Registers
| Old3DS | Name | Address | Width | Used by |
|---|---|---|---|---|
| Yes | I2C1_DATA | 0x10161000 | 1 | |
| Yes | I2C1_CNT | 0x10161001 | 1 | |
| Yes | I2C1_CNTEX | 0x10161002 | 2 | |
| Yes | I2C1_SCL | 0x10161004 | 2 | |
| Yes | I2C2_DATA | 0x10144000 | 1 | |
| Yes | I2C2_CNT | 0x10144001 | 1 | |
| Yes | I2C2_CNTEX | 0x10144002 | 2 | |
| Yes | I2C2_SCL | 0x10144004 | 2 | |
| Yes | I2C3_DATA | 0x10148000 | 1 | |
| Yes | I2C3_CNT | 0x10148001 | 1 | |
| Yes | I2C3_CNTEX | 0x10148002 | 2 | |
| Yes | I2C3_SCL | 0x10148004 | 2 |
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 Devices
| Device id | Device bus id | Device 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" | Unknown. 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 |
| 11 | 3 | 0xd2 | "i2c::HID" | ? |
| 12 | 3 | 0xa4 | "i2c::HID" | DebugPad |
| 13 | 3 | 0x9a | "i2c::IR" | IR |
| 14 | 3 | 0xa0 | "i2c::EEP" | eeprom? |
| 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). |
Device 3
| REGISTER | WIDTH | DESCRIPTION |
|---|---|---|
| 0x03 | 8 | ? |
| 0x04 | 8 | ? |
| 0x09 | 1 | Sound volume: 0x0..0x3F. |
| 0xB | 1 | Battery level: 0x0..0x40. |
| 0x18 | 8 | ? |
| 0x20 | 8 | Writing u8 value 4 here triggers a hardware system reboot. Writing u8 value 1 (repeatedly) triggers a shutdown via power-off? |
| 0x22 | 8 | ? |
| 0x23 | 8 | ? |
| 0x24 | 8 | ? |
| 0x28 | 8 | ? |
| 0x29 | 8 | ? |
| 0x2A | 8 | ? |
| 0x2B | 8 | ? |
| 0x2C | 8 | ? |
| 0x2D | 0x64 | This is used for controlling the notification LED(see MCURTC:SetInfoLEDPatternHeader as well), when this register is written. |
| 0x2E | 1 | This returns the notification LED status when read. |
| 0x30 | 8 | ? |
| 0x31 | 8 | ? |
| 0x32 | 8 | ? |
| 0x33 | 8 | ? |
| 0x34 | 8 | ? |
| 0x35 | 8 | ? |
| 0x36 | 8 | ? |
| 0x37 | 8 | ? |
| 0x38 | 8 | ? |
| 0x39 | 8 | ? |
| 0x3A | 8 | ? |
| 0x3B | 8 | ? |
| 0x3C | 8 | ? |
| 0x41 | 8 | ? |
| 0x43 | 8 | ? |
| 0x4E | 8 | ? |
| 0x50 | 8 | ? |
| 0x51 | 8 | ? |
| 0x58 | 8 | ? |
| 0x60 | 8 | ? |
Device 10
See the datasheet linked to on the Hardware page for reference.
Device 12
| REGISTER | WIDTH | DESCRIPTION |
|---|---|---|
| 0x0 | 21 | DebugPad state. |
This is the DebugPad device, see here.
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 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.
Command request / response structure:
| Offset | Size | Description |
|---|---|---|
| 0x0 | 0x1 | Normally 0x10? |
| 0x1 | 0x1 | ? |
| 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.