Unit SPI

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The SPI protocol is not defined by any actual standard but some psuedo standards exist with all of the available devices. SPI is a master-slave protocol where the master asserts the chip selectline (CS) to select the slave device before sending data one byte at a time. For every byte written to the bus by the master the selected slave returns a byte as well so for every write there is an equivalent read. SPI can also operate in either 4 wire (standard) or 3 wire(bidirectional) modes.

Due to the lack of formal standards and the range of devices that exist various options are provided to allow setting clock phase and polarity as well chip select polarity.

For the purpose of this interface a device is the SPI controller attached to the local system and may be either a master or a slave. Since the protocol does not include any form of enumeration or identification the interface does not attempt to represent the devices connected to the bus, any driver written to communicate with a connected SPI device should know (or allow configuration of) the chip select for the for the device and the specific message format required for that device.

`SPI_FLAG_NONE = $00000000;`
`SPI_FLAG_SLAVE = $00000001;`	Device is a slave not a master
`SPI_FLAG_4WIRE = $00000002;`	Device supports 4 wire operation (CS/MISO/MOSI/SCLK)
`SPI_FLAG_3WIRE = $00000004;`	Device supports 3 wire operation (CS/MIMO/SCLK)
`SPI_FLAG_LOSSI = $00000008;`	Device supports LoSSI (Low Speed Serial) mode (CS/SCL/SDA)
`SPI_FLAG_CPOL = $00000010;`	Device supports Clock Polarity setting
`SPI_FLAG_CPHA = $00000020;`	Device supports Clock Phase setting
`SPI_FLAG_CSPOL = $00000040;`	Device supports Chip Select Polarity setting
`SPI_FLAG_NO_CS = $00000080;`	Device supports Chip Select None (CS handled externally)
`SPI_FLAG_DMA = $00000100;`	Device supports DMA transfers

`SPI_TRANSFER_NONE = $00000000;`
`SPI_TRANSFER_DMA = $00000001;`	Use DMA for transfer (Write/Read) (Note: Buffers must be DMA compatible)

`SPI_LOG_LEVEL_DEBUG = LOG_LEVEL_DEBUG;`	SPI debugging messages
`SPI_LOG_LEVEL_INFO = LOG_LEVEL_INFO;`	SPI informational messages, such as a device being attached or detached
`SPI_LOG_LEVEL_ERROR = LOG_LEVEL_ERROR;`	SPI error messages
`SPI_LOG_LEVEL_NONE = LOG_LEVEL_NONE;`	No SPI messages

SPI	The SPI device to start
Mode	The device mode to set (eg SPI_MODE_4WIRE)
ClockRate	The clock rate to set for the device
ClockPhase	The clock phase to set (eg SPI_CLOCK_PHASE_LOW)
ClockPolarity	The clock polarity to set (eg SPI_CLOCK_POLARITY_LOW)
Return	ERROR_SUCCESS if completed or another error code on failure

SPI	The SPI device to stop
Return	ERROR_SUCCESS if completed or another error code on failure

SPI	The SPI device to read ?rom
ChipSelect	The chip select for the slave to read ?rom (eg SPI_CS_0)
Dest	Pointer to a buffer to receive the data
Size	The size of the buffer
Flags	The flags for this transfer (eg SPI_TRANSFER_DMA)
Count	The number of bytes read on return
Return	ERROR_SUCCESS if completed or another error code on failure
Note	Because SPI writes and then reads for each byte, dummy data will be written for each byte to be read}

SPI	The SPI device to write to
ChipSelect	The chip select for the slave to write to (eg SPI_CS_0)
Source	Pointer to a buffer of data to transmit
Size	The size of the buffer
Flags	The flags for this transfer (eg SPI_TRANSFER_DMA)
Count	The number of bytes written on return
Return	ERROR_SUCCESS if completed or another error code on failure
Note	Because SPI writes and then reads for each byte, received data will be discarded for each by written

SPI	The SPI device to write to and read ?rom
ChipSelect	The chip select for the slave to write to and read ?rom (eg SPI_CS_0)
Source	Pointer to a buffer of data to transmit
Dest	Pointer to a buffer to receive the data
Size	The size of the buffer
Flags	The flags for this transfer (eg SPI_TRANSFER_DMA)
Count	The number of bytes written and read on return
Return	ERROR_SUCCESS if completed or another error code on failure
Note	Because SPI writes and then reads for each byte, both the source and dest buffers must be the same size

SPI	The SPI device to get device mode ?rom
Return	The device mode or SPI_MODE_UNKNOWN on failure

SPI	The SPI device to set device mode for
Mode	The device mode to set (eg SPI_MODE_4WIRE)
Return	ERROR_SUCCESS if completed or another error code on failure

`SPI_STATE_DISABLED = 0;`
`SPI_STATE_ENABLED = 1;`

SPI	The SPI device to get clock rate ?rom
ChipSelect	The chip select number to get clock rate ?rom (SPI_CS_NONE for default)
Return	The clock rate in Hz or 0 on failure

SPI	The SPI device to set clock rate for
ChipSelect	The chip select number to set clock rate for (SPI_CS_NONE for default)
ClockRate	The clock rate to set in Hz
Return	ERROR_SUCCESS if completed or another error code on failure

SPI	The SPI device to get clock phase ?rom
Return	The clock phase or SPI_CLOCK_PHASE_UNKNOWN on failure

SPI	The SPI device to set clock phase for
ClockPhase	The clock phase to set (eg SPI_CLOCK_PHASE_LOW)
Return	ERROR_SUCCESS if completed or another error code on failure

SPI	The SPI device to get clock polarity ?rom
Return	The clock polarity or SPI_CLOCK_POLARITY_UNKNOWN on failure

SPI	The SPI device to set clock polarity for
ClockPolarity	The clock polarity to set (eg SPI_CLOCK_POLARITY_LOW)
Return	ERROR_SUCCESS if completed or another error code on failure

SPI	The SPI device to get chip select polarity ?rom
ChipSelect	The chip select number to get polarity ?rom (SPI_CS_NONE for default)
Return	The chip select polarity or SPI_CS_POLARITY_UNKNOWN on failure

SPI	The SPI device to set chip select polarity for
ChipSelect	The chip select number to set polarity for (SPI_CS_NONE for default)
SelectPolarity	The chip select polarity to set (eg SPI_CS_POLARITY_LOW)
Return	ERROR_SUCCESS if completed or another error code on failure

SPI	The SPI device to get properties ?rom
Properties	Pointer to a TSPIProperties structure to fill in
Return	ERROR_SUCCESS if completed or another error code on failure

Size	Size in bytes to allocate for new SPI (Including the SPI entry)
Return	Pointer to new SPI entry or nil if SPI could not be created

Unit SPI

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ChipSet	The chip select for the slave to read ?rom (eg SPI_CS_0)
Dest	Pointer to a buffer to receive the data
Size	The size of the buffer
Count	The number of bytes read on return
Return	ERROR_SUCCESS if completed or another error code on failure
Note	Because SPI writes and then reads for each byte, dummy data will be written for each byte to be read