| CMSIS-Driver Version 2.02 Peripheral Interface for Middleware and Application Code

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SPI Interface

Driver API for SPI Bus Peripheral (Driver_SPI.h) More...

## Content
| Status Error Codes
| Negative values indicate errors (SPI has specific codes in addition to common Status Error Codes).
| SPI Events
| The SPI driver generates call back events that are notified via the function ARM_SPI_SignalEvent.
| SPI Control Codes
| Many parameters of the SPI driver are configured using the ARM_SPI_Control function.

## Data Structures
struct | ARM_DRIVER_SPI
| Access structure of the SPI Driver. More...
struct | ARM_SPI_CAPABILITIES
| SPI Driver Capabilities. More...
struct | ARM_SPI_STATUS
| SPI Status. More...

## Typedefs
typedef void(* | ARM_SPI_SignalEvent_t )(uint32_t event)
| Pointer to ARM_SPI_SignalEvent : Signal SPI Event.

## Functions
ARM_DRIVER_VERSION | ARM_SPI_GetVersion (void)
| Get driver version.
ARM_SPI_CAPABILITIES | ARM_SPI_GetCapabilities (void)
| Get driver capabilities.
int32_t | ARM_SPI_Initialize (ARM_SPI_SignalEvent_t cb_event)
| Initialize SPI Interface.
int32_t | ARM_SPI_Uninitialize (void)
| De-initialize SPI Interface.
int32_t | ARM_SPI_PowerControl (ARM_POWER_STATE state)
| Control SPI Interface Power.
int32_t | ARM_SPI_Send (const void *data, uint32_t num)
| Start sending data to SPI transmitter.
int32_t | ARM_SPI_Receive (void *data, uint32_t num)
| Start receiving data from SPI receiver.
int32_t | ARM_SPI_Transfer (const void *data_out, void *data_in, uint32_t num)
| Start sending/receiving data to/from SPI transmitter/receiver.
uint32_t | ARM_SPI_GetDataCount (void)
| Get transferred data count.
int32_t | ARM_SPI_Control (uint32_t control, uint32_t arg)
| Control SPI Interface.
ARM_SPI_STATUS | ARM_SPI_GetStatus (void)
| Get SPI status.
void | ARM_SPI_SignalEvent (uint32_t event)
| Signal SPI Events.

## Description

Driver API for SPI Bus Peripheral (Driver_SPI.h)

The Serial Peripheral Interface Bus (SPI) implements a synchronous serial bus for data exchange. In microcontroller (MCU) applications, the interface is often used to connect peripheral components at board (PCB) level. SPI devices can operate as Master (SCLK and SS are outputs) or Slave (SCLK and SS are inputs). Wikipedia offers more information about the Serial Peripheral Interface Bus.

SPI Structure

The SPI Driver API defines a SPI interface for middleware components. The SPI Driver supports multiple slaves, but if only one slave is connected, then the Slave Select signal can be omitted.

SPI Master connected to a single slave

SPI Master connected to 3 slaves

The SPI Driver functions control the following SPI signal lines.

Signal | Name | Description
--- | --- | ---
SS | Slave Select (active low) | Selects the slave. This signal can be part of the SPI peripheral or implemented using a GPIO pin.
MOSI | Master Out, Slave In | MOSI output of the Master connects to MOSI input of the Slave.
SCLK | Serial Clock | Serial clock output from Master. Controls the transfer speed and when data are sent and read.
MISO | Master In, Slave Out | MISO input of the Master connects to MISO output of the Slave.

SPI API

The following header files define the Application Programming Interface (API) for the SPI interface:

- Driver_SPI.h : Driver API for SPI Bus Peripheral

The driver implementation is a typical part of the Device Family Pack (DFP) that supports the peripherals of the microcontroller family.

Driver Functions

The driver functions are published in the access struct as explained in Driver Functions

- ARM_DRIVER_SPI : access struct for SPI driver functions

Example Code

The following example code shows the usage of the SPI interface.

#include "Driver_SPI.h"
#include "cmsis_os.h" // ARM::CMSIS:RTOS:Keil RTX
void mySPI_Thread(void const *argument);
osThreadId tid_mySPI_Thread;
/* SPI Driver */
extern ARM_DRIVER_SPI Driver_SPI0;
void mySPI_callback(uint32_t event)
{
switch (event)
{
case ARM_SPI_EVENT_TRANSFER_COMPLETE:
/* Success: Wakeup Thread */
osSignalSet(tid_mySPI_Thread, 0x01);
break;
case ARM_SPI_EVENT_DATA_LOST:
/* Occurs in slave mode when data is requested/sent by master
but send/receive/transfer operation has not been started
and indicates that data is lost. */
__breakpoint(0); /* Error: Call debugger or replace with custom error handling */
break;
case ARM_SPI_EVENT_MODE_FAULT:
/* Occurs in master mode when Slave Select is deactivated and
indicates Master Mode Fault. */
__breakpoint(0); /* Error: Call debugger or replace with custom error handling */
break;
}
}
/* Test data buffers */
const uint8_t testdata_out[8] = { 0, 1, 2, 3, 4, 5, 6, 7 };
uint8_t testdata_in [8];
void mySPI_Thread(void const* arg)
{
ARM_DRIVER_SPI* SPIdrv = &Driver_SPI0;
osEvent evt;
#ifdef DEBUG
ARM_DRIVER_VERSION version;
ARM_SPI_CAPABILITIES drv_capabilities;
version = SPIdrv->GetVersion();
if (version.api < 0x200) /* requires at minimum API version 2.00 or higher */
{ /* error handling */
return;
}
drv_capabilities = SPIdrv->GetCapabilities();
if (drv_capabilities.event_mode_fault == 0)
{ /* error handling */
return;
}
#endif
/* Initialize the SPI driver */
SPIdrv->Initialize(mySPI_callback);
/* Power up the SPI peripheral */
SPIdrv->PowerControl(ARM_POWER_FULL);
/* Configure the SPI to Master, 8-bit mode @10000 kBits/sec */
SPIdrv->Control(ARM_SPI_MODE_MASTER | ARM_SPI_CPOL1_CPHA1 | ARM_SPI_MSB_LSB | ARM_SPI_SS_MASTER_SW | ARM_SPI_DATA_BITS(8), 10000000);
/* Set CS line */
SPIdrv->Control(ARM_SPI_CONTROL_SS, ARM_SPI_SS_INACTIVE);
/* Clear CS line */
SPIdrv->Control(ARM_SPI_CONTROL_SS, ARM_SPI_SS_ACTIVE);
/* thread loop */
while (1)
{
/* Transmit some data */
SPIdrv->Send(testdata_out, sizeof(testdata_in));
/* Wait for completion */
evt = osSignalWait(0x01, 100);
if (evt.status == osEventTimeout) {
__breakpoint(0); /* Timeout error: Call debugger */
}
/* Receive 8 bytes of reply */
SPIdrv->Receive(testdata_in, 8);
osSignalWait(0x01, 100);
if (evt.status == osEventTimeout) {
__breakpoint(0); /* Timeout error: Call debugger */
}
}
}

## Data Structure Documentation

struct ARM_DRIVER_SPI

Access structure of the SPI Driver.

The functions of the SPI driver are accessed by function pointers exposed by this structure. Refer to Driver Functions for overview information.

Each instance of a SPI interface provides such an access structure. The instance is identified by a postfix number in the symbol name of the access structure, for example:

- Driver_SPI0 is the name of the access struct of the first instance (no. 0).
- Driver_SPI1 is the name of the access struct of the second instance (no. 1).

A middleware configuration setting allows connecting the middleware to a specific driver instance Driver_SPIn. The default is 0, which connects a middleware to the first instance of a driver.

### Data Fields
ARM_DRIVER_VERSION(* | GetVersion )(void)
| Pointer to ARM_SPI_GetVersion : Get driver version.
ARM_SPI_CAPABILITIES(* | GetCapabilities )(void)
| Pointer to ARM_SPI_GetCapabilities : Get driver capabilities.
int32_t(* | Initialize )(ARM_SPI_SignalEvent_t cb_event)
| Pointer to ARM_SPI_Initialize : Initialize SPI Interface.
int32_t(* | Uninitialize )(void)
| Pointer to ARM_SPI_Uninitialize : De-initialize SPI Interface.
int32_t(* | PowerControl )(ARM_POWER_STATE state)
| Pointer to ARM_SPI_PowerControl : Control SPI Interface Power.
int32_t(* | Send )(const void *data, uint32_t num)
| Pointer to ARM_SPI_Send : Start sending data to SPI Interface.
int32_t(* | Receive )(void *data, uint32_t num)
| Pointer to ARM_SPI_Receive : Start receiving data from SPI Interface.
int32_t(* | Transfer )(const void *data_out, void *data_in, uint32_t num)
| Pointer to ARM_SPI_Transfer : Start sending/receiving data to/from SPI.
uint32_t(* | GetDataCount )(void)
| Pointer to ARM_SPI_GetDataCount : Get transferred data count.
int32_t(* | Control )(uint32_t control, uint32_t arg)
| Pointer to ARM_SPI_Control : Control SPI Interface.
ARM_SPI_STATUS(* | GetStatus )(void)
| Pointer to ARM_SPI_GetStatus : Get SPI status.

#### Field Documentation

int32_t(* Control)(uint32_t control, uint32_t arg)

Pointer to ARM_SPI_Control : Control SPI Interface.

ARM_SPI_CAPABILITIES(* GetCapabilities)(void)

Pointer to ARM_SPI_GetCapabilities : Get driver capabilities.

uint32_t(* GetDataCount)(void)

Pointer to ARM_SPI_GetDataCount : Get transferred data count.

ARM_SPI_STATUS(* GetStatus)(void)

Pointer to ARM_SPI_GetStatus : Get SPI status.

ARM_DRIVER_VERSION(* GetVersion)(void)

Pointer to ARM_SPI_GetVersion : Get driver version.

int32_t(* Initialize)(ARM_SPI_SignalEvent_t cb_event)

Pointer to ARM_SPI_Initialize : Initialize SPI Interface.

int32_t(* PowerControl)(ARM_POWER_STATE state)

Pointer to ARM_SPI_PowerControl : Control SPI Interface Power.

int32_t(* Receive)(void *data, uint32_t num)

Pointer to ARM_SPI_Receive : Start receiving data from SPI Interface.

int32_t(* Send)(const void *data, uint32_t num)

Pointer to ARM_SPI_Send : Start sending data to SPI Interface.

int32_t(* Transfer)(const void *data_out, void *data_in, uint32_t num)

Pointer to ARM_SPI_Transfer : Start sending/receiving data to/from SPI.

int32_t(* Uninitialize)(void)

Pointer to ARM_SPI_Uninitialize : De-initialize SPI Interface.

struct ARM_SPI_CAPABILITIES

SPI Driver Capabilities.

A SPI driver can be implemented with different capabilities. The bitfield members of this struct encode the capabilities implemented by this driver.

Returned by:

- ARM_SPI_GetCapabilities

Data Fields
uint32_t | event_mode_fault: 1 | Signal Mode Fault event: ARM_SPI_EVENT_MODE_FAULT.
uint32_t | microwire: 1 | supports Microwire Interface
uint32_t | simplex: 1 | supports Simplex Mode (Master and Slave)
uint32_t | ti_ssi: 1 | supports TI Synchronous Serial Interface

struct ARM_SPI_STATUS

SPI Status.

Structure with information about the status of the SPI. The bitfields encode busy flag and error flags.

Returned by:

- ARM_SPI_GetStatus

Data Fields
uint32_t | busy: 1 | Transmitter/Receiver busy flag.
uint32_t | data_lost: 1 | Data lost: Receive overflow / Transmit underflow (cleared on start of transfer operation)
uint32_t | mode_fault: 1 | Mode fault detected; optional (cleared on start of transfer operation)

## Typedef Documentation

ARM_SPI_SignalEvent_t

Pointer to ARM_SPI_SignalEvent : Signal SPI Event.

Provides the typedef for the callback function ARM_SPI_SignalEvent.

Parameter for:

- ARM_SPI_Initialize

## Function Documentation

int32_t ARM_SPI_Control | ( | uint32_t | control,
|  | uint32_t | arg
| ) |  |

Control SPI Interface.

Parameters

  [in] | control | Operation
  [in] | arg | Argument of operation (optional)

Returns
  common Status Error Codes and driver specific Status Error Codes

Controls the SPI interface settings and executes various operations.

The parameter control is a bit mask that specifies various operations (see tables below). The control bits of the various groups can be combined to a control code as shown in the following example. Depending on the control bits, the parameter arg provides additional information, for example the baudrate.

Example

extern ARM_DRIVER_SPI Driver_SPI0;
// configure: SPI master | clock polarity=1, clock phase=1 | bits per frame=16 | bus speed : 1000000
status = Driver_SPI0.Control(ARM_SPI_MODE_MASTER |
ARM_SPI_CPOL1_CPHA1 |
ARM_SPI_DATA_BITS(16), 1000000);

ARM_SPI_MODE_xxx specifies the SPI mode.

Mode Control Bits | Description
--- | ---
ARM_SPI_MODE_INACTIVE | Set SPI to inactive.
ARM_SPI_MODE_MASTER | Set the SPI Master (Output on MOSI, and the Input on MISO); arg = Bus Speed in bps
ARM_SPI_MODE_SLAVE | Set the SPI Slave (Output on MISO, and the Input on MOSI)
ARM_SPI_MODE_MASTER_SIMPLEX | Set the SPI Master (Output and Input on MOSI); arg = Bus Speed in bps
ARM_SPI_MODE_SLAVE_SIMPLEX | Set the SPI Slave (Output and Input on MISO)

ARM_SPI_CPOLx_CPHAy specifies the clock polarity and clock phase. Additional parameters ARM_SPI_TI_SSI and ARM_SPI_MICROWIRE specify special formats.

Mode Parameters: Frame Format | Description
--- | ---
ARM_SPI_CPOL0_CPHA0 | CPOL=0 and CPHA=0: Clock Polarity 0, Clock Phase 0 (default)
ARM_SPI_CPOL0_CPHA1 | CPOL=0 and CPHA=1: Clock Polarity 0, Clock Phase 1
ARM_SPI_CPOL1_CPHA0 | CPOL=1 and CPHA=0: Clock Polarity 1, Clock Phase 0
ARM_SPI_CPOL1_CPHA1 | CPOL=1 and CPHA=1: Clock Polarity 1, Clock Phase 1
ARM_SPI_TI_SSI | Specifies that the frame format corresponds to the Texas Instruments Frame Format
ARM_SPI_MICROWIRE | Specifies that the frame format corresponds to the National Microwire Frame Format

ARM_SPI_DATA_BITS(x) specifies the number of bits transferred per SPI frame.

Mode Parameters: Data Bits | Description
--- | ---
ARM_SPI_DATA_BITS(n) | Set the number of bits per SPI frame; the possible range for n is 1..32.

ARM_SPI_MSB_LSB and ARM_SPI_LSB_MSB specify the bit order.

Mode Parameters: Bit order | Description
--- | ---
ARM_SPI_MSB_LSB | Set the bit order from MSB to LSB (default)
ARM_SPI_LSB_MSB | Set the bit order from LSB to MSB

ARM_SPI_SS_MASTER_xxx and ARM_SPI_SS_SLAVE_xxx specify the Slave Select mode.

Mode Parameters: Slave Select Mode | Description
--- | ---
ARM_SPI_SS_MASTER_UNUSED | Set the Slave Select mode for the master to Not used (default)
ARM_SPI_SS_MASTER_SW | Set the Slave Select mode for the master to Software controlled
ARM_SPI_SS_MASTER_HW_OUTPUT | Set the Slave Select mode for the master to Hardware controlled Output
ARM_SPI_SS_MASTER_HW_INPUT | Set the Slave Select mode for the master to Hardware monitored Input
ARM_SPI_SS_SLAVE_HW | Set the Slave Select mode for the slave to Hardware monitored (default)
ARM_SPI_SS_SLAVE_SW | Set the Slave Select mode for the slave to Software controlled

Miscellaneous Controls execute various operations.

Miscellaneous Controls | Description
--- | ---
ARM_SPI_SET_BUS_SPEED | Set the bus speed in bps; the argument arg specifies the speed value
ARM_SPI_GET_BUS_SPEED | Get the bus speed in bps
ARM_SPI_SET_DEFAULT_TX_VALUE | Set the default transmission value; the argument arg sets the value
ARM_SPI_CONTROL_SS | Control the Slave Select signal; the argument arg: 0=inactive; 1=active
ARM_SPI_ABORT_TRANSFER | Abort the current data transfer

ARM_SPI_CAPABILITIES ARM_SPI_GetCapabilities | ( | void |  | ) |

Get driver capabilities.

Returns
  ARM_SPI_CAPABILITIES

Retrieves information about capabilities in this driver implementation. The bitfield members of the struct ARM_SPI_CAPABILITIES encode various capabilities, for example supported modes.

Example:

extern ARM_DRIVER_SPI Driver_SPI0;
ARM_DRIVER_SPI *drv_info;
void read_capabilities (void) {
ARM_SPI_CAPABILITIES drv_capabilities;
drv_info = &Driver_SPI0;
drv_capabilities = drv_info->GetCapabilities ();
// interrogate capabilities
}

uint32_t ARM_SPI_GetDataCount | ( | void |  | ) |

Get transferred data count.

Returns
  number of data items transferred

Returns the number of currently transferred data items during ARM_SPI_Send, ARM_SPI_Receive and ARM_SPI_Transfer operation.

ARM_SPI_STATUS ARM_SPI_GetStatus | ( | void |  | ) |

Get SPI status.

Returns
  SPI status ARM_SPI_STATUS

Retrieves the current SPI interface status.

ARM_DRIVER_VERSION ARM_SPI_GetVersion | ( | void |  | ) |

Get driver version.

Returns
  ARM_DRIVER_VERSION

Returns version information of the driver implementation in ARM_DRIVER_VERSION

- API version is the version of the CMSIS-Driver specification used to implement this driver.
- Driver version is source code version of the actual driver implementation.

Example:

extern ARM_DRIVER_SPI Driver_SPI0;
ARM_DRIVER_SPI *drv_info;
void setup_spi (void) {
ARM_DRIVER_VERSION version;
drv_info = &Driver_SPI0;
version = drv_info->GetVersion ();
if (version.api < 0x10A) { // requires at minimum API version 1.10 or higher
// error handling
return;
}
}

int32_t ARM_SPI_Initialize | ( | ARM_SPI_SignalEvent_t | cb_event | ) |

Initialize SPI Interface.

Parameters

  [in] | cb_event | Pointer to ARM_SPI_SignalEvent

Returns
  Status Error Codes

The function initializes the SPI interface. It is called when the middleware component starts operation.

The function performs the following operations:

- Initializes the resources needed for the SPI interface.
- Registers the ARM_SPI_SignalEvent callback function.

The parameter cb_event is a pointer to the ARM_SPI_SignalEvent callback function; use a NULL pointer when no callback signals are required.

Example:

- see SPI Interface - Driver Functions

int32_t ARM_SPI_PowerControl | ( | ARM_POWER_STATE | state | ) |

Control SPI Interface Power.

Parameters

  [in] | state | Power state

Returns
  Status Error Codes

Allows you to control the power modes of the SPI interface.

int32_t ARM_SPI_Receive | ( | void * | data,
|  | uint32_t | num
| ) |  |

Start receiving data from SPI receiver.

Parameters

  [out] | data | Pointer to buffer for data to receive from SPI receiver
  [in] | num | Number of data items to receive

Returns
  Status Error Codes

This functions is used to only receive data (transmits the default value as specified by ARM_SPI_Control with ARM_SPI_SET_DEFAULT_TX_VALUE as control parameter).

The function parameters specify the buffer for data and the number of items to receive. The item size is defined by the data type which depends on the configured number of data bits.

Data type is:

- uint8_t when configured for 1..8 data bits
- uint16_t when configured for 9..16 data bits
- uint32_t when configured for 17..32 data bits

Calling the function ARM_SPI_Receive only starts the receive operation. The function is non-blocking and returns as soon as the driver has started the operation (driver typically configures DMA or the interrupt system for continuous transfer). When in slave mode the operation is only registered and started when the master starts the transfer. During the operation it is not allowed to call this function or any other data transfer function again. Also the data buffer must stay allocated. When receive operation is completed (requested number of items received) the ARM_SPI_EVENT_TRANSFER_COMPLETE event is generated. Progress of receive operation can also be monitored by reading the number of items already received by calling ARM_SPI_GetDataCount.

Status of the receiver can also be monitored by calling the ARM_SPI_GetStatus and checking the busy flag which indicates if reception is still in progress or pending.

When in master mode and configured to monitor slave select and the slave select gets deactivated during transfer then the SPI mode changes to inactive and the ARM_SPI_EVENT_MODE_FAULT event is generated (instead of ARM_SPI_EVENT_TRANSFER_COMPLETE).

When in slave mode but send/receive/transfer operation is not started and data is sent/requested by the master then the ARM_SPI_EVENT_DATA_LOST event is generated.

Receive operation can be aborted by calling ARM_SPI_Control with ARM_SPI_ABORT_TRANSFER as the control parameter.

int32_t ARM_SPI_Send | ( | const void * | data,
|  | uint32_t | num
| ) |  |

Start sending data to SPI transmitter.

Parameters

  [in] | data | Pointer to buffer with data to send to SPI transmitter
  [in] | num | Number of data items to send

Returns
  Status Error Codes

This functions is used to only send data to the SPI transmitter (received data is ignored).

The function parameters specify the buffer with data and the number of items to send. The item size is defined by the data type which depends on the configured number of data bits.

Data type is:

- uint8_t when configured for 1..8 data bits
- uint16_t when configured for 9..16 data bits
- uint32_t when configured for 17..32 data bits

Calling the function ARM_SPI_Send only starts the send operation. When in slave mode the operation is only registered and started when the master starts the transfer. The function is non-blocking and returns as soon as the driver has started the operation (driver typically configures DMA or the interrupt system for continuous transfer). During the operation it is not allowed to call this function or any other data transfer function again. Also the data buffer must stay allocated and the contents of unsent data must not be modified. When send operation is completed (requested number of items sent) the ARM_SPI_EVENT_TRANSFER_COMPLETE event is generated. Progress of send operation can also be monitored by reading the number of items already sent by calling ARM_SPI_GetDataCount.

Status of the transmitter can also be monitored by calling the ARM_SPI_GetStatus and checking the busy flag which indicates if transmission is still in progress or pending.

When in master mode and configured to monitor slave select and the slave select gets deactivated during transfer then the SPI mode changes to inactive and the ARM_SPI_EVENT_MODE_FAULT event is generated (instead of ARM_SPI_EVENT_TRANSFER_COMPLETE).

When in slave mode but send/receive/transfer operation is not started and data is sent/requested by the master then the ARM_SPI_EVENT_DATA_LOST event is generated.

Send operation can be aborted by calling ARM_SPI_Control with ARM_SPI_ABORT_TRANSFER as the control parameter.

void ARM_SPI_SignalEvent | ( | uint32_t | event | ) |

Signal SPI Events.

Parameters

  [in] | event | SPI Events notification mask

Returns
  none

The function ARM_SPI_SignalEvent notifies the application of the SPI Events and it is registered by the function ARM_SPI_Initialize. The function ARM_SPI_GetCapabilities returns information about the implemented optional events in a driver.

The argument event represents the notification mask of the events. Each event is coded in a separate bit and therefore it is possible to signal multiple events in the event call back function. The following call back notifications are generated:

Bit | Event | Description
--- | --- | ---
0 | ARM_SPI_EVENT_TRANSFER_COMPLETE | Occurs after call to ARM_SPI_Send, ARM_SPI_Receive or ARM_SPI_Transfer to indicate that all the data has been transferred. The driver is ready for the next transfer operation.
1 | ARM_SPI_EVENT_DATA_LOST | Occurs in slave mode when data is requested/sent by master but send/receive/transfer operation has not been started and indicates that data is lost.
2 | ARM_SPI_EVENT_MODE_FAULT | Occurs in master mode when Slave Select is deactivated and indicates Master Mode Fault.

int32_t ARM_SPI_Transfer | ( | const void * | data_out,
|  | void * | data_in,
|  | uint32_t | num
| ) |  |

Start sending/receiving data to/from SPI transmitter/receiver.

Parameters

  [in] | data_out | Pointer to buffer with data to send to SPI transmitter
  [out] | data_in | Pointer to buffer for data to receive from SPI receiver
  [in] | num | Number of data items to transfer

Returns
  Status Error Codes

This functions is used to transfer data via SPI. It synchronously sends data to the SPI transmitter and receives data from the SPI receiver.

The function parameters specify the buffer with data to send, the buffer for data to receive and the number of items to transfer. The item size is defined by the data type which depends on the configured number of data bits.

Data type is:

- uint8_t when configured for 1..8 data bits
- uint16_t when configured for 9..16 data bits
- uint32_t when configured for 17..32 data bits

Calling the function ARM_SPI_Transfer only starts the transfer operation. The function is non-blocking and returns as soon as the driver has started the operation (driver typically configures DMA or the interrupt system for continuous transfer). When in slave mode the operation is only registered and started when the master starts the transfer. During the operation it is not allowed to call this function or any other data transfer function again. Also the data buffers must stay allocated and the contents of unsent data must not be modified. When transfer operation is completed (requested number of items transferred) the ARM_SPI_EVENT_TRANSFER_COMPLETE event is generated. Progress of transfer operation can also be monitored by reading the number of items already transferred by calling ARM_SPI_GetDataCount.

Status of the transmitter and receiver can also be monitored by calling the ARM_SPI_GetStatus and checking the busy flag.

When in master mode and configured to monitor slave select and the slave select gets deactivated during transfer then the SPI mode changes to inactive and the ARM_SPI_EVENT_MODE_FAULT event is generated (instead of ARM_SPI_EVENT_TRANSFER_COMPLETE).

When in slave mode but send/receive/transfer operation is not started and data is sent/requested by the master then the ARM_SPI_EVENT_DATA_LOST event is generated.

Transfer operation can also be aborted by calling ARM_SPI_Control with ARM_SPI_ABORT_TRANSFER as the control parameter.

int32_t ARM_SPI_Uninitialize | ( | void |  | ) |

De-initialize SPI Interface.

Returns
  Status Error Codes

The function ARM_SPI_Uninitialize de-initializes the resources of SPI interface.

It is called when the middleware component stops operation and releases the software resources used by the interface.