[EVAL-WSN]传感器篇——SHT21湿温传感器

dvd1478

一、性能介绍

Sensirion SHT21 是I2C 湿度和温度传感器 +/-2% RH accuracy

物理量的转换公式

二、硬件电路

SCL和 SDA信号线相互平行并且非常接 近，有可能导致信号串扰和通讯失败。解决方法是在两个信号线之间放置 VDD和/或 GND，将信号线隔开，和使用屏蔽电缆

须在电源引脚（VDD，GND）之间加一个 100nF的去藕电容，用于滤波。此电容应尽量靠近传感器

三、I2C命令

有两个模式 hold master 与 no hold master

hold master 模式，SHT21 转到master 模式，对CLK 控制，直至转换结束，期间I2C不能用于其他的通信

no hold master模式 SHT21 没有对CLK 控制，期间MCU可以和其他的通信，在没有转换结束是SHT21不产生应答信号

STH21的device address 为0x40

#define SHT21_DEV_ADDR         0x40//Current Sensirion Device Addr =0x40

#define RH_MEAS_CONST                           (-6)

#define T_MEAS_CONST                            (-46.85)

#define RH_MEAS_MULT_CONST12                    0.03051 // (125/2^RES); RES=12-bit for RH

#define T_MEAS_MULT_CONST14                     0.01054 // (172.72/2^RES); RES=14-bit for Temp

#define SHT21_I2C_WRITE_ADDR                0x80// (SHT21_DEV_ADDR<<1)|0

#define SHT21_I2C_READ_ADDR                0x81// (SHT21_DEV_ADDR<<1)|1

#define SHT21_Delay                0x1F //0x1FFF  //how much?????????????

#define SHT21_TRIG_T_MEAS_HOLDMASTER0xE3

#define SHT21_TRIG_RH_MEAS_HOLDMASTER0xE5

#define SHT21_WRITE_USER_REGISTER        0xE6

#define SHT21_READ_USER_REGISTER        0xE7

#define SHT21_TRIG_T_MEAS_NO_HOLDMASTER0xF3//POLL MODE

#define SHT21_TRIG_RH_MEAS_NO_HOLDMASTER    0xF5//POLL MODE

#define SHT21_SOFT_RESET_REGISTER        0xFE

#define SHT21_RESOLUTION_RH12BIT_T14BIT     0x00   //12-bit RH & 14-bit Temperature (DEFAULT)

#define SHT21_RESOLUTION_RH8BIT_T12BIT      0x01   //8-bit RH & 12-bit Temperature

#define SHT21_RESOLUTION_RH10BIT_T13BIT     0x80   //10-bit RH & 13-bit Temperature

#define SHT21_RESOLUTION_RH11BIT_T11BIT     0x81   //12-bit RH & 14-bit Temperature

#define SHT21_END_OF_BATTERY_ON             0x40

ADSENSORAPP_RESULT_TYPE SHT21_Init()

{

    ADSENSORAPP_RESULT_TYPE status;

//status = adsAPI_I2C_Reg_Write_Byte(SHT21_DEV_ADDR, SHT21_SOFT_RESET_REGISTER,0x00);

//adsAPI_Delay(SHT21_Delay*1000);

    status = adsAPI_I2C_Reg_Write_Byte(SHT21_DEV_ADDR,SHT21_WRITE_USER_REGISTER,SHT21_RESOLUTION_RH12BIT_T14BIT);//设置分辨率

    adsAPI_Delay(SHT21_Delay);

return  status;

}

ADSENSORAPP_RESULT_TYPE Get_Temp_From_SHT21()

{

    uint16_t Data;

    ADSENSORAPP_RESULT_TYPE result;

    NVIC_DisableIRQ(WUT_IRQn);

    result = adsAPI_I2C_Reg_Read_Word(SHT21_DEV_ADDR, SHT21_TRIG_T_MEAS_HOLDMASTER, &Data, 1);

//result = adsAPI_I2C_Reg_Read_Word(SHT21_DEV_ADDR, SHT21_TRIG_T_MEAS_NO_HOLDMASTER, &Data, 1);

    NVIC_EnableIRQ(WUT_IRQn);

if(result == API_FAIL) {

        SensData.SHT21_T=0.00;

} else {

        Data = Data >> 2;

        SensData.SHT21_T = (float) (T_MEAS_CONST + (T_MEAS_MULT_CONST14 * Data)); //Temparature = (-46.85+176.72*St/2^RES)

}

return result;

}

ADSENSORAPP_RESULT_TYPE Get_RH_From_SHT21()

{

    uint16_t Data;

    ADSENSORAPP_RESULT_TYPE result;

    NVIC_DisableIRQ(WUT_IRQn);//避免中断的干扰

    result = adsAPI_I2C_Reg_Read_Word(SHT21_DEV_ADDR, SHT21_TRIG_RH_MEAS_HOLDMASTER, &Data, 1);

//result = adsAPI_I2C_Reg_Read_Word(SHT21_DEV_ADDR, SHT21_TRIG_RH_MEAS_NO_HOLDMASTER, &Data, 1);

    NVIC_EnableIRQ(WUT_IRQn);

if(result == API_FAIL) {

        SensData.SHT21_RH=0.00;

} else {

        Data = Data >> 4;

        SensData.SHT21_RH = (float) (RH_MEAS_CONST + (RH_MEAS_MULT_CONST12 * Data)); //Relative Humidity = (-6 + 125*RHval/2^RES)

}

return result;

}

suoma

和SHT11有什么区别？

shaoziyang

代码用帖子中的代码工具（就是两个尖括号那个）发，格式就不会乱。