SPI: Serial Peripheral Interface

Overview

The MCUXpresso SDK provides a peripheral driver for the Serial Peripheral Interface (SPI) module of MCUXpresso SDK devices.

SPI driver includes functional APIs and transactional APIs.

Functional APIs are feature/property target low level APIs. Functional APIs can be used for SPI initialization/configuration/operation for optimization/customization purpose. Using the functional API requires the knowledge of the SPI peripheral and how to organize functional APIs to meet the application requirements. All functional API use the peripheral base address as the first parameter. SPI functional operation groups provide the functional API set.

Transactional APIs are transaction target high level APIs. Transactional APIs can be used to enable the peripheral and in the application if the code size and performance of transactional APIs satisfy the requirements. If the code size and performance are a critical requirement, see the transactional API implementation and write a custom code. All transactional APIs use the spi_handle_t as the first parameter. Initialize the handle by calling the SPI_MasterTransferCreateHandle() or SPI_SlaveTransferCreateHandle() API.

Transactional APIs support asynchronous transfer. This means that the functions SPI_MasterTransferNonBlocking() and SPI_SlaveTransferNonBlocking() set up the interrupt for data transfer. When the transfer completes, the upper layer is notified through a callback function with the kStatus_SPI_Idle status.

Typical use case

SPI master transfer using an interrupt method

#define BUFFER_LEN (64)
spi_master_handle_t spiHandle;
spi_master_config_t masterConfig;
spi_transfer_t xfer;
volatile bool isFinished = false;

const uint8_t sendData[BUFFER_LEN] = [......];
uint8_t receiveBuff[BUFFER_LEN];

void SPI_UserCallback(SPI_Type *base, spi_master_handle_t *handle, status_t status, void *userData)
{
    isFinished = true;
}

void main(void)
{
    //...

    SPI_MasterGetDefaultConfig(&masterConfig);

    SPI_MasterInit(SPI0, &masterConfig, srcClock_Hz);
    SPI_MasterTransferCreateHandle(SPI0, &spiHandle, SPI_UserCallback, NULL);

    // Prepare to send.
    xfer.txData = sendData;
    xfer.rxData = receiveBuff;
    xfer.dataSize = sizeof(sendData);

    // Send out.
    SPI_MasterTransferNonBlocking(SPI0, &spiHandle, &xfer);

    // Wait send finished.
    while (!isFinished)
    {
    }

    // ...
}

SPI Send/receive using a DMA method

#define BUFFER_LEN (64)
spi_dma_handle_t spiHandle;
dma_handle_t g_spiTxDmaHandle;
dma_handle_t g_spiRxDmaHandle;
spi_config_t masterConfig;
spi_transfer_t xfer;
volatile bool isFinished;

uint8_t sendData[BUFFER_LEN] = ...;
uint8_t receiveBuff[BUFFER_LEN];

void SPI_UserCallback(SPI_Type *base, spi_dma_handle_t *handle, status_t status, void *userData)
{
    isFinished = true;
}

void main(void)
{
    //...

    // Initialize DMA peripheral
    DMA_Init(DMA0);

    // Initialize SPI peripheral
    SPI_MasterGetDefaultConfig(&masterConfig);
    masterConfig.sselNum = SPI_SSEL;
    SPI_MasterInit(SPI0, &masterConfig, srcClock_Hz);

    // Enable DMA channels connected to SPI0 Tx/SPI0 Rx request lines
    DMA_EnableChannel(SPI0, SPI_MASTER_TX_CHANNEL);
    DMA_EnableChannel(SPI0, SPI_MASTER_RX_CHANNEL);

    // Set DMA channels priority
    DMA_SetChannelPriority(SPI0, SPI_MASTER_TX_CHANNEL, kDMA_ChannelPriority3);
    DMA_SetChannelPriority(SPI0, SPI_MASTER_RX_CHANNEL, kDMA_ChannelPriority2);

    // Creates the DMA handle.
    DMA_CreateHandle(&masterTxHandle, SPI0, SPI_MASTER_TX_CHANNEL);
    DMA_CreateHandle(&masterRxHandle, SPI0, SPI_MASTER_RX_CHANNEL);

    // Create SPI DMA handle
    SPI_MasterTransferCreateHandleDMA(SPI0, spiHandle, SPI_UserCallback, NULL, &g_spiTxDmaHandle, &g_spiRxDmaHandle);

    // Prepares to send.
    xfer.txData = sendData;
    xfer.rxData = receiveBuff;
    xfer.dataSize = sizeof(sendData);

    // Sends out.
    SPI_MasterTransferDMA(SPI0, &spiHandle, &xfer);

    // Waits for send to complete.
    while (!isFinished)
    {
    }

    // ...
}

Modules
	SPI CMSIS driver
	SPI DMA Driver
	SPI FreeRTOS driver