8051微控制器下的SHT11温湿度传感器I2C通信示例

/***********************************************************************************
Project:          SHTxx demo program (V2.1)
Filename:         SHTxx_Sample_Code.c    

Prozessor:        80C51 family
Compiler:         Keil Version 6.14

Autor:            MST
Copyrigth:        (c) Sensirion AG      
***********************************************************************************/

#include <AT89X51.h> //Microcontroller specific library, e.g. port definitions
#include <intrins.h> //Keil library (is used for _nop()_ operation)  
#include <math.h>    //Keil library  
#include <stdio.h>   //Keil library

typedef union 
{ unsigned int i;
  float f;
} value;

//----------------------------------------------------------------------------------
// modul-var
//----------------------------------------------------------------------------------
enum {TEMP,HUMI};

#define DATA    P1_1
#define SCK    P1_0

#define noACK 0

#define ACK   1
                            //adr  command  r/w
#define STATUS_REG_W 0x06   //000   0011    0
#define STATUS_REG_R 0x07   //000   0011    1
#define MEASURE_TEMP 0x03   //000   0001    1
#define MEASURE_HUMI 0x05   //000   0010    1
#define RESET        0x1e   //000   1111    0

//----------------------------------------------------------------------------------
char s_write_byte(unsigned char value)
//----------------------------------------------------------------------------------
// writes a byte on the Sensibus and checks the acknowledge 
{ 
  unsigned char i,error=0;  
  for (i=0x80;i>0;i/=2)             //shift bit for masking
  { if (i & value) DATA=1;          //masking value with i , write to SENSI-BUS
    else DATA=0;                        
    SCK=1;                          //clk for SENSI-BUS
    _nop_();_nop_();_nop_();        //pulswith approx. 5 us   
    SCK=0;
  }
  DATA=1;                           //release DATA-line
  SCK=1;                            //clk #9 for ack 
  error=DATA;                       //check ack (DATA will be pulled down by SHT11)
  SCK=0;        
  return error;                     //error=1 in case of no acknowledge
}

//----------------------------------------------------------------------------------
char s_read_byte(unsigned char ack)