本次测试使用STM32C031的I2C接口应用。首先初始化STM32C031的I2C接口，使用GPIO为PB8和PB9.

生成工程之后就可以使用I2C接口了。

温湿度SHTC3是一个arduino接口扩展板，可以直接插在开发板上。

下面是shtc3的驱动代码：

extern I2C_HandleTypeDef hi2c1;

uint8_t I2C_Write(uint8_t index,uint8_t dev_addr, uint16_t cmd,uint32_t len,uint8_t *str,uint32_t num)   
{
    HAL_StatusTypeDef status = HAL_OK;

    status = HAL_I2C_Mem_Write(&hi2c1, dev_addr<<1, cmd, I2C_MEMADD_SIZE_16BIT, str, num, 1000);

    return status;
}

uint8_t I2C_Read(uint8_t index,uint8_t dev_addr, uint16_t cmd,uint32_t len,uint8_t *str,uint32_t num)
{
    HAL_StatusTypeDef status = HAL_OK;

    status = HAL_I2C_Mem_Read(&hi2c1, dev_addr<<1, cmd, I2C_MEMADD_SIZE_16BIT, str, num, 1000);

    return status;
}

void shtc3_gpio_init(void)
{

}

void SHTC3_WriteCmd(uint16_t cmd)
{
    uint8_t cbuf[2];
    cbuf[0]=cmd>>8;
    cbuf[1]=cmd&0xff;
    I2C_Write(0,SHTC3_ADDRESS,cmd,2,cbuf,0);
}

void SHTC3_ReadData(uint16_t cmd,uint8_t *buff,uint32_t len)
{
    uint8_t cbuf[2];
    cbuf[0]=cmd>>8;
    cbuf[1]=cmd&0xff;
    I2C_Read(0,SHTC3_ADDRESS,cmd,2,buff,len);
}

int SHTC3_CalcTemperature(uint16_t rawValue)
{
  // calculate temperature
  // T = -45 + 175 * rawValue / 2^16
  return (((175*1 * rawValue)>>16) - 45*1);   //放大100倍
}

int SHTC3_CalcHumidity(uint16_t rawValue)
{
  // calculate relative humidity
  // RH = rawValue / 2^16 * 100
  return ((100 * 1 * rawValue)>>16);   //放大100倍
}

static uint8_t SHTC3_CheckCRC(uint8_t *buff, uint32_t nbyte)
{
    uint32_t i;            // byte counter  
    uint8_t  bit;          // bit mask
    uint8_t  crc = 0xFF;   // calculated checksum

    // calculates 8-Bit checksum with given polynomial
    for(i = 0; i < nbyte; i++) 
    {
        crc ^= (buff[i]);
        for(bit = 8; bit > 0; --bit)
        {
            if(crc & 0x80) {
                crc = (crc << 1) ^ SHTC3_CRC_POLYNOMIAL;
            } else {
                crc = (crc << 1);
            }
        }
    }
    return crc;
}

uint16_t SHTC3_Init(void)
{
    uint16_t shtc3_id;
    uint8_t buff[4]={0};

    shtc3_id = 0;
    shtc3_gpio_init();

    HAL_Delay(1);
    SHTC3_ReadData(SHTC3_REG_ID,buff,3);
    if(buff[2] != SHTC3_CheckCRC(buff,2))
    {
        return -1;
    }

    HAL_Delay(10);
    SHTC3_WriteCmd(SHTC3_REG_WAKEUP);
    shtc3_id = (buff[0]<<8)|buff[1];
    return shtc3_id;
}

uint8_t SHTC3_GetMode1_TempRH(int *temp, int *humi)
{
    uint8_t buff[8]={0};

    SHTC3_ReadData(SHTC3_REG_CELPM_TEMP_RH,buff,6);
    if((buff[2] != SHTC3_CheckCRC(buff,2))||(buff[5] != SHTC3_CheckCRC(&buff[3],2)))
    {
        return 1;
    }
    *temp = SHTC3_CalcTemperature((buff[0]<<8)|buff[1]);
    *humi = SHTC3_CalcHumidity((buff[3]<<8)|buff[4]);
    return 0;
}

使用串口shell命令来测试一下：

void shell_shtc3(char argc, char *argv)
{
    int temp,rh;
    printf("shtc3 id=0x%X:\r\n",temp = SHTC3_Init());
    if(temp != -1)
    {
        SHTC3_GetMode1_TempRH(&temp,&rh);
        printf("temp=%d,\t rh=%d \r\n",temp,rh);
    }
}
NR_SHELL_CMD_EXPORT(shtc3, shell_shtc3, "get shtc3 data.");

下面编译下载到开发板上看看效果。