Proteus中MSP430与SHT11的IIC通信问题

调了两天，MSP430始终接收不到数据，一直以为是代码的问题，今天无意中看到别人的一片文章，才发现问题出在上拉电阻上。DATA线的上拉电阻不能太大，10k不行，换成了1k就没问题了。mark一下，顺便感谢那位作者，附上他的链接：http://blog.sina.com.cn/s/blog_52f5ded30100bf68.html

附上MSP430代码：

在main里调用：

s_connectionreset();

s_write_status();

for(;;)

{

  s_read_temp_and_humi();//读取温度、湿度

}

sht11.h：

enum {TEMP,HUMI};

#define S_DATA_OUT (P6DIR |= BIT3) //P6.5 OUT

#define S_DATA_IN (P6DIR &=~BIT3) //P6.5 IN

#define S_DATA (P6IN & BIT3) //P6.5 DATA

#define S_DATA_LOW (P6OUT &=~BIT3)

#define S_DATA_HIGH (P6OUT |= BIT3)

#define S_SCK_OUT (P6DIR |= BIT4)

#define S_SCK_LOW (P6OUT &=~BIT4)

#define S_SCK_HIGH (P6OUT |= BIT4)

#define noACK 0

#define ACK 1

//adr command r/w

#define MEASURE_TEMP 0x03 //000 0001 1

#define MEASURE_HUMI 0x05 //000 0010 1

#define MEASURE_STATUS 0x06 //000 0011 0

void delay(unsigned int k);

void s_transstart(void);

void s_connectionreset(void);

unsigned char s_write_byte(unsigned char value);

unsigned char s_read_byte(unsigned char ack);

void s_calc_sth11(void);

unsigned char s_measure(unsigned int *p_value, unsigned char mode);

void s_write_status();

void s_read_temp_and_humi(void);

unsigned int temperature,humidity;

float f_temperature,f_humidity;

unsigned char s_read_data(unsigned int *p_value);

unsigned char s_measure_cmd(unsigned char mode);

unsigned char s_error=0;

extern float humi;

/******************************************************************************/

/* Temperature and humidity sensor function start */

/******************************************************************************/

// generates a tran××ission start 

// _____ ________

// DATA: |_______|

// ___ ___

// SCK : ___| |___| |______ 

// calculates temperature [懊] and humidity [%RH] 

// input : humi [Ticks] (12 bit) 

// temp [Ticks] (14 bit)

// output: humi [%RH]

// temp [懊]

void s_calc_sth11(void)

{ 

  float rh; // rh: Humidity

  float t; // t: Temperature

  float ttt;

  if(temperature>7000) 

  ttt=temperature-7000;

  else

  ttt=7000-temperature;

  t=temperature*0.01 - 39.64-0.00000002*ttt*ttt; //calc. temperature from ticks to [℃]

  rh=(0.0405-0.0000028*humidity)*humidity -4.0; //calc. humidity from ticks to [%RH]

  rh=(t-25)*(0.01+0.00008*humidity)+rh; //calc. temperature compensated humidity [%RH]

  f_temperature=t;

  temperature=t; //return temperature [℃]

  f_humidity=rh;

  humidity=rh; //return humidity[%RH]

  if((t-temperature)>=0.5)

  temperature+=1;

  if((rh-humidity)>=0.5)

  humidity+=1;

  if(humidity>100) humidity=100; //cut if the value is outside of 

  if(humidity<1) humidity=1; //the physical possi××e range

  humi=0.123;

}

void s_transstart(void)

{ 

  S_DATA_OUT;

  S_SCK_OUT;

  S_DATA_HIGH; //Initial state

  S_SCK_LOW;

  S_SCK_HIGH;

  S_DATA_LOW;

  S_SCK_LOW;

  S_SCK_HIGH; 

  S_DATA_HIGH;

  S_SCK_LOW; 

}

// communication reset: DATA-line=1 and at least 9 SCK cycles followed by transstart

// _____________________________________________________ ________

// DATA: |_______|

// _ _ _ _ _ _ _ _ _ ___ ___

// SCK : __| |__| |__| |__| |__| |__| |__| |__| |__| |______| |___| |______

void s_connectionreset(void)

{ 

  unsigned char i; 

  S_DATA_OUT;

  S_SCK_OUT;

  S_DATA_HIGH; //Initial state

  S_SCK_LOW; 

  for(i=0;i<9;i++) //9 SCK cycles

  { 

    S_SCK_HIGH;

    //_nop();

    S_SCK_LOW;

  }

  s_transstart(); //tran××ission start

}

// writes a byte on the Sensibus and checks the acknowledge 

unsigned char s_write_byte(unsigned char value)

{ 

  unsigned char i,error=0; 

  S_DATA_OUT;

  for (i=0x80;i>0;i/=2) //shift bit for masking

  { 

    if (i & value) S_DATA_HIGH; //masking value with i , write to SENSI-BUS

    else S_DATA_LOW; 

    S_SCK_HIGH; //clk for SENSI-BUS

    S_SCK_LOW;

  }

  S_DATA_IN; 

  S_SCK_HIGH; //clk #9 for ack 

  error=S_DATA; //check ack (DATA will be pulled down by SHT11)

  S_SCK_LOW; 

  S_DATA_OUT; //release DATA-line

  return error; //error=1 in case of no acknowledge

}

// reads a byte form the Sensibus and gives an acknowledge in case of "ack=1" 

unsigned char s_read_byte(unsigned char ack)

{ 

  unsigned char i,val=0;

  S_DATA_IN;

  for (i=0x80;i>0;i/=2) //shift bit for masking

  { 

    S_SCK_HIGH; //clk for SENSI-BUS

    if (S_DATA) val=(val | i); //read bit 

    S_SCK_LOW; 

  }

  S_DATA_OUT;

  if(ack)

  S_DATA_LOW;

  else

  S_DATA_HIGH; //in case of "ack==1" pull down DATA-Line

  S_SCK_HIGH; //clk #9 for ack

  S_SCK_LOW; //release DATA-line

  return val;

} 

/*Write status register:12bit humi,14bit temp*/

void s_write_status(void)

{

  s_connectionreset();

  s_write_byte(MEASURE_STATUS);

  s_write_byte(0x00); 

}

// makes a measurement (humidity/temperature)

unsigned char s_measure(unsigned int *p_value,unsigned char mode)

{ 

  unsigned char error=0;

  unsigned int i;

  s_transstart(); //tran××ission start

  if(mode==TEMP) //send command to sensor

  error+=s_write_byte(MEASURE_TEMP);

  else

  error+=s_write_byte(MEASURE_HUMI);

  S_DATA_IN;

  for (i=0;i<65535;i++) 

    if(S_DATA==0) break; //wait until sensor has finished the measurement

  if(S_DATA) error+=1; // or timeout (~1 sec.) is reached

  *p_value =s_read_byte(ACK); //read the first byte (MSB)

  *p_value = (*p_value)<<8;

  (*p_value) +=s_read_byte(noACK); //read the second byte (LSB)

  return error;

}

/***mode:TEMP,HUMI***/

unsigned char s_measure_cmd(unsigned char mode)

{

  unsigned char error=0;

  s_transstart();

  if(mode==TEMP) //send command to sensor

  error+=s_write_byte(MEASURE_TEMP);

  else

  error+=s_write_byte(MEASURE_HUMI);

  S_DATA_IN;

  return error;

}

unsigned char s_read_data(unsigned int *p_value)

{

  if(S_DATA)

  return 1;

  else

  {

    *p_value =s_read_byte(ACK); //read the first byte (MSB)

    *p_value = (*p_value)<<8;

    (*p_value) +=s_read_byte(noACK); //read the second byte (LSB)

    return 0;

  }

}

// measure humidity [%RH](8 bit) and temperature [℃](12 bit)

void s_read_temp_and_humi(void)

{

  unsigned char error=1;

  while(error)

  {

    error=0;

    error+=s_measure(&humidity,HUMI); //measure humidity

    error+=s_measure(&temperature,TEMP); //measure temperature

    if(error!=0) 

    s_connectionreset(); //in case of an error: connection reset

    else

    s_calc_sth11(); //calculate humidity, temperature

  }

}

/******************************************************************************/

/* Temperature and humidity sensor function END */

/******************************************************************************/

void delay(unsigned int k)

{

  unsigned int ktemp;

  for(ktemp=0;ktemp