I2C device read/write command program

//=========================
//Project:         I2C device read/write command program
//Author:         Leo.Tseng
//Date:            2011/09/30
//MCU:          W78E054D
//CRYSTAL: 25Mhz
//Description: Use uart for input/output, set boudrate=9600,
//                   input Hexadecimal data as your I2C device
//                   read/write address.
//=========================
#include  <reg52.h>
#include  <stdio.h>

//副程式宣告
void I2C_START(void);
void I2C_STOP(void);
void I2C_CLOCK(int t);
void I2C_write(unsigned char I2C_DATA,int i);
void delay(unsigned int d);
int I2C_ACK(void);
void TIMER1_initinal(int boudrate);
sbit SDA = P2^0; //SDA
sbit SCL = P2^1; //SCL
//======================================
//主程式開始
void main(void)
{
 unsigned char uart_data[2];
 unsigned int data_buf[2]={0,0};
 int i=0;
  unsigned char I2C_DATA=0xff;
  int device_ACK;
    
  TIMER1_initinal(9600);                    // 使用UART,baudrate=9600
  printf("\nInput Device Address : ");
  RI=0;
  TI=0;
  while(1)  
    {
     if(RI == 1)
      {                                                // 接收到uart字元
       RI = 0;                                      // 清除接收接收旗號,準備接收下一個字元
       uart_data[i] = SBUF;                // 讀取輸入字元
       SBUF = uart_data[i];                // 接收到的字元送回uart
       i++;
      }
     else TI = 0;                                 // 準備傳送下個接收字元
    
     if ((i==2)) break;
    }
   
  printf("\nEnd!!\n");
 
  for(i=0;i<2;i++)                                                           // 輸入字元限定判斷與轉換成16進位數值
   {                                                                                //
    if((uart_data[i]>='0')&&(uart_data[i]<='9'))                   // 限定0~9
     {                                                                              //
      data_buf[i]=uart_data[i]-0x30;                                //
     }                                                                             //
     else if((uart_data[i]>='A')&&(uart_data[i]<='F'))         // 限定A~F
           {                                                                       //
            data_buf[i]=uart_data[i]-0x37;                         //
           }                                                                      //
           else if((uart_data[i]>='a')&&(uart_data[i]<='f'))     // 限定a~f
                  {                                                                //
                   data_buf[i]=(uart_data[i]-0x57);               //
                  }                                                               //   
   }                                                          
                                                                 
 I2C_DATA=((data_buf[0]<<4)+(data_buf[1]&0x0f));   // 轉換輸入值

 I2C_START();                                                              // 開始I2C command
 
 delay(5);

 I2C_write(I2C_DATA,8);                                            // 寫入device address

 device_ACK=I2C_ACK();                                         // 取得device 狀態
 
 I2C_STOP();                                                              // 停止I2C command

 //printf("device_ACK=%d\n\n",device_ACK);

 if(device_ACK)                                                          // 判斷device是否有回應
    printf("Slave device is ACK!!\n\n");                         // 是, device ACK
  else printf("Slave device is no ACK!!\n\n") ;              // 否, device no ACK
 //printf("I2C stop!!\n");
}
//=======================================

//延時副程式
void delay(unsigned int d)
{  
 while (--d);
}

//I2C 開始副程式
//     ______
//SDA          \______
//     _________
//SCL                \_______
//               -| |-- START

void I2C_START(void)
{  
 if (SDA!=1) SDA=1;
 if (SCL!=1) SCL=1;
 delay(1);
 SDA = 0;
 delay(5);
 SCL = 0;
}

//I2C 停止副程式
//                            _______
//SDA _________/
//                     __________
//SCL ______/
//                          -| |-- STOP
void I2C_STOP(void)
{  
 if (SDA!=0) SDA=0;
 if (SCL!=0) SCL=0;
 delay(1);
 SCL = 1;
 delay(5);
 SDA = 1;
 delay(10);
}

//I2C clock 產生副程式
void I2C_CLOCK(int t)
{
 delay(t);
 SCL = 1;      //設定SCL為高位準
 delay(t);
 SCL = 0;      //設定SCL為高位準
}

//I2C write 副程式
void I2C_write(unsigned char I2C_DATA,int i)
{
 //bit data_bit;
 while(i--)
   {
    SDA=(I2C_DATA & 0x80)? 1 : 0;  //取出最高位元,並送至SDA
    delay(1);                                           //等待SDA穩定
    SCL = 1;
    delay(5);
    //I2C_CLOCK(5);
    I2C_DATA<<=1;                            //下個資料位元
    SCL = 0;
    //delay(1);
   }
}

//I2C ACK副程式
//                    ___________ NO ACK
//SDA _____/ \_________ ACK
//                     ____
//SCL ______/        \________
//                   -|  b9  |---- ACK bit
int I2C_ACK(void)
{  
 SDA=1;
 delay(2);
 SCL=1;
 if(SDA==0)                     // 判斷ack bit是否拉low
  {
   delay(6);
   SCL = 0;
   return 1;                    // 是
  }
  else
   {
    delay(6);
    SCL = 0;
    return 0;                   // 否
   }
 }

//UART副程式
void TIMER1_initinal(int boudrate)      
{
 PCON  = 0x00;                                   // PCON: if SMOD=1(b7), Baud Rate is Doubled                         
 SCON  = 0x52;                                          // SCON: mode 1, 8-bit UART, enable rcvr                   
 TMOD  = 0x20;                                          // TMOD: timer 1, mode 2, 8-bit reload         
 TH1   = 256-(25000000/372/boudrate);     // TH1:  reload value for baud @ 25MHz, TH=0xF9   
 TR1   = 1;                                                  // TR1:  timer 1 run                             
 //TI    = 1;                                                  // TI:   set TI to send first char of UART   
}