SPI Audio

Serial Peripheral Interface (SPI) Audio. More...

Collaboration diagram for SPI Audio:

Classes
class	SPIAudioMaster
	SPI master endpoint for remote audio sink configuration and PCM data transfer. More...
class	SPIAudioSlave
	SPI Audio Slave endpoint matching SPIAudioMaster protocol. More...
class	SPIRegAudioMaster
	SPI master which streams audio to a SPIRegAudioSlave (based on the TinySPISlave library) using its register map: it defines the AudioInfo and the mime type and writes the audio data according to the space which is reported by the available-space register. More...
struct	SPIRegAudioMasterConfig
	Configuration for SPIRegAudioMaster. More...
struct	SPIRegAudioSlaveConfig
	Configuration for SPIRegAudioSlave. More...

Enumerations
enum class	SPIAudioCommand : uint8_t {   SetMime = 1 , SetAudioInfo = 2 , WriteData = 5 , GetAvailableBufferSize = 6 ,   GetFilledBufferSize = 7 , Clear = 8 }
	SPI command ids used by SPIAudioMaster. More...
enum	SPIRegAudioRegister : uint8_t {   SPIREG_NOP = 0x00 , SPIREG_AUDIO_INFO = 0x01 , SPIREG_MIME = 0x02 , SPIREG_AVAILABLE = 0x03 ,   SPIREG_DATA = 0x10 }
	Register map shared by SPIRegAudioMaster and SPIRegAudioSlave. More...

Detailed Description

Serial Peripheral Interface (SPI) Audio.

Author

Phil Schatzmann

Enumeration Type Documentation

SPIAudioCommand

enum class SPIAudioCommand : uint8_t

strong

SPI command ids used by SPIAudioMaster.

Frame format (master -> slave):

• cmd: uint8_t
• payload_len: uint16_t (little endian)
• payload bytes

Response format (slave -> master):

• status: uint8_t (0 = ok)
• response_len: uint16_t (little endian)
• response bytes

Enumerator
SetMime
SetAudioInfo
WriteData
GetAvailableBufferSize
GetFilledBufferSize
Clear

SPIRegAudioRegister

enum SPIRegAudioRegister : uint8_t

Register map shared by SPIRegAudioMaster and SPIRegAudioSlave.

Wire protocol (compatible with the TinySPISlave RegisterMap):

• command byte: bit7 = read, bits 0..6 = register address
• write frame: [cmd][bytes...] (CS low .. CS high)
• read request: [cmd|0x80][n] (n = number of bytes wanted)
• read reply: a second frame in which the master clocks n bytes (0x00) while the slave shifts out the register content. A short pause (CS high) is required between the two frames.

Address 0 is reserved: the dummy bytes clocked by the master during the reply frame are ignored by the slave.

All multi byte values are little endian.

Enumerator
SPIREG_NOP	Reply clocking / no operation.
SPIREG_AUDIO_INFO	8 bytes (rw): sample_rate u32, channels u16, bits_per_sample u8, reserved
SPIREG_MIME	32 bytes (rw): zero terminated mime type
SPIREG_AVAILABLE	4 bytes (ro): u32 free space in the slave audio buffer in bytes
SPIREG_DATA	stream (wo): the bytes of the frame are appended to the audio buffer