MICRO2440 IIC_AT24C08学习

S3C2440A 的IIC 总线接口有4 种工作模式：

– 主机发送模式

– 主机接收模式

– 从机发送模式

– 从机接收模式

这里把S3C2440A单做主机，AT24C08单做从机，讲解主机发送模式，主机接收模式

I2C总线的数据传输协议如下：

（1）、主器件发出开始信号

（2）、主器件发出第一个字节，用来选通相应的从器件。其中前7位为地址码，第8位为方向位(R/W)。方向位为“0”表示发送，方向位为“1”表示接受。

（3）、从机产生应答信号，进入下一个传送周期，如果从器件没有给出应答信号，此时主器件产生一个结束信号使得传送结束，传送数据无效。

（4）、接下来主、从器件正式进行数据的传送，这时在I2C总线上每次传送的数据字节数不限，但每一个字节必须为8位（传送的时候先送高位，再送低位）。当一个字节传送完毕时，再发送一个应答位（第9位），如上一条所述，这样每次传送一个字节都需要9个时钟脉冲。

每一次传送之后都要进行应答，除非到了最后一个数据

当主器件传送一个字节后，在第9个SCL时钟内置高SDA线，而从器件的响应信号将SDA拉低，从而给出一个应答位。

当使用24WC08 时最多可连接2 个器件且仅使用地址管脚A2 A0 A1 管脚未用可以连接到

Vss（地） 或悬空如果只有一个24WC08 被总线寻址A2 管脚可悬空或连接到Vss

#include "2440addr.h"
#include "uart.h"
#include "def.h"
#include "IIC.h"


extern void Delay(int time);
//全局变量
static U8 _iicData[IICBUFSIZE];
static volatile int _iicDataCount;
static volatile int _iicStatus;
static volatile int _iicMode;
static int _iicPt;            //指针


void __irq IicInt(void)
{
    U32 iicSt,i;

    rSRCPND = BIT_IIC;          //Clear pending bit
    rINTPND = BIT_IIC;
    //iicSt   = rIICSTAT;

    //if(iicSt & 0x8){}           //When bus arbitration is failed.
    //if(iicSt & 0x4){}           //When a slave address is matched with IICADD
    //if(iicSt & 0x2){}           //When a slave address is 0000000b
    //if(iicSt & 0x1){}           //When ACK isn't received

    switch(_iicMode)
    {
       //case POLLACK:
        //   _iicStatus = iicSt;
         //  break;

       case RDDATA:
           if((_iicDataCount--)==0)
           {
               _iicData[_iicPt++] = rIICDS;

               rIICSTAT = 0x90;                 //Stop MasRx condition
               rIICCON  = 0xaf;                 //Resumes IIC operation.
               Delay(1);                        //Wait until stop condtion is in effect.
                                                //Too long time...
                                                //The pending bit will not be set after issuing stop condition.
               break;
           }
           _iicData[_iicPt++] = rIICDS;         //The last data has to be read with no ack.

           if((_iicDataCount)==0)
               rIICCON = 0x2f;                  //Resumes IIC operation with NOACK.
           else
               rIICCON = 0xaf;                  //Resumes IIC operation with ACK
               break;

        case WRDATA:
            if((_iicDataCount--)==0)
            {
                rIICSTAT = 0xd0;                //Stop MasTx condition
                rIICCON  = 0xaf;                //Resumes IIC operation.
                Delay(1);                       //Wait until stop condtion is in effect.
                       //The pending bit will not be set after issuing stop condition.
                break;
            }
            rIICDS = _iicData[_iicPt++];        //_iicData[0] has dummy.地址，不是我们要的数据
            for(i=0;i<10;i++);                  //for setup time until rising edge of IICSCL

            rIICCON = 0xaf;                     //resumes IIC operation.
            break;

        case SETRDADDR:
//          Uart_Printf("[ S%d ]",_iicDataCount);
            if((_iicDataCount--)==0)
                break;                          //IIC operation is stopped because of IICCON[4]
            rIICDS = _iicData[_iicPt++];        //扔到IICDATA数据线上，串行传输
            for(i=0;i<10;i++);                  //For setup time until rising edge of IICSCL
            rIICCON = 0xaf;                     //Resumes IIC operation.
            break;

        default:
            break;
    }
}





void Wr24C080(U32 slvAddr,U32 addr,U8 data)
{
    _iicMode      = WRDATA;
    _iicPt        = 0;
    _iicData[0]   = (U8)addr;
    _iicData[1]   = data;
    _iicDataCount = 2;

    rIICDS   = slvAddr;                 //0xa0
    rIICSTAT = 0xf0;                    //MasTx,Start
      //Clearing the pending bit isn't needed because the pending bit has been cleared.

    while(_iicDataCount!=-1);    //等待应答信号

    _iicMode = POLLACK;

    while(1)
    {
        rIICDS     = slvAddr;
        _iicStatus = 0x100;
        rIICSTAT   = 0xf0;              //MasTx,Start
        rIICCON    = 0xaf;              //Resumes IIC operation.

        //while(_iicStatus==0x100);//等待中断,这里无实质意义，
        //只是为了看状态寄存器的值改变否？用个1ms的延时代替也可
        Delay(1);

        if(!(_iicStatus&0x1))
            break;                      //When ACK is received
    }
    rIICSTAT = 0xd0;                    //Stop MasTx condition
    rIICCON  = 0xaf;                    //Resumes IIC operation.
    Delay(1);                           //Wait until stop condtion is in effect.
       //Write is completed.
}



void Rd24C080(U32 slvAddr,U32 addr,U8 *data)
{
    _iicMode      = SETRDADDR;
    _iicPt        = 0;
    _iicData[0]   = (U8)addr;
    _iicDataCount = 1;

    rIICDS   = slvAddr;
    rIICSTAT = 0xf0;                    //MasTx,Start
      //Clearing the pending bit isn't needed because the pending bit has been cleared.
    while(_iicDataCount!=-1);    //等待中断

    _iicMode      = RDDATA;
    _iicPt        = 0;
    _iicDataCount = 1;

    rIICDS        = slvAddr;
    rIICSTAT      = 0xb0;               //MasRx,Start
    rIICCON       = 0xaf;               //Resumes IIC operation.
    while(_iicDataCount!=-1);

    *data = _iicData[1];//数据总是放在这个元素里面
}





void Test_Iic(void)
{
    unsigned int i,j;
    static U8 data[256];

    Uart_Printf("\nIIC Test(Interrupt) using AT24C02\n");


    rGPEUP  |= 0xc000;                  //Pull-up disable
    rGPECON |= 0xa00000;                //GPE15:IICSDA , GPE14:IICSCL

    pISR_IIC = (unsigned)IicInt;    //中断处理函数的并联，要用到MMU，因为烧到SDRAM的话，中断向量不再0x00000000那里
    rINTMSK &= ~(BIT_IIC);        //开启中断

      //Enable ACK, Prescaler IICCLK=PCLK/16, Enable interrupt, Transmit clock value Tx clock=IICCLK/16
      // If PCLK 50.7MHz, IICCLK = 3.17MHz, Tx Clock = 0.198MHz
    rIICCON = (1<<7) | (0<<6) | (1<<5) | (0xf);

    //rIICADD  = 0x10;                    //2440 slave address = [7:1]，2440做从机的地址
    rIICSTAT = 0x10;                    //IIC bus data output enable(Rx/Tx)
    //rIICLC = (1<<2)|(1);          // Filter enable, 15 clocks SDA output delay       added by junon

    Uart_Printf("Write test data into AT24C08\n");

    for(i=0;i<256;i++)    //第一个参数：AT24C08地址，第二个参数：AT24C08内部地址，第三个参数，数据
        Wr24C080(0xa0,(U8)i,i);//0xa0,0xa1无所谓，因为2440有主从机收发4种模式

    for(i=0;i<256;i++)
        data[i] = 0;

    Uart_Printf("Read test data from AT24C08\n");

    for(i=0;i<256;i++)
        Rd24C080(0xa0,(U8)i,&(data[i])); //0xa0,0xa1无所谓，因为2440有主从机收发4种模式

        //Line changed 0 ~ f
    for(i=0;i<16;i++)
    {
        for(j=0;j<16;j++)
            Uart_Printf("%2x ",data[i*16+j]);
        Uart_Printf("\n");
    }
    rINTMSK |= BIT_IIC;   //关闭中断
}

说明：

1：注意那几个全局变量的值，很灵活，程序不好懂

2：发送，接受都是用到中断，尤其是应答信号，烧到SDRAM中的话，要在mian中初始化MMU，，因为烧到 SDRAM的话，中断向量已经改变了

3：操作时序按，2440芯片手册的主机收发模式操作，细细体会，出差的话很难调试的，尤其某些地方需要延时，试了好几个程序，都没成功，最终参看模板中的这个～_～