A SPI Master, used for communicating with SPI slave devices. More...

#include <SPI.h>

Inheritance diagram for SPI:

Public Member Functions
	SPI (PinName mosi, PinName miso, PinName sclk, PinName ssel=NC)
	Create a SPI master connected to the specified pins. More...

	SPI (PinName mosi, PinName miso, PinName sclk, PinName ssel, use_gpio_ssel_t)
	Create a SPI master connected to the specified pins. More...

	SPI (const spi_pinmap_t &static_pinmap)
	Create a SPI master connected to the specified pins. More...

	SPI (const spi_pinmap_t &static_pinmap, PinName ssel)
	Create a SPI master connected to the specified pins. More...

void	format (int bits, int mode=0)
	Configure the data transmission format. More...

void	frequency (int hz=1000000)
	Set the SPI bus clock frequency. More...

virtual int	write (int value)
	Write to the SPI Slave and return the response. More...

virtual int	write (const char tx_buffer, int tx_length, char rx_buffer, int rx_length)
	Write to the SPI Slave and obtain the response. More...

virtual void	lock (void)
	Acquire exclusive access to this SPI bus. More...

virtual void	unlock (void)
	Release exclusive access to this SPI bus. More...

void	select (void)
	Assert the Slave Select line, acquiring exclusive access to this SPI bus. More...

void	deselect (void)
	Deassert the Slave Select line, releasing exclusive access to this SPI bus. More...

void	set_default_write_value (char data)
	Set default write data. More...

template<typename Type >
int	transfer (const Type tx_buffer, int tx_length, Type rx_buffer, int rx_length, const event_callback_t &callback, int event=SPI_EVENT_COMPLETE)
	Start non-blocking SPI transfer using 8bit buffers. More...

void	abort_transfer ()
	Abort the on-going SPI transfer, and continue with transfers in the queue, if any. More...

void	clear_transfer_buffer ()
	Clear the queue of transfers. More...

void	abort_all_transfers ()
	Clear the queue of transfers and abort the on-going transfer. More...

int	set_dma_usage (DMAUsage usage)
	Configure DMA usage suggestion for non-blocking transfers. More...

Detailed Description

A SPI Master, used for communicating with SPI slave devices.

The default format is set to 8-bits, mode 0, and a clock frequency of 1MHz.

Most SPI devices will also require Chip Select and Reset signals. These can be controlled using DigitalOut pins.

Note: Synchronization level: Thread safe

Example of how to send a byte to a SPI slave and record the response:

#include "mbed.h"
SPI device(SPI_MOSI, SPI_MISO, SPI_SCLK)
DigitalOut chip_select(SPI_CS);
int main() {
    device.lock();
    chip_select = 0;
    int response = device.write(0xFF);
    chip_select = 1;
    device.unlock();
}

Example using hardware Chip Select line:

#include "mbed.h"
SPI device(SPI_MOSI, SPI_MISO, SPI_SCLK, SPI_CS)
int main() {
    device.lock();
    int response = device.write(0xFF);
    device.unlock();
}

Definition at line 98 of file SPI.h.

Constructor & Destructor Documentation

SPI	(	PinName	mosi,
		PinName	miso,
		PinName	sclk,
		PinName	ssel = `NC`
	)

Create a SPI master connected to the specified pins.

Note: This constructor passes the SSEL pin selection to the target HAL. Not all targets support SSEL, so this cannot be relied on in portable code. Portable code should use the alternative constructor that uses GPIO for SSEL.; You can specify mosi or miso as NC if not used.

Parameters

mosi	SPI Master Out, Slave In pin.
miso	SPI Master In, Slave Out pin.
sclk	SPI Clock pin.
ssel	SPI Chip Select pin.

SPI	(	PinName	mosi,
		PinName	miso,
		PinName	sclk,
		PinName	ssel,
		use_gpio_ssel_t
	)

Create a SPI master connected to the specified pins.

Note: This constructor manipulates the SSEL pin as a GPIO output using a DigitalOut object. This should work on any target, and permits the use of select() and deselect() methods to keep the pin asserted between transfers.; You can specify mosi or miso as NC if not used.

Parameters

mosi	SPI Master Out, Slave In pin.
miso	SPI Master In, Slave Out pin.
sclk	SPI Clock pin.
ssel	SPI Chip Select pin.

SPI ( const spi_pinmap_t & static_pinmap )

Create a SPI master connected to the specified pins.

Note: This constructor passes the SSEL pin selection to the target HAL. Not all targets support SSEL, so this cannot be relied on in portable code. Portable code should use the alternative constructor that uses GPIO for SSEL.; You can specify mosi or miso as NC if not used.

Parameters

static_pinmap reference to structure which holds static pinmap.

SPI	(	const spi_pinmap_t &	static_pinmap,
		PinName	ssel
	)

Create a SPI master connected to the specified pins.

Note: This constructor manipulates the SSEL pin as a GPIO output using a DigitalOut object. This should work on any target, and permits the use of select() and deselect() methods to keep the pin asserted between transfers.; You can specify mosi or miso as NC if not used.

Parameters

static_pinmap	reference to structure which holds static pinmap.
ssel	SPI Chip Select pin.

Member Function Documentation

void abort_all_transfers ( )

Clear the queue of transfers and abort the on-going transfer.

void abort_transfer ( )

Abort the on-going SPI transfer, and continue with transfers in the queue, if any.

void clear_transfer_buffer ( )

Clear the queue of transfers.

void deselect ( void )

Deassert the Slave Select line, releasing exclusive access to this SPI bus.

void format	(	int	bits,
		int	mode = `0`
	)

Configure the data transmission format.

Parameters

bits	Number of bits per SPI frame (4 - 32, target dependent).
mode	Clock polarity and phase mode (0 - 3).

mode | POL PHA
-----+--------
  0  |  0   0
  1  |  0   1
  2  |  1   0
  3  |  1   1

void frequency ( int hz = 1000000 )

Set the SPI bus clock frequency.

Parameters

hz	Clock frequency in Hz (default = 1MHz).

virtual void lock ( void )

virtual

Acquire exclusive access to this SPI bus.

void select ( void )

Assert the Slave Select line, acquiring exclusive access to this SPI bus.

If use_gpio_ssel was not passed to the constructor, this only acquires exclusive access; it cannot assert the Slave Select line.

void set_default_write_value ( char data )

Set default write data.

SPI requires the master to send some data during a read operation. Different devices may require different default byte values. For example: A SD Card requires default bytes to be 0xFF.

Parameters

data	Default character to be transmitted during a read operation.

int set_dma_usage ( DMAUsage usage )

Configure DMA usage suggestion for non-blocking transfers.

Parameters

usage The usage DMA hint for peripheral.

Returns: Result of the operation.

Return values

0	The usage was set.
-1	Usage cannot be set as there is an ongoing transaction.

int transfer	(	const Type *	tx_buffer,
		int	tx_length,
		Type *	rx_buffer,
		int	rx_length,
		const event_callback_t &	callback,
		int	event = `SPI_EVENT_COMPLETE`
	)

Start non-blocking SPI transfer using 8bit buffers.

This function locks the deep sleep until any event has occurred.

Parameters

tx_buffer	The TX buffer with data to be transferred. If NULL is passed, the default SPI value is sent.
tx_length	The length of TX buffer in bytes.
rx_buffer	The RX buffer which is used for received data. If NULL is passed, received data are ignored.
rx_length	The length of RX buffer in bytes.
callback	The event callback function.
event	The event mask of events to modify.

See also: spi_api.h for SPI events.

Returns: Operation result.

Return values

0	If the transfer has started.
-1	If SPI peripheral is busy.

Definition at line 259 of file SPI.h.

virtual void unlock ( void )

virtual

Release exclusive access to this SPI bus.

virtual int write ( int value )

virtual

Write to the SPI Slave and return the response.

Parameters

value Data to be sent to the SPI slave.

Returns: Response from the SPI slave.

virtual int write	(	const char *	tx_buffer,
		int	tx_length,
		char *	rx_buffer,
		int	rx_length
	)

virtual

Write to the SPI Slave and obtain the response.

The total number of bytes sent and received will be the maximum of tx_length and rx_length. The bytes written will be padded with the value 0xff.

Parameters

tx_buffer	Pointer to the byte-array of data to write to the device.
tx_length	Number of bytes to write, may be zero.
rx_buffer	Pointer to the byte-array of data to read from the device.
rx_length	Number of bytes to read, may be zero.

Returns: The number of bytes written and read from the device. This is maximum of tx_length and rx_length.

Public Member Functions

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

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