Датчик за налягане bmp085 на Bosch

Това е програма за четене на данни от датчик за налягане bmp085 и изчисляване на реалните температура и атмосферно налягане използвайки целочислена аритметика. В случая се използва DSPIC33FJ256MC710 микроконтролер  на Microchip, но би трябвало да работи и с всеки друг. За извеждане на данните се използва двуредов дисплей.

#include "./dspic33.h"
#INCLUDE <math.h>

#use delay(clock=20000000)
//#use rs232(UART1,baud=19200,parity=N,bits=8,stream=uart1)
#use i2c(Master,Fast,sda=PIN_G3,scl=PIN_G2)

    
     #define LCD_RS_PIN      PIN_D1////
     #define LCD_RW_PIN      PIN_D2
     #define LCD_ENABLE_PIN  PIN_D3 ////
     #define LCD_DATA4       PIN_D12                                    ////
     #define LCD_DATA5       PIN_D13                                    ////
     #define LCD_DATA6       PIN_D4                                    ////
     #define LCD_DATA7       PIN_D5  

#include <LCD.C>
                                         
 int oss=0; //oversampling 0-low current 1-standart, 2,3- precision  
 signed int32 UT ;
 unsigned int32 UP;
 signed int16 AC1,AC2,AC3;
 unsigned int16 AC4,AC5,AC6;
 signed int16 B1,B2,MB,MC,MD;
 signed int32 X1,X2,B5,temperature,B6,X3,B3, pressure;
 unsigned int32 B4,B7;
 float altitude;
 
 signed int16 bmp085_read(int reg_address);
 void bmp085_write_control(int data);

void main()
{  
    lcd_init();
    
    lcd_putc("\fDesigned by\n");
    lcd_putc("Martin Nikiforov");
    delay_ms(1000);
    lcd_putc("\f");
    
    AC1=bmp085_read(0xAA);   // read parameters from bmp085's eeprom
    AC2=bmp085_read(0xAC);
    AC3=bmp085_read(0xAE);
    
    AC4=bmp085_read(0xB0);
    AC5=bmp085_read(0xB2);
    AC6=bmp085_read(0xB4);
    
    B1=bmp085_read(0xB6);
    B2=bmp085_read(0xB8);
    MB=bmp085_read(0xBA);
    MC=bmp085_read(0xBC);
    MD=bmp085_read(0xBE);

 oss=3;//0-low current for more accuracy 1,2,3
 while(true)
 {
   bmp085_write_control(0x2E);  //0x2E set to measure temperature   4,5ms                                                              
    delay_ms(5);
    UT=(unsigned int16)bmp085_read(0xF6); //read 0xF6 register temperature                             
        
    bmp085_write_control(0x34+(0x40*oss));  //0x34 - oss=0 set to measure pressure   4,5ms conv
                                            //oss=1 the value must be 0x74 oss =2 0xb4 , oss=3 0xF4
    delay_ms(7*(oss+1));
    
    UP=(unsigned int16)bmp085_read(0xF6);//pressure
    UP<<=8;
    UP=(UP+(((unsigned int16)bmp085_read(0xF8))>>8))>>(8-oss);//XLSB extra precision byte
    
    X1=((UT-AC6)*AC5)>>15;
    X2=(((signed int32)MC)<<11)/(X1+MD);
    B5=X1+X2;
    temperature=(B5+8)>>4;            
    
    B6=B5-4000;
    X1=(((signed int32)B2)*((B6*B6)/4096))/2048;
    X2=(((signed int32)AC2)*B6)/2048;
    X3=X1+X2;
    B3=((((((signed int32)AC1)*4)+X3)*((int)pow(2,oss)))+2)/4;
    X1=(((signed int32)AC3)*B6)/8192;
    X2=(((signed int32)B1)*((B6*B6)/4096))/65536;
    X3=((X1+X2)+2)/4;
    B4=(((unsigned int32)AC4)*(unsigned int32)(X3+32768))>>15;
    B7=(unsigned int32)(((unsigned int32)UP)-B3)*(50000>>oss);
    if(B7<0x80000000){pressure=(B7<<1)/B4;}
    else {pressure=(B7/B4)*2;}
    X1=(pressure>>8)*(pressure>>8);
    X1=(((unsigned int32)X1)*3038)/65536;                                         
    X2=(-7357*pressure)/65536;
    pressure=pressure+(X1+X2+3791)/16;
       
    altitude=  44330.0*(1.0-pow((pressure/102325.0),(1/5.255)));
    //calculate altitude 102325.0 must be 101325.0 but where i live give me negative altitude
    
                           
    printf(lcd_putc,"\aT=%4.1gC P=%5.1g\nAltitude%6.1g m\n",temperature/10.0,pressure/100.0,altitude);
  // screen refresh slowly when using \f
  delay_ms(200);
 }
    
}

signed int16 bmp085_read(int reg_address)
{
    int msb,lsb;
    int16 data=0;
    i2c_start();
    i2c_write(0b11101110);    // Device address
    i2c_write(reg_address);  // Data to device
    i2c_start();            // Restart
    i2c_write(0b11101111);     // to change data direction
    msb=i2c_read(1);        // Now read from slave
    lsb=i2c_read(0);
    i2c_stop();
    data=msb;
    data<<=8;
    data=data|lsb;
    return (data);
}
void bmp085_write_control(int data)
{

    i2c_start();
    i2c_write(0b11101110);//     // Device address
    i2c_write(0xF4);  //control reg address
    i2c_write(data);   //write the data                 
    i2c_stop();
    
}