[参考译文] MSPM33C321A：SPI：TI 同步传输期间的额外位

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https://e2e.ti.com/support/microcontrollers/arm-based-microcontrollers-group/arm-based-microcontrollers/f/arm-based-microcontrollers-forum/1663844/mspm33c321a-spi-extra-bit-during-ti-synchonous-transfers

器件型号： MSPM33C321A

我使用 SPI 发送一个位流。我发现 Motorola SPI 模式在字节之间留下了间隙。 TI 同步模式没有、但它在第一个字节中放置了一个额外的位。

我对“spi_controller_multibyte_fifo_poll_LP_MSPM33C321A_nortos_ticlang“示例进行了轻微修改、以显示该问题。

#include "ti_msp_dl_config.h"

 

/*

 * Number of bytes for SPI packet size

 * The packet will be transmitted by the SPI controller.

 * This example uses FIFOs with polling, and the maximum FIFO size is 4.

 * Refer to interrupt examples to handle larger packets.

 */

#define SPI_PACKET_SIZE (2)

 

/* Data for SPI to transmit */

// packet size 4

//uint8_t gExpectedRxPacket[SPI_PACKET_SIZE] = {0x1, 0x2, 0x3, 0x4};

//uint8_t gTxPacket[SPI_PACKET_SIZE]         = {0xAA, 0x00, 0xFF, 0x55};

 

// packet size 2

uint8_t gExpectedRxPacket[SPI_PACKET_SIZE] = {0x1, 0x2};

uint8_t gTxPacket[SPI_PACKET_SIZE]         = {0xAA, 0x55};

 

volatile uint8_t gRxPacket[SPI_PACKET_SIZE];

#ifdef __SLATE_INTERNAL__

volatile bool gTransactionCompleted = false;

#endif

int main(void)

{

    SYSCFG_DL_init();

 

#ifdef __SLATE_INTERNAL__

    __BKPT(0);

#endif

    /* Fill TX FIFO with data and transmit to SPI Peripheral */

    DL_SPI_fillTXFIFO8(SPI_0_INST, &gTxPacket[0], SPI_PACKET_SIZE);

 

    /* Wait until all bytes have been transmitted and the TX FIFO is empty */

    while (DL_SPI_isBusy(SPI_0_INST))

        ;

 

    for (uint8_t i = 0; i < SPI_PACKET_SIZE; i++) {

        gRxPacket[i] = DL_SPI_receiveDataBlocking8(SPI_0_INST);

    }

#ifdef __SLATE_INTERNAL__

    gTransactionCompleted = true;

#endif

    /*

         * If this example is used with the spi_peripheral_multibyte_fifo_poll

         * example, the expected data to receive in gRxPacket is

         * {0x01, 0x02, 0x03, 0x04}.

         */

 

    /* If write and read were successful, toggle LED */

 

    while (!DL_SPI_isTXFIFOEmpty(SPI_0_INST))

        ;

 

    int allCorrect = 1;

    for (int i = 0; i < SPI_PACKET_SIZE; i++) {

        if (gExpectedRxPacket[i] != gRxPacket[i]) allCorrect = 0;

    }

 

    if (allCorrect == 1) {

        DL_GPIO_setPins(GPIO_LEDS_PORT, GPIO_LEDS_PASS_LED_PIN);

    }

    else{

        DL_GPIO_setPins(GPIO_LEDS_PORT, GPIO_LEDS_FAIL_LED_PIN);

    }

    __BKPT(0);

}

唯一真正的区别是更改发送的数据和更改 SPI 模式。

使用该示例的 Motorola 4 线 SPI 模式时、我得到：