I2C的学习

只看该作者 · 2025-2-14 14:32

对于例子的学习，肯定要从程序开始看到最后，看和它相关的内容
比如I2C,在系统初始化函数内包含了，I2C模块的时钟使能和引脚映射

CLK_EnableModuleClock(I2C0_MODULE);

    /* Configure the SDA0 & SCL0 of I2C0 pins */

    SYS->P3_MFP &= ~(SYS_MFP_P34_Msk | SYS_MFP_P35_Msk);

    SYS->P3_MFP |= SYS_MFP_P34_SDA0 | SYS_MFP_P35_SCL0;

在I2C的初始化函数
设置了I2C的模块时钟设置，以及使能了相关中断功能

复制

<div><div>    /* Open I2C module and set bus clock */</div><div>    I2C_Open(I2C0, 100000);</div></div><div><div>    /* Enable I2C interrupt */</div><div>    I2C_EnableInt(I2C0);</div><div>    NVIC_EnableIRQ(I2C0_IRQn);</div></div>

只看该作者 · 2025-2-14 14:43

下面这个函数其实要控制的是几个全局变量

复制

int32_t I2C0_Read_Write_SLAVE(uint8_t slvaddr)

{

    uint32_t i;



    g_u8DeviceAddr = slvaddr;



    for(i = 0; i < 0x100; i++)

    {

        g_au8MstTxData[0] = (uint8_t)((i & 0xFF00) >> 8);

        g_au8MstTxData[1] = (uint8_t)(i & 0x00FF);

        g_au8MstTxData[2] = (uint8_t)(g_au8MstTxData[1] + 3);



        g_u8MstDataLen = 0;

        g_u8MstEndFlag = 0;



        /* I2C function to write data to slave */

        s_I2C0HandlerFn = (I2C_FUNC)I2C_MasterTx;



        /* I2C as master sends START signal */

        I2C_SET_CONTROL_REG(I2C0, I2C_I2CON_STA);



        /* Wait I2C Tx Finish */

        while(g_u8MstEndFlag == 0);

        g_u8MstEndFlag = 0;



        /* I2C function to read data from slave */

        s_I2C0HandlerFn = (I2C_FUNC)I2C_MasterRx;



        g_u8MstDataLen = 0;

        g_u8DeviceAddr = slvaddr;



        I2C_SET_CONTROL_REG(I2C0, I2C_I2CON_STA);



        /* Wait I2C Rx Finish */

        while(g_u8MstEndFlag == 0);



        /* Compare data */

        if(g_u8MstRxData != g_au8MstTxData[2])

        {

            printf("I2C Byte Write/Read Failed, Data 0x%x\n", g_u8MstRxData);

            return -1;

        }

    }

    printf("Master Access Slave (0x%X) Test OK\n", slvaddr);

    return 0;

}

实际应用中，肯定不是这么写，但是可以根据它的内容知道这些函数如何用
I2C_SET_CONTROL_REG(I2C0, I2C_I2CON_STA);
不管是发送完成还是接收完成都是通过中断标志g_u8MstEndFlag置位来实现。
发送和接收都在中断回调函数里执行。并根据状态字执行不同的动作

复制

/*---------------------------------------------------------------------------------------------------------*/

/*  I2C Rx Callback Function                                                                               */

/*---------------------------------------------------------------------------------------------------------*/

void I2C_MasterRx(uint32_t u32Status)

{

    if(u32Status == 0x08)                       /* START has been transmitted and prepare SLA+W */

    {

        I2C_SET_DATA(I2C0, (g_u8DeviceAddr << 1));    /* Write SLA+W to Register I2CDAT */

        I2C_SET_CONTROL_REG(I2C0, I2C_I2CON_SI);

    }

    else if(u32Status == 0x18)                  /* SLA+W has been transmitted and ACK has been received */

    {

        I2C_SET_DATA(I2C0, g_au8MstTxData[g_u8MstDataLen++]);

        I2C_SET_CONTROL_REG(I2C0, I2C_I2CON_SI);

    }

    else if(u32Status == 0x20)                  /* SLA+W has been transmitted and NACK has been received */

    {

        I2C_SET_CONTROL_REG(I2C0, I2C_I2CON_STA_STO_SI);

    }

    else if(u32Status == 0x28)                  /* DATA has been transmitted and ACK has been received */

    {

        if(g_u8MstDataLen != 2)

        {

            I2C_SET_DATA(I2C0, g_au8MstTxData[g_u8MstDataLen++]);

            I2C_SET_CONTROL_REG(I2C0, I2C_I2CON_SI);

        }

        else

        {

            I2C_SET_CONTROL_REG(I2C0, I2C_I2CON_STA_SI);

        }

    }

    else if(u32Status == 0x10)                  /* Repeat START has been transmitted and prepare SLA+R */

    {

        I2C_SET_DATA(I2C0, ((g_u8DeviceAddr << 1) | 0x01));   /* Write SLA+R to Register I2CDAT */

        I2C_SET_CONTROL_REG(I2C0, I2C_I2CON_SI);

    }

    else if(u32Status == 0x40)                  /* SLA+R has been transmitted and ACK has been received */

    {

        I2C_SET_CONTROL_REG(I2C0, I2C_I2CON_SI);

    }

    else if(u32Status == 0x58)                  /* DATA has been received and NACK has been returned */

    {

        g_u8MstRxData = (unsigned char) I2C_GET_DATA(I2C0);

        I2C_SET_CONTROL_REG(I2C0, I2C_I2CON_STO_SI);

        g_u8MstEndFlag = 1;

    }

    else

    {

        /* TO DO */

        printf("Status 0x%x is NOT processed\n", u32Status);

    }

}

/*---------------------------------------------------------------------------------------------------------*/

/*  I2C Tx Callback Function                                                                               */

/*---------------------------------------------------------------------------------------------------------*/

void I2C_MasterTx(uint32_t u32Status)

{

    if(u32Status == 0x08)                       /* START has been transmitted */

    {

        I2C_SET_DATA(I2C0, g_u8DeviceAddr << 1);    /* Write SLA+W to Register I2CDAT */

        I2C_SET_CONTROL_REG(I2C0, I2C_I2CON_SI);

    }

    else if(u32Status == 0x18)                  /* SLA+W has been transmitted and ACK has been received */

    {

        I2C_SET_DATA(I2C0, g_au8MstTxData[g_u8MstDataLen++]);

        I2C_SET_CONTROL_REG(I2C0, I2C_I2CON_SI);

    }

    else if(u32Status == 0x20)                  /* SLA+W has been transmitted and NACK has been received */

    {

        I2C_SET_CONTROL_REG(I2C0, I2C_I2CON_STA_STO_SI);

    }

    else if(u32Status == 0x28)                  /* DATA has been transmitted and ACK has been received */

    {

        if(g_u8MstDataLen != 3)

        {

            I2C_SET_DATA(I2C0, g_au8MstTxData[g_u8MstDataLen++]);

            I2C_SET_CONTROL_REG(I2C0, I2C_I2CON_SI);

        }

        else

        {

            I2C_SET_CONTROL_REG(I2C0, I2C_I2CON_STO_SI);

            g_u8MstEndFlag = 1;

        }

    }

    else

    {

        /* TO DO */

        printf("Status 0x%x is NOT processed\n", u32Status);

    }

}