File content as of revision 2:b978f1503c27:

#include <mbed.h>
#include "max31855.h"

max31855::max31855(SPI& _spi, void(*sel)(void), void(*usel)(void)) : spi(_spi) {
    selectfxn = sel;
    unselectfxn = usel;
    initialise(0);
}

float max31855::read_temp() {
    short value = 0;
    float temp = 0;
    
    //Variables to hold probe temperature
    uint8_t tempProbeHigh=0;
    uint8_t tempProbeLow=0;
    
    //Variables to hold chip temperature and device status
    uint8_t tempChipHigh=0;
    uint8_t tempChipLow=0;
    
    select();

    //Read in Probe tempeature
    tempProbeHigh = spi.write(0);
    tempProbeLow = spi.write(0);
    
    //Get the chip temperature and the fault data
    tempChipHigh = spi.write(0);
    tempChipLow = spi.write(0);
    
    //Set the chip temperature    
    chipTemp = (tempChipHigh<<4 | tempChipLow>>4)*0.25;
    
    //Set CS to stop transfer and restart conversion
    deselect(); 
    
    //Check for a fault (last bit of transfer is fault bit)
    if ((tempProbeLow & 1)==1){
        //Chip reports a fault, extract fault from Chip Temperature data
        int faultType = (tempChipLow & 7);
        
        faultCode=faultType;
        
        return 2000+faultType;
        /*if (faultType==1){
            //Open circuit (no TC)
            return 2000 + faultType;
        }else if (faultType==2){
            //Short to GND
            return 2000 + faultType;
        }else if (faultType==4){
            //Short to VCC               
            return 0.4;
        }else{
            return 0.5;
        }*/
    }else{
        //Integer value of temperature
        value = (tempProbeHigh<< 6 | tempProbeLow>>2);

        //Get actual temperature (last 2 bits of integer are decimal 0.5 and 0.25)
        temp = (value*0.25); // Multiply the value by 0.25 to get temp in C or
                         //  * (9.0/5.0)) + 32.0;   // Convert value to F (ensure proper floats!)
                         
        return temp;
    }
}

void max31855::select() {
    //Set CS low to start transmission (interrupts conversion)
    //ncs = 0;
    selectfxn();
}

void max31855::deselect() {
    //Set CS high to stop transmission (restarts conversion)
    //ncs = 1;
    unselectfxn();    
}

void max31855::initialise(int setType) {
    //Start the conversion timer    
    faultCode=0;
}