File content as of revision 3:e2731f1e595b:

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

max31855::max31855(SPI& _spi, PinName ncs1, PinName ncs2) : _spi(_spi), _CS_1(ncs1), _CS_2(ncs2)
{

}

float max31855::read_temp(max31855::THERMOCOUPLES thermo)
{
    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;
    if (_pollTimer.read_ms() > 250) {
        //Set CS to initiate transfer and stop conversion
        select(thermo);
        //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)*0.0625;
        //Set CS to stop transfer and restart conversion
        deselect(thermo);
        if (CHECK_BIT(tempProbeLow, 0)) {
            //not connected error
            if(CHECK_BIT(tempChipLow, 0))return -2;
            //short to ground
            else if(CHECK_BIT(tempChipLow, 1))return -3;
            //short to VCC
            else if(CHECK_BIT(tempChipLow, 2))return -4;
            else return -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;
        }
    } else {
        return 8;
    }
}

void max31855::select(THERMOCOUPLES thermo)
{
    //Set CS low to start transmission (interrupts conversion)
    if(thermo == THERMO_1) _CS_1 = 0;
    else _CS_2 = 0;
}

void max31855::deselect(THERMOCOUPLES thermo)
{
    //Set CS high to stop transmission (restarts conversion)
    if(thermo == THERMO_1) _CS_1 = 1;
    else _CS_2 = 1;
    _pollTimer.reset();
}

void max31855::initialise(uint32_t interval)
{
    //Start the conversion timer
    _readInterval = interval;
    _pollTimer.start();
    _faultCode=0;
}

int max31855::ready()
{
    //Check to see if conversion is complete
    if(_pollTimer.read_ms() > _readInterval ) return 1;
    else return 0;
}