[技术问答] 这个I2C的示例怎么有点看不懂？

/**************************************************************************//**

 * [url=home.php?mod=space&uid=288409]@file[/url]     main.c

 * [url=home.php?mod=space&uid=895143]@version[/url]  V3.00

 * $Revision: 7 $

 * $Date: 15/05/22 2:41p $

 * [url=home.php?mod=space&uid=247401]@brief[/url]    M051 Series I2C Driver Sample Code (Master)

 *

 * @note

 * Copyright (C) 2014 Nuvoton Technology Corp. All rights reserved.

 *

 ******************************************************************************/

#include <stdio.h>

#include "M051Series.h"



#define PLLCON_SETTING      SYSCLK_PLLCON_50MHz_XTAL

#define PLL_CLOCK           50000000



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

/* Global variables                                                                                        */

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

volatile uint8_t g_u8DeviceAddr;

volatile uint8_t g_au8MstTxData[3];

volatile uint8_t g_u8MstRxData;

volatile uint8_t g_u8MstDataLen;

volatile uint8_t g_u8MstEndFlag = 0;



typedef void (*I2C_FUNC)(uint32_t u32Status);



static volatile I2C_FUNC s_I2C0HandlerFn = NULL;

extern char GetChar(void);



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

/*  I2C0 IRQ Handler                                                                                       */

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

void I2C0_IRQHandler(void)

{

    uint32_t u32Status;



    u32Status = I2C_GET_STATUS(I2C0);



    if(I2C_GET_TIMEOUT_FLAG(I2C0))

    {

        /* Clear I2C0 Timeout Flag */

        I2C_ClearTimeoutFlag(I2C0);

    }

    else

    {

        if(s_I2C0HandlerFn != NULL)

            s_I2C0HandlerFn(u32Status);

    }

}



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

/*  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_STOP(I2C0);

        I2C_START(I2C0);

    }

    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_STOP(I2C0);

        I2C_START(I2C0);

    }

    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);

    }

}



void SYS_Init(void)

{

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

    /* Init System Clock                                                                                       */

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



    /* Enable Internal RC 22.1184MHz clock */

    CLK_EnableXtalRC(CLK_PWRCON_OSC22M_EN_Msk);



    /* Waiting for Internal RC clock ready */

    CLK_WaitClockReady(CLK_CLKSTATUS_OSC22M_STB_Msk);



    /* Switch HCLK clock source to Internal RC and HCLK source divide 1 */

    CLK_SetHCLK(CLK_CLKSEL0_HCLK_S_HIRC, CLK_CLKDIV_HCLK(1));



    /* Enable external XTAL 12MHz clock */

    CLK_EnableXtalRC(CLK_PWRCON_XTL12M_EN_Msk);



    /* Waiting for external XTAL clock ready */

    CLK_WaitClockReady(CLK_CLKSTATUS_XTL12M_STB_Msk);



    /* Set core clock as PLL_CLOCK from PLL */

    CLK_SetCoreClock(PLL_CLOCK);



    /* Enable UART & I2C0 module clock */

    CLK_EnableModuleClock(UART0_MODULE);

    CLK_EnableModuleClock(I2C0_MODULE);



    /* Select UART module clock source */

    CLK_SetModuleClock(UART0_MODULE, CLK_CLKSEL1_UART_S_HXT, CLK_CLKDIV_UART(1));



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

    /* Init I/O Multi-function                                                                                 */

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



    /* Set P3 multi-function pins for UART0 RXD and TXD */

    SYS->P3_MFP &= ~(SYS_MFP_P30_Msk | SYS_MFP_P31_Msk);

    SYS->P3_MFP |= (SYS_MFP_P30_RXD0 | SYS_MFP_P31_TXD0);



    /* 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);

}



void UART0_Init()

{

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

    /* Init UART                                                                                               */

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

    /* Reset IP */

    SYS_ResetModule(UART0_RST);



    /* Configure UART0 and set UART0 Baudrate */

    UART_Open(UART0, 115200);

}



void I2C0_Init(void)

{

    /* Open I2C module and set bus clock */

    I2C_Open(I2C0, 100000);



    /* Get I2C0 Bus Clock */

    printf("I2C clock %d Hz\n", I2C_GetBusClockFreq(I2C0));



    /* Set I2C 4 Slave Addresses */

    I2C_SetSlaveAddr(I2C0, 0, 0x15, 0);   /* Slave Address : 0x15 */

    I2C_SetSlaveAddr(I2C0, 1, 0x35, 0);   /* Slave Address : 0x35 */

    I2C_SetSlaveAddr(I2C0, 2, 0x55, 0);   /* Slave Address : 0x55 */

    I2C_SetSlaveAddr(I2C0, 3, 0x75, 0);   /* Slave Address : 0x75 */



    /* Enable I2C interrupt */

    I2C_EnableInt(I2C0);

    NVIC_EnableIRQ(I2C0_IRQn);

}



void I2C0_Close(void)

{

    /* Disable I2C0 interrupt and clear corresponding NVIC bit */

    I2C_DisableInt(I2C0);

    NVIC_DisableIRQ(I2C0_IRQn);



    /* Disable I2C0 and close I2C0 clock */

    I2C_Close(I2C0);

    CLK_DisableModuleClock(I2C0_MODULE);



}



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;

}

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

/*  Main Function                                                                                          */

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

int32_t main(void)

{

    /* Unlock protected registers */

    SYS_UnlockReg();



    /* Init System, IP clock and multi-function I/O */

    SYS_Init();



    /* Init UART0 for printf */

    UART0_Init();



    /* Lock protected registers */

    SYS_LockReg();



    /*

        This sample code sets I2C bus clock to 100kHz. Then, Master accesses Slave with Byte Write

        and Byte Read operations, and check if the read data is equal to the programmed data.

    */

    printf("\n");

    printf("+-------------------------------------------------------+\n");

    printf("| M05xx I2C Driver Sample Code(Master) for access Slave |\n");

    printf("|                                                       |\n");

    printf("| I2C Master (I2C0) <---> I2C Slave(I2C0)               |\n");

    printf("+-------------------------------------------------------+\n");



    printf("Configure I2C0 as a master.\n");

    printf("The I/O connection for I2C0:\n");

    printf("I2C0_SDA(P3.4), I2C0_SCL(P3.5)\n");



    /* Init I2C0 */

    I2C0_Init();



    printf("\n");

    printf("Check I2C Slave(I2C0) is running first!\n");

    printf("Press any key to continue.\n");

    GetChar();



    /* Access Slave with no address */

    printf("\n");

    printf(" == No Mask Address ==\n");

    I2C0_Read_Write_SLAVE(0x15);

    I2C0_Read_Write_SLAVE(0x35);

    I2C0_Read_Write_SLAVE(0x55);

    I2C0_Read_Write_SLAVE(0x75);

    printf("SLAVE Address test OK.\n");



    /* Access Slave with address mask */

    printf("\n");

    printf(" == Mask Address ==\n");

    I2C0_Read_Write_SLAVE(0x15 & ~0x01);

    I2C0_Read_Write_SLAVE(0x35 & ~0x04);

    I2C0_Read_Write_SLAVE(0x55 & ~0x01);

    I2C0_Read_Write_SLAVE(0x75 & ~0x04);

    printf("SLAVE Address Mask test OK.\n");



    s_I2C0HandlerFn = NULL;



    /* Close I2C0 */

    I2C0_Close();



    while(1);

}