void IIC_SDA_MODE(uint8_t SDA_Mode)
{
      GPIO_InitTypeDef  GPIO_InitStructure;
      GPIO_InitStructure.GPIO_Pin = IIC_SDA_PING;    
    if(SDA_Mode){
        GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;             
        GPIO_InitStructure.GPIO_Speed=GPIO_Speed_50MHz;
    }
    else 
    {
        GPIO_InitStructure.GPIO_Mode=GPIO_Mode_IN_FLOATING;
    }
    GPIO_Init(IIC_PORT, &GPIO_InitStructure);
}

void I2C_Start(void)
{
  SCL_H;
  delay_us(DELAYX_TIME);
  SDA_H;
  delay_us(DELAYX_TIME);
  SDA_L;
  delay_us(DELAYX_TIME);
  SCL_L;
  delay_us(DELAYX_TIME);
}

void I2C_Stop(void)
{
  SDA_L;
  delay_us(DELAYX_TIME);
  SCL_H;
  delay_us(DELAYX_TIME);
  SDA_H;
  delay_us(DELAYX_TIME);
}

void I2C_Ack(void)
{
  IIC_SDA_MODE(SDA_OUT);
  SCL_L;
  delay_us(DELAYX_TIME);
  SDA_L;
  delay_us(DELAYX_TIME);
  SCL_H;
  delay_us(DELAYX_TIME);
  SCL_L;
  delay_us(DELAYX_TIME);

}

void I2C_NoAck(void)
{
  IIC_SDA_MODE(SDA_OUT);
  SCL_L;
  delay_us(DELAYX_TIME);
  SDA_H;
  delay_us(DELAYX_TIME);
  SCL_H;
  delay_us(DELAYX_TIME);
  SCL_L;
  delay_us(DELAYX_TIME);

}


uint8_t I2C_WaitAck(uint16_t waitime)
{
  SCL_L;
  delay_us(DELAYX_TIME);
  SDA_H;
    IIC_SDA_MODE(SDA_IN);
  delay_us(DELAYX_TIME);
  SCL_H;
  while(waitime){
        if(SDA==0)break;
        delay_us(DELAYX_TIME);
        waitime--;
    }
    IIC_SDA_MODE(SDA_OUT);
    return waitime;
}

void I2C_SendByte(uint8_t data)
{
  uint8_t i;
  SCL_L;
    delay_us(DELAYX_TIME);
    for(i = 0;i < 8;i++)
    {
        if(data & (0x01 << (7 - i))) SDA_H;
     else SDA_L;
        delay_us(DELAYX_TIME);
        SCL_H;
        delay_us(DELAYX_TIME);
        SCL_L;

    }
}

uint8_t I2C_ReadByte(void)
{
  uint8_t i,data = 0;
  SCL_L;
  SDA_H;
    IIC_SDA_MODE(SDA_IN);
  for(i=0;i<8;i++)
  {  
    SCL_H;
    delay_us(DELAYX_TIME); 
    data <<= 1;
    if(SDA)
    {
      data |= 0x01;
    }
        // SCL_H;
    // delay_us(DELAYX_TIME);
    SCL_L;
    delay_us(DELAYX_TIME);
  }
  IIC_SDA_MODE(SDA_OUT);
  printf("data = %#x\n", data);
  return data;
}

void write_reg(uint8_t reg, uint8_t data)
{
  I2C_Start();
  I2C_SendByte(LIS2DH12_I2C_ADD_H << 1);
  I2C_WaitAck(250);
  I2C_SendByte(reg);
  I2C_WaitAck(250);
  I2C_SendByte(data);
  I2C_WaitAck(250);
  I2C_Stop();
}

uint8_t IIC_read(uint8_t slave_addr, uint8_t registerAddr,uint8_t *bufp,uint16_t len)
{
  I2C_Start();
  I2C_SendByte(slave_addr<<1);
  printf("slave_addr = %#x\n", slave_addr<<1);
  I2C_WaitAck(250);
//  if (len !=1)
//  {
//    I2C_SendByte(registerAddr + 0x80); 
//    I2C_WaitAck(250);
 // }
 // else  
        I2C_SendByte(registerAddr);
//    printf("registerAddr = %#x\n", registerAddr);
    I2C_WaitAck(250);
    I2C_Start();
    I2C_SendByte((slave_addr<<1)+1);
//    printf("slave_addr = %#x\n", (slave_addr<<1)+1);
    I2C_WaitAck(2);
  for(int i=0;i<len;i++){
    *bufp = I2C_ReadByte();
    printf("bufp = %d\n", *bufp);
    if(i==len-1){
      I2C_NoAck();
    }else{
      I2C_Ack();
    }
  }
  I2C_Stop();
  return bufp[0];
}

void GPIO_I2C_init(void){

  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB,ENABLE);

  GPIO_InitTypeDef  GPIO_InitStructure; 
  GPIO_InitStructure.GPIO_Pin = IIC_SCL_PING | IIC_SDA_PING;
  GPIO_InitStructure.GPIO_Mode=GPIO_Mode_Out_PP;
  GPIO_InitStructure.GPIO_Speed=GPIO_Speed_50MHz;

  GPIO_Init(IIC_PORT,&GPIO_InitStructure);
  GPIO_SetBits(IIC_PORT,IIC_SCL_PING);
  GPIO_SetBits(IIC_PORT,IIC_SDA_PING);
}

 uint8_t i = 0;
/* Main Example --------------------------------------------------------------*/
void lis2dh12_read_data_polling(void)
{

  /* Initialize mems driver interface */
    uint8_t i = 0;
      uint8_t data[1];
    uint8_t ID;
    while (1) {
//       for (i=0; i<6; i++){
//         lis2dh12_iic_read_byte(0x28 +i, data + i);       //获取X、y、z轴的数据
//      }
//      sample.x = LIS2DH12_FROM_FS_2g_HR_TO_mg(*(int16_t*)data); 
//      sample.y = LIS2DH12_FROM_FS_2g_HR_TO_mg(*(int16_t*)(data+2));
//      sample.z = LIS2DH12_FROM_FS_2g_HR_TO_mg(*(int16_t*)(data+4));

//      sample.new_angle_x = atan((short)sample.x/(short)sqrt(pow(sample.y, 2)+pow(sample.z, 2))) * DEGREE_CAL; // 计算X轴的倾角
//      sample.new_angle_y = atan((short)sample.y/(short)sqrt(pow(sample.x, 2)+pow(sample.z, 2))) * DEGREE_CAL; // 计算Y轴的倾角
//      sample.new_angle_z = atan((short)sample.z/(short)sqrt(pow(sample.x, 2)+pow(sample.y, 2))) * DEGREE_CAL; // 计算Z轴的倾角

//      if (sample.new_angle_z < 0)
//      {
//      sample.new_angle_x = 180-sample.new_angle_x;
//      sample.new_angle_y = 180-sample.new_angle_y;
//      }
//       printf("X轴倾角: %hd 度\n", sample.new_angle_x);
//       printf("Y轴倾角: %hd 度\n", sample.new_angle_y);
//       printf("Z轴倾角: %hd 度\n", sample.new_angle_z);

        for (i=0; i<1; i++){
         ID = lis2dh12_iic_read_byte(0x0F, data);       //获取ID
    }
             printf("id = %d\n", ID);
        delay_ms(60);   //6ms  

   }
 }

static int32_t lis2dh12_iic_write_byte( uint8_t reg,uint8_t data)//写一个字节
{
      write_reg( reg, data);  
        return 1;
}

static int32_t lis2dh12_iic_read_byte(uint8_t reg, uint8_t *data)//读一个字节
{
      IIC_read(LIS2DH12_I2C_ADD_H, reg, data,1); 
      return data[i];
}

所以问题是？

搞个逻辑分析仪看看时序波形。特别注意下发送的设备的7bit地址对不对