File content as of revision 1:326ce5e200fb:

#include "MPL115A1.h"

float get_a0(uint16_t a0);
float get_b1(uint16_t b1);
float get_c1(uint16_t c1);
float get_c12(uint16_t c12);
float getPressure();

MPL115A1::MPL115A1(SPI &spi, NRF52_DigitalOut &cs) : spi(spi), cs(cs) {}

float get_a0(uint16_t a0){
    float temp_a0;
    float temp_frac;
    int temp_a0_int;
    uint8_t negative_flag = 0;
    
    if(a0 & 0x8000){
        a0 ^= 0xFFFF;   // Transform from 2's complement
        a0 -= 1;
        negative_flag = 1;
    }
    
    temp_a0_int = a0 & 0x7FF8;
    temp_a0_int = temp_a0_int >> a0_frac_bits;
    
    temp_a0 = temp_a0_int * 1.0;    // Int part
    temp_frac = (1.0/(1<<3));
    temp_frac *= (a0 & a0_frac_mask);
    temp_a0 = temp_a0 + temp_frac;
    
    if(negative_flag) temp_a0 = -temp_a0;
    
    return temp_a0;
}

float get_b1(uint16_t b1){
    float temp_b1;
    float temp_frac;
    int temp_b1_int;
    uint8_t negative_flag = 0;
    
    if (b1 & 0x8000){
        b1 ^= 0xFFFF;
        b1 -= 1;
        negative_flag = 1;
    }
    
    temp_b1_int = b1 & 0x6000;
    temp_b1_int = temp_b1_int >> b1_frac_bits;
    
    temp_b1 = temp_b1_int * 1.0;
    temp_frac = (b1 & b1_frac_mask) * (1.0/(1<<b1_frac_bits));
    temp_b1 = temp_b1 + temp_frac;
    
    if(negative_flag) temp_b1 = -temp_b1;
    
    return temp_b1;
}

float get_b2(uint16_t b2){
    float temp_b2;
    float temp_frac;
    int temp_b2_int;
    uint8_t negative_flag = 0;
    
    if (b2 & 0x8000){
        b2 ^= 0xFFFF;
        b2 -= 1;
        negative_flag = 1;
    }
    
    temp_b2_int = b2 & 0x4000;
    temp_b2_int = temp_b2_int >> b2_frac_bits;
    
    temp_b2 = temp_b2_int * 1.0;
    temp_frac = (b2 & b2_frac_mask) * (1.0/(1<<b2_frac_bits));
    temp_b2 = temp_b2 + temp_frac;
    
    if(negative_flag) temp_b2 = -temp_b2;
    
    return temp_b2;
}


float get_c12(uint16_t c12){
    float temp_c12;
    float temp_frac;
    uint8_t negative_flag = 0;
    
    c12 = c12 >> 2;
    
    if (c12 & 0x2000){
        c12 ^= 0xFFFF;
        c12 -= 1;
        negative_flag = 1;
    }
    
    temp_c12 = 0.000000000;
    temp_frac = (c12 & c12_frac_mask) * (1.0/(1<<c12_frac_bits));
    temp_c12 = temp_c12 + temp_frac;
    
    if(negative_flag) temp_c12 = -temp_c12;
    
    return temp_c12;
}

float MPL115A1::getPressure(){
    float pcomp = 0x00;
    volatile float pressure;

    uint16_t a0 = 0;
    uint16_t b1 = 0;
    uint16_t b2 = 0;
    uint16_t c12 = 0;
    uint16_t padc = 0;
    uint16_t tadc = 0;

    float a0_f, b1_f, b2_f, c12_f;
    cs = 0;
    spi.write(0x88);        // MSB a0
    a0 = spi.write(0x00);   
    a0 = a0 << 8;
    wait_ms(1); 
    spi.write(0x8A);        // LSB a0
    a0 |= spi.write(0x00);
    wait_ms(1);
    
    spi.write(0x8C);        // MSB b1
    b1 = spi.write(0x00);   
    b1 = b1 << 8;
    wait_ms(1);
    spi.write(0x8E);        // LSB b1
    b1 |= spi.write(0x00);
    wait_ms(1);
    
    spi.write(0x90);        // MSB b2
    b2 = spi.write(0x00);   
    b2 = b2 << 8;
    wait_ms(1);
    spi.write(0x92);        // LSB b2
    b2 |= spi.write(0x00);
    wait_ms(1);
    
    spi.write(0x94);        // MSB c12
    c12 = spi.write(0x00);  
    c12 = c12 << 8;
    wait_ms(1);
    spi.write(0x96);        // LSB c12
    c12 |= spi.write(0x00);
    wait_ms(1);
    spi.write(0x00);
    cs = 1;
    
    cs = 0;
    spi.write(0x24);        // Start conversion
    spi.write(0x00);
    cs = 1;
    wait_ms(3);
    
    cs = 0;
    spi.write(0x80);
    padc = spi.write(0x00); // MSB Padc
    padc = padc << 8;
    spi.write(0x82);
    padc |= spi.write(0x00);    // LSB Padc
    padc = padc >> 6;
    
    spi.write(0x84);                
    tadc = spi.write(0x00); // MSB Padc
    tadc = tadc << 8;
    spi.write(0x86);
    tadc |= spi.write(0x00);    // LSB Padc
    tadc = tadc >> 6;
    
    spi.write(0x00);
    cs = 1;
    
    a0_f  = get_a0(a0);
    b1_f  = get_b1(b1);
    b2_f  = get_b2(b2);
    c12_f = get_c12(c12);
    
    /*            
    float c12x2 = c12_f * tadc;
    float a1_f = b1_f + c12x2;
    float a1x1 = a1_f * padc;
    float y1 = a0_f + a1x1;
    float a2x2 = b2_f * tadc;
    pcomp = y1 + a2x2;
    */

    pcomp = a0_f + (b1_f + c12_f * tadc) * padc + b2_f * tadc;
    pressure = pcomp * ((115-50)/(1023.0)) + 52;    // Was + 50
    pressure *= 10;     // Calculate in hPa
    return pressure;
}