DSP Memory Region

The DSP communicates with userland through memory locations 0x1ff40000-0x1ff77fff. Within this region are two areas of structures that are exact duplicates of each other. The DSP alternates between the use of these two areas (much like a double-buffer). Each area has 15 structures within it. The location of these structures can be obtained by reading pipe 2.

The mixer has 24 channels, each of which are individually configurable.

Structure Number	DSP memory address	Size	Description
5	0x8400	0x20	Status (?)
9	0x8410	0x260	Debug (?)
6	0x8540	0x280	Loopback Samples (PCM16)
2	0x8680	0x120	Channel Status (x24)
8	0x9710	0x1A40	?
4	0x9430	0xC4	Main Configuration
7	0x9492	0x1400	?
1	0x9e92	0x1200	Channel Config (x24)
3	0x9430	0x300	GC-ADPCM Coefficients (x24)
10	0xa912	0x200
11	0xaa12	0x180
12	0xaad2	0x300
13	0xac52	0x14
14	0xac5c	0x2476	-
0	0xbfff	0x2	Frame Counter

Channel Config

A 192 byte long structure. There are 24 of them.

Offset	Type	Description
0	u32	Dirty flags
4	70 bytes	TODO
74	u16	Bitmap of which buffers in queue are valid
76	Buffer[4]	Buffer queue
156	u32	-
160	u16	Is Active
162	u16	Config Serial Number (Userland)
164	8	TODO
172	u32	Physical address of current buffer
176	u32	Number of samples in current buffer
180	u16	bits[0:1]: 1 = mono, 2 = stereo; bits[2:3]: buffer format
182	u16	ADPCM predictor
184	s16	ADPCM yn1
186	s16	ADPCM yn2
188	u16	bit[0]: Has ADPCM data?; bit[1]: Is looping?
190	u16	Buffer Id of this current buffer

Buffer

Offset	Type	Description
0	u32	Physical Address
4	u32	Sample Count
8	u16	ADPCM P/S
10	s16[2]	ADPCM yn[1,2]
14	u8	Has ADPCM?
15	u8	Looping?
16	u16	Buffer Id
18	u16	-