 (0xFF) - ???` `byte 04 (0x3F) - ???` `byte 05 (0x3F) - ???` `byte 06 (0x3F) - ???` `byte 07 (0x3F) - ???` `byte 08 (0x3F) - ???` `byte 09 (0x3F) - ???` Part 2: `byte 10 (0xFF) - ???` `byte 11 (0xFF) - ???` `byte 12 (0xFF) - ???` `byte 13 (0xFF) - ???` `byte 14 (0x3F) - ???` `byte 15 (0x3F) - ???` `byte 16 (0x3F) - ???` `byte 17 (0x3F) - ???` `byte 18 (0x3F) - ???` `byte 19 (0x3F) - ???`
0x84-0x97	Analog curve bottom

Custom registers for controller 0x10 #

JDI IPS controller.

Warning: on the JDI controller, unlocking any of the factory mode registers overshadows some other registers, so don’t write to “standard” locations (other than register 0x40) before locking factory mode back!

Register	Name	Valid bits	Description
0x03	Factory key 2		Write 0xAA here to unlock advanced IPS curve controls.
0xAF	Factory key		Write 0xAA here to unlock factory controls.

Factory mode registers unlocked by register 0xAF:

0x41 - 0x4F
0x58 - 0x5F
0x67 - 0x6F
0xD0 - 0xEF
unknown…

Factory mode registers unlocked by register 0x03:

0x04 - 0x0F
unknown…

Register	Name	Valid bits	Description
0x70-0x7F	Driving curve 1-1
0x80-0x8F	Driving curve 1-2
0x90-0x9F	Driving curve 2-1
0xA0-0xAF	Driving curve 2-2
0xB0-0xBF	Driving curve 3-1
0xC0-0xCF	Driving curve 3-2

Device 10 #

See the datasheet linked to on the Hardware page for reference.

Device 11 #

See the datasheet linked to on the Hardware page for reference.

Device 12 #

REGISTER	WIDTH	DESCRIPTION
0x0	21	DebugPad state.

This is a 🔗 Wii Classic Controller Pro which was slightly modified to have an encrypted device type of 0xF0 🔗 instead of 0xFD.

See here for the HID shared memory report format.

Device 13 #

Raw I2C register address	Internal register address	Width	Description
0x0	0x0	0x40	RHR / THR (data receive/send FIFO)
0x8	0x1	0x1	IER
0x10	0x2	0x1	FCR/IIR
0x18	0x3	0x1	LCR
0x20	0x4	0x1	MCR
0x28	0x5	0x1	LSR
0x30	0x6	0x1	MSR/TCR
0x38	0x7	0x1	SPR/TLR
0x40	0x8	0x1	TXLVL
0x48	0x9	0x1	RXLVL
0x50	0xA	0x1	IODir
0x58	0xB	0x1	IOState
0x60	0xC	0x1	IoIntEna
0x68	0xD	0x1	reserved
0x70	0xE	0x1	IOControl
0x78	0xF	0x1	EFCR

See the 🔗 datasheet linked to on the Hardware page for reference. From that datasheet, for the structure of the I2C register address u8: “Bit 0 is not used, bits 2:1 select the channel, bits 6:3 select one of the UART internal registers. Bit 7 is not used with the I2C-bus interface, but it is used by the SPI interface to indicate a read or a write operation.”

Device 14 #

Used by Cfg-sysmodule via the i2c::EEP service. This is presumably EEPROM going by the service name.

The Cfg-module code which loads the CCAL(nandro:/sys/{HWCAL0.dat/HWCAL1.dat}) file from NAND will load it from I2C instead, if a certain state flag is non-zero. Likewise for the function which writes CCAL to NAND. HMAC/hash verification after loading is skipped when the CCAL was loaded from I2C.

Device 15 #

This the New3DS NFC controller “I2C” interface. This device is accessed via the WriteDeviceRaw/ReadDeviceRaw I2C service commands.

Since the *Raw commands are used with this, this device has no I2C registers. Instead, raw data is transfered after the I2C device is selected. Hence, WriteDeviceRaw is used for sending commands to the controller, while ReadDeviceRaw is for receiving responses from the controller. Certain commands may return multiple command responses.

Command request / response structure:

Offset	Size	Description
0x0	0x1	Normally 0x10?
0x1	0x1	Command source / destination.
0x2	0x1	CmdID
0x3	0x1	Payload size.

Following the above header is the payload data(when payload size is non-zero), with the size specified in the header. The command response payload is usually at least 1-byte, where that byte appears to be normally 0x0. For command requests the payload data is the command parameters.

For command requests sent to the NFC tag itself, Cmd[1]=0x0 and CmdID=0x0. The command request payload data here is the actual command request data for the NFC tag, starting with the CmdID u8 at payload+0.

During NFC module startup, a certain command is sent to the controller which eventually(after various cmd-reply headers etc) returns the following the payload after the first byte in the payload:

000000: 44 65 63 20 32 32 20 32 30 31 32 31 34 3a 35 33  Dec 22 201214:53 
000010: 3a 35 30 01 05 0d 46 05 1b 79 20 07 32 30 37 39  :50...F..y .2079
000020: 31 42 35                                         1B5

Or that is: “Dec 22 201214:53:5020791B5”. Therefore, this appears to return the part-number of the NFC controller(other command request(s) / response(s) use this part-number value too).

NFC controller commands #

CmdRequest[1]	CmdID	Payload data for parameters	Description
0x2E	0x2F	Firmware image for this chunk, size varies.	This is used during NFC module startup to upload the firmware image to the NFC controller. This is used repeatedly to upload multiple chunks of the image.

Device 17 #

(Stub)

Used by New 3DS for ZL, ZR, C stick

This device do not use registers. After writing the address, read the next several bytes.

Offset	Description
0x0	Fixed 0x80
0x1	Buttons (ZL = 0x4, ZR = 0x2)

I2C Registers