普通GPIO模拟SPI通信协议(软件SPI)

在工作中偶尔会遇到SPI不够用的情况，而我们又要去使用SPI通信协议，此时就需要我们自己去模拟SPI通信协议。我们知道SPI通信协议有四种模式，它们分别如下所示：

下面是我基于ATSAM4SD16B芯片在Atmel Studio上用普通GPIO模拟的SPI通信协议的代码：

#include "ioport.h"
#include "pio.h"
#include "delay.h"
#include "SAM4S_FSA.h"
#include 

// Define 4 SPI pins
#define CS IOPORT_CREATE_PIN(PIOA, 8)
#define SCLK IOPORT_CREATE_PIN(PIOA, 7)
#define MOSI IOPORT_CREATE_PIN(PIOA, 23)
#define MISO IOPORT_CREATE_PIN(PIOA, 20)

#define SPIDelay delay_us(1)

// Define SPI communication mode
typedef enum SPIMode
{
    Mode_1,   /* Clock Polarity is 0 and Clock Phase is 0 */
    Mode_2,   /* Clock Polarity is 0 and Clock Phase is 1 */
    Mode_3,   /* Clock Polarity is 1 and Clock Phase is 0 */
    Mode_4,   /* Clock Polarity is 1 and Clock Phase is 1 */
}SPIMode;

// Define SPI type
typedef enum SPIType
{
    SPIMaster,
    SPISlave,
}SPIType;

// Define SPI attribute
typedef struct SpiStruct
{
    unsigned int ui_CS;
    unsigned int ui_SCLK;
    unsigned int ui_MOSI;
    unsigned int ui_MISO;
    SPIMode spiMode;
    SPIType spiType;
}Spi_t;

// Function prototypes
void v_SPIInitSimulate(Spi_t* p_Spi);
void v_CSIsEnableSimulate(Spi_t* p_Spi, int i_IsEnable);
void v_SPIWriteSimulate(Spi_t* p_Spi, unsigned char* puc_Data, int i_DataLength);
void v_SPIReadSimulate(Spi_t* p_Spi, unsigned char* puc_Data, int i_DataLength);

// Define SPI pins
Spi_t Spi_0 = 
{
    .ui_CS = CS,
    .ui_SCLK = SCLK,
    .ui_MOSI = MOSI,
    .ui_MISO = MISO,
    .spiMode = Mode_1,
    .spiType = SPIMaster,
};

/* Brief: SPI protocol initiate Input: p_Spi, which spi use Output: None Return: None Author: Andy Lai */
void v_SPIInitSimulate(Spi_t* p_Spi)
{
    assert(p_Spi != NULL);

    if(p_Spi->spiMode == SPIMaster)
    {
        ioport_set_pin_dir(p_Spi->ui_CS, IOPORT_DIR_OUTPUT);
        ioport_set_pin_dir(p_Spi->ui_SCLK, IOPORT_DIR_OUTPUT);
        ioport_set_pin_dir(p_Spi->ui_MOSI, IOPORT_DIR_OUTPUT);
        ioport_set_pin_dir(p_Spi->ui_MISO, IOPORT_DIR_INPUT);
    }
    else
    {
        ioport_set_pin_dir(p_Spi->ui_CS, IOPORT_DIR_INPUT);
        ioport_set_pin_dir(p_Spi->ui_SCLK, IOPORT_DIR_INPUT);
        ioport_set_pin_dir(p_Spi->ui_MOSI, IOPORT_DIR_INPUT);
        ioport_set_pin_dir(p_Spi->ui_MISO, IOPORT_DIR_OUTPUT);
    }

    pio_set_pin_high(p_Spi->ui_CS);
    switch(p_Spi->spiMode)
    {
    case Mode_1:
    case Mode_2:
        pio_set_pin_low(p_Spi->ui_SCLK);
        break;
    case Mode_3:
    case Mode_4:
        pio_set_pin_high(p_Spi->ui_SCLK);
        break;
    }
}

/* Brief: CS low level signal enable and high level signal disable Input: (1)p_Spi, which spi use (2)i_IsEnable, Chip select(Slave select) enable flag Output: None Return: None Author: Andy Lai */
void v_CSIsEnableSimulate(Spi_t* p_Spi, int i_IsEnable)
{
    assert(p_Spi != NULL);

    if(i_IsEnable)
    {
        pio_set_pin_low(p_Spi->ui_CS);
    }
    else
    {
        pio_set_pin_high(p_Spi->ui_CS);
    }
}

/* Brief: Use SPI to write a byte data Input: (1)p_Spi, which spi use (2)uc_Bt, write byte data Output: None Return: None Author: Andy Lai */
static void v_SPIWriteByte(Spi_t* p_Spi, unsigned char uc_Bt)
{
    int i = 0;

    assert(p_Spi != NULL);

    switch(p_Spi->spiMode)
    {
    case Mode_1: /* Clock Polarity is 0 and Clock Phase is 0 */
        pio_set_pin_low(p_Spi->ui_SCLK);
        for(i = 7; i >= 0; i--)
        {
            pio_set_pin_low(p_Spi->ui_SCLK);
            SPIDelay;
            pio_set_pin_high(p_Spi->ui_SCLK);
            if(uc_Bt & (1 << i))
            {
                pio_set_pin_high(p_Spi->ui_MOSI);
            }
            else
            {
                pio_set_pin_low(p_Spi->ui_MOSI);
            }
            SPIDelay;
        }
        pio_set_pin_low(p_Spi->ui_SCLK);
        break;

    case Mode_2: /* Clock Polarity is 0 and Clock Phase is 1 */
        pio_set_pin_low(p_Spi->ui_SCLK);
        for(i = 7; i >= 0; i--)
        {
            pio_set_pin_high(p_Spi->ui_SCLK);
            if(uc_Bt & (1 << i))
            {
                pio_set_pin_high(p_Spi->ui_MOSI);
            }
            else
            {
                pio_set_pin_low(p_Spi->ui_MOSI);
            }
            SPIDelay;
            pio_set_pin_low(p_Spi->ui_SCLK);
            SPIDelay;
        }
        pio_set_pin_low(p_Spi->ui_SCLK);
        break;

    case Mode_3: /* Clock Polarity is 1 and Clock Phase is 0 */
        pio_set_pin_high(p_Spi->ui_SCLK);
        for(i = 7; i >= 0; i--)
        {
            pio_set_pin_high(p_Spi->ui_SCLK);
            if(uc_Bt & (1 << i))
            {
                pio_set_pin_high(p_Spi->ui_MOSI);
            }
            else
            {
                pio_set_pin_low(p_Spi->ui_MOSI);
            }
            SPIDelay;
            pio_set_pin_low(p_Spi->ui_SCLK);
            SPIDelay;
        }
        pio_set_pin_high(p_Spi->ui_SCLK);
        break;

    case Mode_4: /* Clock Polarity is 1 and Clock Phase is 1 */
        pio_set_pin_high(p_Spi->ui_SCLK);
        for(i = 7; i >= 0; i--)
        {
            pio_set_pin_low(p_Spi->ui_SCLK);
            if(uc_Bt & (1 << i))
            {
                pio_set_pin_high(p_Spi->ui_MOSI);
            }
            else
            {
                pio_set_pin_low(p_Spi->ui_MOSI);
            }
            SPIDelay;
            pio_set_pin_high(p_Spi->ui_SCLK);
            SPIDelay;
        }
        pio_set_pin_high(p_Spi->ui_SCLK);
        break;

    default:
        break;
    }
}

/* Brief: Use SPI protocol to write data Input: (1)p_Spi, which spi use (2)puc_Data, write data string (3)i_DataLength, write data length Output: None Return: None Author: Andy Lai */
void v_SPIWriteSimulate(Spi_t* p_Spi, unsigned char* puc_Data, int i_DataLength)
{
    int i = 0;

    assert(p_Spi != NULL);
    assert(puc_Data != NULL);
    assert(i_DataLength > 0);

    v_CSIsEnableSimulate(p_Spi, 1);
    delay_us(8);

    // Write data
    for(i = 0; i < i_DataLength; i++)
    {
        v_SPIWriteByte(p_Spi, puc_Data[i]);
    }

    delay_us(8);
    v_CSIsEnableSimulate(p_Spi, 0);
}

/* Brief: Read a byte data from SPI Input: p_Spi, which spi use Output: None Return: Read data Author: Andy Lai */
static unsigned char uc_SPIReadByte(Spi_t* p_Spi)
{
    int i = 0;
    unsigned char uc_ReadData = 0;

    assert(p_Spi != NULL);

    switch(p_Spi->spiMode)
    {
    case Mode_1: /* Clock Polarity is 0 and Clock Phase is 0 */
        pio_set_pin_low(p_Spi->ui_SCLK);
        for(i = 0; i < 8; i++)
        {
            pio_set_pin_low(p_Spi->ui_SCLK);
            SPIDelay;
            pio_set_pin_high(p_Spi->ui_SCLK);
            uc_ReadData = uc_ReadData << 1;
            uc_ReadData |= pio_get_pin_value(p_Spi->ui_MISO);
            SPIDelay;
        }
        pio_set_pin_low(p_Spi->ui_SCLK);
        break;

    case Mode_2: /* Clock Polarity is 0 and Clock Phase is 1 */
        pio_set_pin_low(p_Spi->ui_SCLK);
        for(i = 0; i < 8; i++)
        {
            pio_set_pin_high(p_Spi->ui_SCLK);
            SPIDelay;
            pio_set_pin_low(p_Spi->ui_SCLK);
            uc_ReadData = uc_ReadData << 1;
            uc_ReadData |= pio_get_pin_value(p_Spi->ui_MISO);
            SPIDelay;
        }
        pio_set_pin_low(p_Spi->ui_SCLK);
        break;

    case Mode_3: /* Clock Polarity is 1 and Clock Phase is 0 */
        pio_set_pin_high(p_Spi->ui_SCLK);
        for(i = 0; i < 8; i++)
        {
            pio_set_pin_high(p_Spi->ui_SCLK);
            SPIDelay;
            pio_set_pin_low(p_Spi->ui_SCLK);
            uc_ReadData = uc_ReadData << 1;
            uc_ReadData |= pio_get_pin_value(p_Spi->ui_MISO);
            SPIDelay;
        }
        pio_set_pin_high(p_Spi->ui_SCLK);
        break;

    case Mode_4:  /* Clock Polarity is 1 and Clock Phase is 1 */
        pio_set_pin_high(p_Spi->ui_SCLK);
        for(i = 0; i < 8; i++)
        {
            pio_set_pin_low(p_Spi->ui_SCLK);
            SPIDelay;
            pio_set_pin_high(p_Spi->ui_SCLK);
            uc_ReadData = uc_ReadData << 1;
            uc_ReadData |= pio_get_pin_value(p_Spi->ui_MISO);
            SPIDelay;
        }
        pio_set_pin_high(p_Spi->ui_SCLK);
        break;

    default:
        break;
    }

    return uc_ReadData;
}

/* Brief: Use SPI to read data Input: (1)p_Spi, which SPI use; (2)i_DataLength, the length of data that need to read Output: puc_Data, need to get data Return: None Author: Andy Lai */
void v_SPIReadSimulate(Spi_t* p_Spi, unsigned char* puc_Data, int i_DataLength)
{
    int i = 0;

    assert(p_Spi != NULL);
    assert(i_DataLength > 0);

    v_CSIsEnableSimulate(p_Spi, 1);
    delay_us(8);

    // Read data
    for(i = 0; i < i_DataLength; i++)
    {
        puc_Data[i] = uc_SPIReadByte(p_Spi);
    }

    delay_us(8);
    v_CSIsEnableSimulate(p_Spi, 0);
}

参考博客：http://blog.csdn.net/yangzheng_yz/article/details/50470577