在msp430上使用SHT70

属于msp430的串行接口传输数据的应用。SHTxx的串行接口与IIC不兼容，但其软件实现与IIC类似。

使用器件型号：msp430F169/msp430F149，SHT70@SENSIRION AG
典型应用电路：

代码：

#include <msp430x16x.h>
#include "intrinsics.h"
#include <math.h>     typedef unsigned int  uint;
typedef unsigned char uchar;char write_byte(uchar value);
char read_byte(uchar ack);
void transstart(void);
void connectionreset(void);
char softreset(void);
char read_statusreg(uchar *p_value, uchar *p_checksum);
char write_statusreg(uchar *p_value);
char measure(unsigned short int*p_value, uchar *p_checksum, uchar mode);
void calc_sth(unsigned short int t, unsigned short int rh, float *p_temperature, float *p_humidity);
float calc_dewpoint(float h,float t);
void sht10_init(void);
void CLK_Init();float humi_val_real=0.0;   float temp_val_real=0.0;float dew_point=0.0;#define noACK 0
#define ACK   1#define DATA_OUT  P5DIR |= BIT3
#define DATA_IN   P5DIR &=~BIT3
#define DATA_RIN  (P5IN & BIT3)#define DATA_H P5OUT |= BIT3 //DATA <---> P5.1
#define DATA_L P5OUT &=~ BIT3
#define SCK_H  P5OUT |= BIT4  //SCK  <---> P5.2
#define SCK_L  P5OUT &=~ BIT4#define REG_W 0x06  // 0000 0110
#define REG_R 0x07  // 0000 0111
#define TEMP  0x03  // 0000 0011
#define HUMI  0x05  // 0000 0101
#define RESET 0x1e  // 0001 1111#define CPU_F ((double)8000000)
#define delay_us(x) __delay_cycles((long)(CPU_F*(double)x/1000000.0))
#define delay_ms(x) __delay_cycles((long)(CPU_F*(double)x/1000.0))
void delay();char write_byte(uchar value)
//write a byte on the sensibus and checks the ackonwledge{uchar i,error = 0;DATA_OUT;for(i=0x80;i>0;i/=2){if(i&value){DATA_OUT;DATA_H;}else{DATA_OUT; DATA_L;}delay();SCK_H;
delay();//5msSCK_L;
delay();}DATA_IN; SCK_H;//delay_ms(800);error = DATA_RIN;SCK_L;return error;
}char read_byte(uchar ack)
// read a byte from sensibus and gives an ackowledge in case of 'ack =1'
{uchar i,val=0;DATA_IN;for (i=0x80;i>0;i/=2)             //shift bit for masking{
delay();SCK_H;                          //clk for SENSI-BUS
delay();if (DATA_RIN) val=(val | i);        //read bit  SCK_L;                      }DATA_OUT;if(ack) DATA_L;elseDATA_H;delay();SCK_H;                            //clk #9 for ackdelay();          //pulswith approx. 5 us SCK_L;                         delay();                        return val;}void transstart(void)
{DATA_OUT;DATA_H;SCK_L;
delay();SCK_H;
delay();DATA_L;
delay();SCK_L;
delay();SCK_H;
delay();DATA_H;
delay();SCK_L;
}void connectionreset(void)
{uchar i;DATA_OUT;DATA_H;SCK_L;for(i=0;i<9;i++){SCK_H;delay();SCK_L;delay();}transstart();
}char softreset(void)
{uchar error = 0;connectionreset();error += write_byte(RESET);return error;
}char read_statusreg(uchar *p_value, uchar *p_checksum)
//----------------------------------------------------------------------------------
// reads the status register with checksum (8-bit)
{ uchar error=0;transstart();                   //transmission starterror=write_byte(REG_R); //send command to sensor*p_value=read_byte(ACK);        //read status register (8-bit)*p_checksum=read_byte(noACK);   //read checksum (8-bit)  return error;                     //error=1 in case of no response form the sensor
}//----------------------------------------------------------------------------------
char write_statusreg(uchar *p_value)
//----------------------------------------------------------------------------------
// writes the status register with checksum (8-bit)
{ uchar error=0;transstart();                   //transmission starterror+=write_byte(REG_W);//send command to sensorerror+=write_byte(*p_value);    //send value of status registerreturn error;                     //error>=1 in case of no response form the sensor
}//----------------------------------------------------------------------------------
char measure(unsigned short int*p_value, uchar *p_checksum, uchar mode)
//----------------------------------------------------------------------------------
// makes a measurement (humidity/temperature) with checksum
{ uchar error=0;unsigned short int i;uchar value_H = 0,value_L = 0;transstart();                   //transmission startswitch(mode){                     //send command to sensorcase TEMP:error+=write_byte(TEMP); break;case HUMI:error+=write_byte(HUMI);break;default:break;  }DATA_IN;for (i=0;i<250;i++){
delay();
delay();
delay();
delay();if(DATA_RIN == 0) break;} //wait until sensor has finished the measurementif(DATA_RIN == 1) error+=1;                // or timeout (~2 sec.) is reachedvalue_H=read_byte(ACK);    //read the first byte (MSB)value_L =read_byte(ACK);    //read the second byte (LSB)*p_checksum =read_byte(noACK);  //read checksum*p_value = (value_H << 8) | value_L;return error;
}
void calc_sth(unsigned short int t, unsigned short int rh, float *p_temperature, float *p_humidity)
{const float d1 = -39.61;         //@3.3Vconst float d2 = +0.01;          //for 14 bit//for 12 bitconst float C1 = -2.0468;        const float C2 = +0.0367;const float C3 = -0.0000015955;//for 12 bitconst float T1 = +0.01;const float T2 = +0.00008;float RH_Lin; float RH_Ture;float temp_C;temp_C = d1 + d2 * t;                             RH_Lin = C1 + C2 * rh + C3 * rh * rh;            RH_Ture = (temp_C -25) * (T1 + T2 * rh) + RH_Lin; if(RH_Ture > 100)  RH_Ture = 100;if(RH_Ture < 0.1f)RH_Ture = 0.1;  *p_humidity = RH_Ture;*p_temperature = temp_C;
}float calc_dewpoint(float t,float h)
{ float dew_point;float m=17.62,Tn=243.12; //defaultif(-40<=t && t<0){m  = 22.46;Tn = 272.62;}dew_point = Tn*(log10(h)+m*t/(Tn+t))/(m-log10(h)-+m*t/(Tn+t));return dew_point;
}
void sht10_init(void)
{P5SEL = 0x00;// P5SEL |=BIT2;// P5SEL &=~ BIT1;// P5DIR &=~BIT1;//P5DIR |= BIT2;//DATA_OUT;P5DIR |= BIT3+BIT4;}void CLK_Init()
{unsigned int iq0;//BCSCTL1&=~0X00;                      //打开XT2振荡器BCSCTL1 &= ~XT2OFF;         //打开XT振荡器do{IFG1 &= ~OFIFG;                   // 清除振荡器失效标志for (iq0 = 0xFF; iq0 > 0; iq0--); // 延时，等待XT2起振}while ((IFG1 & OFIFG) != 0);        // 判断XT2是否起振//BCSCTL2 =SELM_2+SELS;               //选择MCLK、SMCLK为XT2BCSCTL2 |= SELM1+SELS;      //MCLK为8MHZ，SMCLK为8MHZ
}int main(void)
{ unsigned short int humi_val=0,temp_val=0;uchar error=0,checksum=0;WDTCTL=WDTPW+WDTHOLD;//int i;CLK_Init();sht10_init();connectionreset();while(1){ error=0;error+=measure(&temp_val,&checksum,TEMP);  //measure temperatureerror+=measure(&humi_val,&checksum,HUMI);  //measure humidityif(error!=0) connectionreset();                 else{                   calc_sth(temp_val,humi_val,&temp_val_real, &humi_val_real);            //calculate humidity, temperaturedew_point = calc_dewpoint(temp_val_real, humi_val_real); //printf("%2.1f℃  %2.1f%% %2.1f℃\r\n", temp_val_real, humi_val_real, dew_point);}//----------wait approx. 0.8s to avoid heating up SHTxx------------------------------      delay();delay();delay();}
}void delay(){for(int i=0;i<300;i++)for(int j=0;j<2;j++);}

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在msp430上使用SHT70

在msp430上使用SHT70

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