Detailed Description

SPI driver implementation for a USCIB peripheral using the micro DMA controller.

============================================================================

The SPI header file should be included in an application as follows:

Refer to SPI.h for a complete description of APIs & example of use.

This SPI driver implementation is designed to operate on a UCSI controller in SPI mode. It uses the APIs for a USCIB controller.

SPI Chip Select

The SPIUSCIBDMA operates the controller in 3-pin mode; therefore it is not safe to use in a multi-master SPI bus environment. It is the application's responsibility to assert and de-assert a GPIO pin for chip select purposes.

Chip select type	SPI_MASTER mode	SPI_SLAVE mode
Hardware chip select	Not available on this peripheral.
Software chip select	The application is responsible to ensure that correct SPI slave is selected before performing a SPI_transfer().	Up to the application's implementation.

DMA Interrupts

The MSP430 DMA controller uses a single interrupt vector to handle all DMA related IRQ. Because of the "shared" nature, of the DMA's ISR, this driver implementation provides a simple ISR function SPIUSCIBDMA_hwiIntFxn() which needs to be called from within the DMA's ISR. SPIUSCIBDMA_hwiIntFxn() will only service DMA channel interrupts that are associated with the SPI_Handle. Each SPIUSCIBDMA instance will require a call from within the DMA's ISR.

SPI_Handle spi0uscidma;
SPI_Handle spi1uscidma;
// As this DMA controller uses a single interrupt vector for all DMA
// channels (regardless of the triggering source), its left up to the user
// to call SPI_serviceISR() to service its associated DMA channels.
void myDMAISR(UArg arg)
{
    // Services and clears its assigned DMA channel interrupts
    SPI_serviceISR(spi0uscidma);
    // Services and clears its assigned DMA channel interrupts
    SPI_serviceISR(spi1uscidma);
    // some other user application code that's not related to the SPI driver,
    // but is used to service remaining DMA channels
}
spi0uscidma = SPI_open(someSPI_configIndexValue, &params);
...
spi1uscidma = SPI_open(someSPI_configIndexValue, &params);
....

SPI data frames

The USCI controller only supports 8-bit data frames.

dataSize	buffer element size
8 bits	uint8_t

DMA transfer size limit

The MSP430 DMA controller supports 2^16 data frames per transfer. Each SPI driver instance requires 2 DMA channels (Tx and Rx) to operate.

DMA accessible memory

Ensure that the txBuf and rxBuf (in SPI_Transaction) point to memory that is accessible by the DMA.

#include <stdint.h>
#include <ti/drivers/SPI.h>
#include <ti/sysbios/knl/Semaphore.h>

Include dependency graph for SPIUSCIBDMA.h:

Go to the source code of this file.

Data Structures
struct	SPIUSCIBDMA_HWAttrs
	SPIUSCIBDMA Hardware attributes. More...

struct	SPIUSCIBDMA_Object
	SPIUSCIBDMA Object. More...

Typedefs
typedef struct SPIUSCIBDMA_HWAttrs	SPIUSCIBDMA_HWAttrs
	SPIUSCIBDMA Hardware attributes. More...

typedef struct SPIUSCIBDMA_Object	SPIUSCIBDMA_Object
	SPIUSCIBDMA Object. More...

typedef struct SPIUSCIBDMA_Object *	SPIUSCIBDMA_Handle

Variables
const SPI_FxnTable	SPIUSCIBDMA_fxnTable

Typedef Documentation

typedef struct SPIUSCIBDMA_HWAttrs SPIUSCIBDMA_HWAttrs

SPIUSCIBDMA Hardware attributes.

These fields are used by driverlib APIs and therefore must be populated by driverlib macro definitions. For MSP430Ware these definitions are found in:

inc/hw_memmap.h
usci_b_spi.h
dma.h

A sample structure is shown below:

 uint8_t spiUSCIBDMAscratchBuf;
 const SPIUSCIBDMA_HWAttrs spiUSCIBDMAHWAttrs[] = {
     {
         .baseAddr = USCI_B1_BASE,
         .clockSource = USCI_B_SPI_CLOCKSOURCE_SMCLK,
         .bitOrder = USCI_B_SPI_MSB_FIRST,
         .scratchBufPtr = &spiUSCIBDMAscratchBuf,
         .defaultTxBufValue = 0,
 
         // DMA base address
         .dmaBaseAddr = DMA_BASE,
         // Rx Channel
         .rxDMAChannelIndex = DMA_CHANNEL_1,
         .rxDMASourceTrigger = DMA_TRIGGERSOURCE_22,
         // Tx Channel
         .txDMAChannelIndex = DMA_CHANNEL_0,
         .txDMASourceTrigger = DMA_TRIGGERSOURCE_23
     },
 };

typedef struct SPIUSCIBDMA_Object SPIUSCIBDMA_Object

SPIUSCIBDMA Object.

The application must not access any member variables of this structure!

typedef struct SPIUSCIBDMA_Object * SPIUSCIBDMA_Handle

Variable Documentation

const SPI_FxnTable SPIUSCIBDMA_fxnTable