GPIO 模拟SPI驱动

最新推荐文章于 2024-10-24 23:49:16 发布

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最新推荐文章于 2024-10-24 23:49:16 发布

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分类专栏： linux 驱动开发文章标签： output input

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本文详细解析了使用GPIO模拟SPI驱动的关键点，并提供了源代码分析，重点在于每次传送8位数据时如何正确控制时钟信号的高低电平。通过实例展示了如何配置GPIO端口作为输出和输入，以及如何实现读写操作。

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GPIO模拟SPI驱动的关键点：每次传送8bit的时候都要先拉低时钟，本次传送结束后拉高时钟

下面是source code分析：

＃define APB_BASEADDR 0x10000000

#define GPIO_BASEADDR APB_BASEADDR + 0x070000

#define ROBO_SPI_BASEADDR(id) (GPIO_BASEADDR + (id)*0x2000)

#define ROBO_GPIO_0 0 //SDO

#define ROBO_GPIO_1 1 //SDI

#define ROBO_GPIO_2 2 //SCK

#define ROBO_GPIO_3 3 //CS

#define ROBO_SPI_SDO ROBO_SPI_BASEADDR(id) + 0X00 //输出

#define ROBO_SPI_SDO_CTRL ROBO_SPI_BASEADDR(id) + 0X04

#define ROBO_SPI_SDI ROBO_SPI_BASEADDR(id) + 0X10 //输入

#define ROBO_SPI_CS ROBO_SPI_BASEADDR(id) + 0X00

void robo_spi_write(u8 out_data)
{
   int i, rd_val, wr_val;

   //*(volatile u32 *)ROBO_SPI_CS &= ~(1<<ROBO_GPIO_3); //pull cs low

   for (i = 7; i >= 0; i--) {
    rd_val = *(volatile u32 *)ROBO_SPI_SDO;
    rd_val &= ~(1 << ROBO_GPIO_2); /* lower clock */
    wr_val = (((out_data >> i) & 1) << ROBO_GPIO_0);

    wr_val |= (rd_val & ~(1 << ROBO_GPIO_0));

  *(volatile u32 *)ROBO_SPI_SDO = wr_val;

    udelay (1000);

    wr_val |= (1 << ROBO_GPIO_2); /* high clock */
    *(volatile u32 *)ROBO_SPI_SDO = wr_val;

    udelay (1000);

   }

   //*(volatile u32 *)ROBO_SPI_CS |= 1<<ROBO_GPIO_3; //pull cs high

}

u8 robo_spi_read()
{
   int i, rd_val;
   u8 ret_val = 0;

//*(volatile u32 *)ROBO_SPI_CS &= ~(1<<ROBO_GPIO_3); //pull cs low

   /* Configure GPIO as input for data */
   rd_val = ((*(volatile u32 *)ROBO_SPI_SDI) & ~(1 << ROBO_GPIO_1));
   *(volatile u32 *)ROBO_SPI_SDI = rd_val;

   /* Configure GPIO as output for clock */
   rd_val = ((*(volatile u32 *)ROBO_SPI_SDO) | (1 << ROBO_GPIO_2));
   *(volatile u32 *)ROBO_SPI_SDI = rd_val;

   for (i = 7; i >= 0; i--) {
    rd_val = *(volatile u32 *)ROBO_SPI_SDO;
    rd_val &= ~(1 << ROBO_GPIO_2); /* lower clock */
    *(volatile u32 *)ROBO_SPI_SDO = rd_val;

    udelay (1000);

    rd_val = *(volatile u32 *)ROBO_SPI_SDO;
    rd_val |= (1 << ROBO_GPIO_2); /* high clock */
    *(volatile u32 *)ROBO_SPI_SDO = rd_val;

    udelay (1000);

    rd_val = *(volatile u32 *)ROBO_SPI_SDI;

    ret_val |= ((rd_val & (1 << ROBO_GPIO_1)) >> ROBO_GPIO_1) << i;
   }

   rd_val = *(volatile u32 *)ROBO_SPI_SDO;
   rd_val &= ~(1 << ROBO_GPIO_2); /* lower clock */
    *(volatile u32 *)ROBO_SPI_SDO = rd_val;

    //*(volatile u32 *)ROBO_SPI_CS |= 1<<ROBO_GPIO_3; //pull cs high

   return ret_val;
}

u8 robo_spi_read_write(u8 out_data)
{
   int i, rd_val,wr_val;
   u8 ret_val = 0;

    //*(volatile u32 *)ROBO_SPI_CS &= ~(1<<ROBO_GPIO_3); //pull cs low

   /* Configure GPIO as input for data */
   rd_val = ((*(volatile u32 *)ROBO_SPI_SDI) & ~(1 << ROBO_GPIO_1));
   *(volatile u32 *)ROBO_SPI_SDI = rd_val;

   /* Configure GPIO as output for clock */
   rd_val = ((*(volatile u32 *)ROBO_SPI_SDI) | (1 << ROBO_GPIO_2));
   *(volatile u32 *)ROBO_SPI_SDI = rd_val;
   for (i = 7; i >= 0; i--) {
        rd_val = *(volatile u32 *)ROBO_SPI_SDO;
        rd_val &= ~(1 << ROBO_GPIO_2); /* lower clock */
        wr_val = (((out_data >> i) & 1) << ROBO_GPIO_0);
        wr_val |= (rd_val & ~(1 << ROBO_GPIO_0));
      *(volatile u32 *)ROBO_SPI_SDO = wr_val;

udelay (1000);

        rd_val = *(volatile u32 *)ROBO_SPI_SDO;
        rd_val |= (1 << ROBO_GPIO_2); /* high clock */
        *(volatile u32 *)ROBO_SPI_SDO = rd_val;

        udelay (1000);
        rd_val = *(volatile u32 *)ROBO_SPI_SDI;
        ret_val |= ((rd_val & (1 << ROBO_GPIO_1)) >> ROBO_GPIO_1) << i;
   }
   rd_val = *(volatile u32 *)ROBO_SPI_SDO;
   rd_val &= ~(1 << ROBO_GPIO_2); /* lower clock */
    *(volatile u32 *)ROBO_SPI_SDO = rd_val;

    //*(volatile u32 *)ROBO_SPI_CS |= 1<<ROBO_GPIO_3; //pull cs high

   return ret_val;
}