I2C

The I2C interface connects the LCD, audio amplifier and camera to the CPU.

There are two possible I2C controllers. If the LSB of register 0xF0000000 is 0x41, the gamepad has the Samsung controller, otherwise it has the Renesas controller.

In practice, I have only seen Renesas controllers so far, so I don't know how rare the Samsung one is.

There are 4 I2C busses, referred to as 1, 2, 3 and 4. Bus 1 appears to be for slave mode, while the others are for master mode. In practice, all the I2C devices are on bus 3, leaving the others unused.

The I2C registers are distributed as follows:

Base address	Desc.
0xF0005800	General I2C registers
0xF0005C00	Bus 1
0xF0006000	Bus 2
0xF0006400	Bus 3
0xF0006800	Bus 4

General registers

These registers control the individual busses.

Address	Desc.
0xF0005800	IRQ flags
0xF0005804	Bus enable
0xF0005808	IRQ acknowledge

In each register, bit0..3 corresponds to bus 1..4.

Renesas controller

Slave mode (bus 1)

Offset	Desc.
0x104	??
0x108	??
0x138	Data 0
0x13C	Data 1

Master mode (bus 2..4)

Offset	Desc.
0x004	Data input/output
0x008	Transfer control
0x018	Transfer status
0x020	Status register

Base+0x004

Data input/output.

Base+0x008

Transfer control.

Bits	Desc.
0	Stop
1	??
2	Read mode
3	Write mode
4	Start
5	Request data (when reading)

Bit 0 appears to be write-only.

Bit 5 gets cleared after a data byte is received.

TODO: bit 5 is also set at the end of a read??

Base+0x018

Transfer status.

Bits	Desc.
0	Stop
1	Start
2	Ack (from remote)
3	Direction; 0=reading, 1=writing
7	Transfer pending

Samsung controller

Slave mode (bus 1)

TODO

Master mode (bus 2..4)

Offset	Desc.
0x000	Transfer control??
0x004	??
0x00C	Data input/output
0x010	??