IIC 通用文件，文件是在NRF51xx 芯片基礎，keil 平臺開發測試通過，後期可以修改。

//Header files ...
#include "nrf_gpio.h"

typedef unsigned              char uint8;
typedef unsigned              int uint32;
//typedef   signed             char uint8;

#define I2C_FALSE            0     //returns 
#define I2C_TRUE             1     

#define
 
 I2C_DELAY_TM         1     //slot time (1us)

#define SDA                 15     //data
#define SCL                 16     //clock

// Output 0/1
#define SDA_OUT_0                            nrf_gpio_pin_write(SDA,0) 
#define SDA_OUT_1                            nrf_gpio_pin_write(SDA,1) 
#define SCL_OUT_0                            nrf_gpio_pin_write(SCL,0) 
#define
 
 SCL_OUT_1                            nrf_gpio_pin_write(SCL,1) 

//    Choose output/input 
#define SET_SDA_IN                   　　　　 ( I2C_SDA_Dir (1) ) 
#define SET_SDA_OUT                   　　　　( I2C_SDA_Dir (0) )
#define SET_SCL_IN                   　　　　 ( I2C_SCL_Dir (1) )
#define SET_SCL_OUT                   　　　　( I2C_SCL_Dir (0) )

//
 
 Reads lines
#define READ_SDA_IN                          nrf_gpio_pin_read(SDA)  
#define READ_SCL_IN                          nrf_gpio_pin_read(SCL) 

// 
#define NOP()                                 __nop()
#define I2C_Delay(x)                          nrf_delay_us(x) 

// Function declaration
void Delay1us(void);
void Delay5us(void);
void Delay10us(void);
void nrf_delay_ms(uint32 volatile number_of_ms);
void nrf_delay_us(uint32 volatile number_of_us);
void I2c_Stop(void);
void I2c_NoAck(void);
void I2c_Reset (void);
uint8 I2c_Start(void);
uint8 I2C_RcvByte(void);
void I2C_SendByte(uint8 c);
void I2C_SDA_Dir (uint8 dir);
void I2C_SCL_Dir (uint8 dir);


/**@brief Delay 5us
 */
void Delay1us(void)
{
    NOP();
        NOP();
        NOP();
        NOP();
}

/**@brief Delay 5us
 */
void Delay5us(void)
{
    Delay1us();
    Delay1us();
    Delay1us();
    Delay1us();
    Delay1us();
}

/**@brief Delay 10us
 */
void Delay10us(void)
{
    Delay5us();
    Delay5us();
}

/**@brief Delay(ms)  
 *
 * @param[in] number_of_ms 
 */
void nrf_delay_ms(uint32 volatile number_of_ms)
{
    number_of_ms = number_of_ms * 1000;
    while(number_of_ms != 0){
        number_of_ms--;
        Delay1us();
    }
}

/**@brief Delay(us)  
 *
 * @param[in] number_of_us 
 */
void nrf_delay_us(uint32 volatile number_of_us)
{
         while(number_of_us != 0){
        number_of_us--;
                Delay1us();
    }
}


/**@brief The data line outputs 0/1.
 *
 * @param[in] dir 
 */
void I2C_SDA_Dir (uint8 dir)
{
    if ( dir == 0 ) {
        nrf_gpio_cfg_output(SDA);
    }
    else {
        nrf_gpio_cfg_input(SDA,NRF_GPIO_PIN_PULLUP);
    }       
}

/**@brief The clock line outputs 0/1.
 *
 * @param[in] number_of_us 
 */
void I2C_SCL_Dir (uint8 dir)
{
       if ( dir == 0 ) {
           nrf_gpio_cfg_output(SCL);
    }
    else {
        nrf_gpio_cfg_input(SCL,NRF_GPIO_PIN_PULLUP);
    }
}    

/**@brief IIC communication to prepare.
 *
 * @param[in] i2c_master 
 */
uint8 I2c_Start(void)
{
      I2c_Reset();    
 
      SET_SCL_OUT;
      SET_SDA_OUT;  
      I2C_Delay(I2C_DELAY_TM);
    
      SDA_OUT_1;
      SCL_OUT_1;
      I2C_Delay(I2C_DELAY_TM);    
      if( !READ_SDA_IN ) {
            return I2C_FALSE; //BUSY
        }
      SDA_OUT_0;
      I2C_Delay(I2C_DELAY_TM);
      if( READ_SDA_IN ) {
            return I2C_FALSE; //ERROR
        }
      SDA_OUT_0;
      I2C_Delay(I2C_DELAY_TM);
      return I2C_TRUE;
}

/**@brief IIC stop the communication .
 *
 * @param[in] i2c_master 
 */
void I2c_Stop(void)
{
        SCL_OUT_0;
      I2C_Delay(I2C_DELAY_TM);
      SDA_OUT_0;
      I2C_Delay(I2C_DELAY_TM);
      SCL_OUT_1;
      I2C_Delay(I2C_DELAY_TM);
      SDA_OUT_1;
      I2C_Delay(I2C_DELAY_TM);
}
/**@brief reset  
 */
void I2c_Reset (void)
{
    if( READ_SDA_IN == 0  
        //|| READ_SCL_IN == 0 
        ) 
　　{    
      SET_SCL_OUT;
      SET_SDA_OUT;  
      I2C_Delay(I2C_DELAY_TM);
    
      SDA_OUT_1;
      SCL_OUT_1;
      I2C_Delay(I2C_DELAY_TM);
        
        I2C_SendByte(0xFF);
        I2c_NoAck();       
        I2c_Stop();    
    }
}
/**@brief Send the data ‘c‘ out,either as data or as an address.
 *
 * @param[in] C 
 */
void I2C_SendByte(uint8 c)
{
       uint8 i;
       i = 8;
  
        while(i--) 
        {
            SCL_OUT_0;    
            I2C_Delay(I2C_DELAY_TM); 
            if( c&0x80) {
                SDA_OUT_1;    
            }
            else {
                SDA_OUT_0;
            }                
            
            c<<=1;          
            I2C_Delay(I2C_DELAY_TM);
            SCL_OUT_1;
            I2C_Delay(I2C_DELAY_TM);
        }    
       SCL_OUT_0;    
}

/**@brief Reads a bytes of data and returns it.
 *
 * @param[out] retc 
 */
uint8 I2C_RcvByte(void)
{
       uint8 i = 8;
       uint8 retc = 0;
    
       SET_SDA_IN;
       SDA_OUT_1;
       while(i--) 
        {
           retc<<=1;
           SCL_OUT_0;
           I2C_Delay(I2C_DELAY_TM);
           SCL_OUT_1;
           I2C_Delay(I2C_DELAY_TM);
           if( READ_SDA_IN ) {
               retc |= 0x01;
           }
       }
       SCL_OUT_0;
       SET_SDA_OUT;
       
       return retc;    
}
/**@brief ACK response
 */
uint8 I2c_RecvACK(void)
{
        SCL_OUT_0;
      I2C_Delay(I2C_DELAY_TM);    
      SDA_OUT_1;
      SET_SDA_IN;
      I2C_Delay(I2C_DELAY_TM);
      SCL_OUT_1;
      I2C_Delay(I2C_DELAY_TM);
      if( READ_SDA_IN ) {
          SCL_OUT_0;
          SET_SDA_OUT;
          return I2C_FALSE;
      }
      else {
          SCL_OUT_0;
          SET_SDA_OUT;
          return I2C_TRUE;
      }
}
/**@brief Don‘t reply 
 */
void I2c_NoAck(void)
{
      SCL_OUT_0;
      I2C_Delay(I2C_DELAY_TM);    
      SDA_OUT_1;
      I2C_Delay(I2C_DELAY_TM);
      SCL_OUT_1;
      I2C_Delay(I2C_DELAY_TM);
      SCL_OUT_0;
      I2C_Delay(I2C_DELAY_TM);
}

《我的嵌入式開發》---- IIC 通信