使用GPIO模拟I2C通讯的代码

    以下代码是使用GPIO模拟IIC通讯的代码，时序由MCU产生，在CC2541上运行通过。

/*
 * file iic.h
 *
 */
#include "hal_types.h"

#ifndef __IIC_H__
#define __IIC_H__


#if 1 /* exchange SDA SCL */

#define SCL_SET() (I2CIO |= (1<<1))
#define SDA_SET() (I2CIO |= (1<<0))
#define SCL_CLR() (I2CIO &= ~(1<<1))
#define SDA_CLR() (I2CIO &= ~(1<<0))

#define SET_SDA_IN() (I2CWC &= ~(1<<0))
#define SET_SDA_OUT() (I2CWC |= 1)
#define GET_SDA() (I2CIO & 0x1)

#else

#define SCL_SET() (I2CIO |= (1<<0))
#define SDA_SET() (I2CIO |= (1<<1))
#define SCL_CLR() (I2CIO &= ~(1<<0))
#define SDA_CLR() (I2CIO &= ~(1<<1))

#define SET_SDA_IN() (I2CWC &= ~(1<<1))
#define SET_SDA_OUT() (I2CWC |= 1<<1)
#define GET_SDA() ((I2CIO>>1) & 0x1)

#endif


#define DEEP_OPTIMIZATION (0)

extern void iic_init(void);
extern void iic_release(void);
extern void iic_start(void);
extern void iic_stop(void);
extern uint8 iic_send_byte(uint8 data);
extern  uint8 iic_recv_byte_with_ack(void);
extern  uint8 iic_recv_byte_with_nak(void);

#endif

/*
 * file iic.c
 *
 */
#include "ioCC2541.h"
#include "hal_mcu.h"
#include "common_iic.h"

#define iic_nop() {\
                        asm("NOP");\
                    }

/*
 * Prototype : void iic_init(void)
 * Description : IIC init
 */
void iic_init(void)
{
  I2CCFG &= ~(1 << 6);

  SCL_SET();
  SDA_SET();

  I2CWC |= (1 << 7 | 0x3<<0);
}

/* release all iic pin to gpio */
void iic_release(void)
{
  SCL_CLR(); SET_SDA_IN();

  /* SWITCH TO IIC , AND DISABLE THE SDA ,SCL OUTPUT */
  I2CWC &= ~(0x1<<7);I2CWC |= (0x3<<0);
}


/*
 * Prototype : void iic_start(void)
 * Description : IIC init
 */
void inline iic_start(void)
{
#if DEEP_OPTIMIZATION == 1
    halIntState_t x;

    HAL_ENTER_CRITICAL_SECTION(x);
#endif

    SET_SDA_OUT();
    SDA_SET();
    iic_nop();
    SCL_SET();
    iic_nop();
    SDA_CLR();
    iic_nop();
    SCL_CLR();

#if DEEP_OPTIMIZATION == 1
    HAL_EXIT_CRITICAL_SECTION(x);
#endif
}

/*
 * Prototype :void iic_stop(void)
 * Description : IIC init
 */
void inline iic_stop(void)
{
#if DEEP_OPTIMIZATION == 1
    halIntState_t x;

    HAL_ENTER_CRITICAL_SECTION(x);
#endif

    SET_SDA_OUT();
    SDA_CLR();
    SCL_SET();
    iic_nop();
    SDA_SET();
    iic_nop();

#if DEEP_OPTIMIZATION == 1
    HAL_EXIT_CRITICAL_SECTION(x);
#endif
}

/* Prototype : uchar iic_send_byte(uchar sendDAT)
 *(Calls :
 *Parameters : uchar sendDAT---data to be send
 *Return Value : CY--slave ack (1---noack,0---ack)
 *Description : Send one byte to I2C
 */
uint8 iic_send_byte(uint8 data)
{
    uint8 i,revack = 1;

#if DEEP_OPTIMIZATION == 1
    halIntState_t x;

    HAL_ENTER_CRITICAL_SECTION(x);
#endif

    SCL_CLR();
    SET_SDA_OUT();

    for ( i = 0 ; i < 8; i++){
         SCL_CLR();
         iic_nop();

         if (data & 0x80){ // write data
               SDA_SET();
         }else {
               SDA_CLR();
         }

       data <<= 1;
       SCL_SET();
       iic_nop();
    }

    SCL_CLR();
    SDA_SET(); // release bus
    iic_nop();
    SET_SDA_IN();
    SCL_SET();
    revack = GET_SDA();

    SET_SDA_OUT();
    SCL_CLR();

#if DEEP_OPTIMIZATION == 1
    HAL_EXIT_CRITICAL_SECTION(x);
#endif
    return revack;
}

/* Prototype : uint8 iic_recv_byte(void)
 * Description : recv one byte from I2C
 */
uint8 iic_recv_byte_with_ack(void)
{
    uint8 value, i;

#if DEEP_OPTIMIZATION == 1
    halIntState_t x;

    HAL_ENTER_CRITICAL_SECTION(x);
#endif

    value = 0;

    SCL_CLR();
    SET_SDA_IN();
    for(i = 0; i < 8; i++){

        value <<= 1;
        SCL_SET();
        iic_nop();

        if(GET_SDA())
            value |= 1;

        SCL_CLR();
        iic_nop();

    }

    // send a ACK
    SET_SDA_OUT();
    SDA_CLR();
    iic_nop();
    SCL_SET();
    iic_nop();
    iic_nop();
    iic_nop();
    iic_nop();
    SCL_CLR();
    iic_nop();
    SDA_SET();
    iic_nop();

#if DEEP_OPTIMIZATION == 1
    HAL_EXIT_CRITICAL_SECTION(x);
#endif

    return value;
}

/* Prototype : uint8 iic_recv_byte_with_nak(void)
 * Description : recv one byte from I2C
 *
 * NOTE : IIC Master must send a 'NAK' to slave when last byte data was read,otherwise the
 * slave do not recognize the termination condition.
 */
uint8 iic_recv_byte_with_nak(void)
{
    uint8 value, i;

#if DEEP_OPTIMIZATION == 1
    halIntState_t x;

    HAL_ENTER_CRITICAL_SECTION(x);
#endif

    value = 0;

    SCL_CLR();
    SET_SDA_IN();
    for ( i = 0; i < 8; i++){

        value <<= 1;
        SCL_SET();
        iic_nop();

        if(GET_SDA())
            value |= 1;

        SCL_CLR();
        iic_nop();
    }

    // send a NAK
    SET_SDA_OUT();
    SDA_SET();
    iic_nop();
    SCL_SET();
    iic_nop();
    iic_nop();
    iic_nop();
    iic_nop();
    SCL_CLR();
    iic_nop();
#if DEEP_OPTIMIZATION == 1
    HAL_EXIT_CRITICAL_SECTION(x);
#endif

    return value;
}