Hardware/SMC
General
The Wii U added a new chip to assist with power management alongside the RTC, labeled "SMC". The SMC is responsible for managing disc drive power/eject, power LED patterns, wireless resets, regulator enable/PGOOD monitoring, and possibly other unknown functionality.
Communication
SMC resides as device ID 0x50 on I2C bus 3. It communicates at 5kHz in IOS and 10KHz in Cafe2Wii?
Registers
SMC has two types of registers: Read/write and command-based. Read/write registers operate by having the register number written (1 byte), followed by either another written byte, or a 1 byte read. Command-based registers perform their action just by writing the register number (1 byte). When attempting to read a command-based register, it will read as 0xFF. Some registers will change themselves to read 0x97 if you attempt to write to them.
| Index | Type | Description |
|---|---|---|
| 0x00 | Command | ODD On |
| 0x01 | Command | ODD Off |
| 0x02 | Command | ODD Eject Request |
| 0x8D | Read/Write? | 00 on power on? |
| 0x8E | Read/Write? | 00 on power on? |
| 0x8F | Read/Write? | 00 on power on? |
| 0x10 | Command | ON LED on |
| 0x11 | Command | ON LED on? |
| 0x12 | Command | ON LED off |
| 0x13 | Command | ON LED pulse |
| 0x14 | Command | CC LED off |
| 0x15 | Command | CC LED on |
| 0x16 | Command | CC LED pulse |
| 0x17 | ? | ? |
| 0x18 | ? | ? |
| 0x19 | ? | ? |
| 0x1A | ? | ? |
| 0x1B | ? | ? |
| 0x1C | ? | ? |
| 0x1D | ? | ? |
| 0x1E | Command | OFF LED on |
| 0x1F | Command | OFF LED pulse |
| 0x20 | Command | bt_rst |
| 0x21 | Command | wifi_rst |
| 0x22 | Command | drc_wifi_rst |
| 0x30 | Read/Write | TimerCounter, changes to 0x97 on write. |
| 0x31 | ? | ? Changes to 0x97 on write. |
| 0x32 | ? | ? Changes to 0x97 on write. |
| 0x40 | Read/Write | ProgramRevision (val: 0xC5) |
| 0x41 | Read/Write | SystemEventFlag, read-only |
| 0x42 | Read/Write | ?, read-only (val: 0x0B, 0x0A?) |
| 0x43 | Read/Write | USB Power (bitmask; front USB: 0x1, rear USB: 0x2) |
| 0x44 | Read/Write | NotificationLED, current LED state. (bitmask: 0x97?) |
| 0x45 | Read/Write | PowerFailureState (val: 0x08) |
| 0x46 | Read/Write | WifiRstCtrl (val: 0x00), changes to 0x97 on write. |
| 0x47 | Read/Write | ? not writable (val: 0xFF) |
| 0x48 | Read/Write | ? not writable (val: 0x0F) |
| 0x60 | Read/Write | LAPSSetting (val: 0x00), changes to 0x97 on write. |
| 0x61~0x70 | Read/Write | SystemError, read-only (val: 0x00) |
| 0x62~0x70 | Read/Write | ? (val: 0x00) |
| 0x71 | Command? | Blinks the drive LED? Causes 0x1C bytes to read as 0xFF. |
| 0x72 | Read/Write? | ? (val: 0x00) |
| 0x73 | Read/Write? | ? (val: 0x00) |
| 0x74 | Read/Write? | ? (val: 0x00) |
| 0x75 | Read/Write? | ? (val: 0x00) |
| 0x76 | Read/Write? | ? (val: 0x00) |
| 0x80~0xFF | Read/Write? | ? (val: 0x00) |
SystemEventFlag
| Bitmask | Name |
|---|---|
| 0x40 | SMC_POWER_BUTTON |
| 0x20 | SMC_EJECT_BUTTON |
| 0x10 | SMC_DISK_INSERT |
| 0x08 | SMC_TIMER |
| 0x04 | SMC_BT_IRQ |
| 0x02 | SMC_WAKE0 |
| 0x01 | SMC_WAKE1 |
NotificationLED
Kinda bitmaskey but also not really?
| Value | Name |
|---|---|
| 0x97 | Some error condition? Happens if you write 0xFF or 0x00. |
| 0x80 | bitmask? sticky |
| 0x30 | Blue LED pulse |
| 0x20 | Blue LED on |
| 0x08 | Red LED on |
| 0x03 | Yellow LED pulse |
| 0x02 | Yellow LED on |