File content as of revision 0:5530bf2d0e94:

#include "MAX31850.h"

Serial pc(USBTX, USBRX);

#define ONEWIRE_INPUT(pin)  pin->input()
#define ONEWIRE_OUTPUT(pin) pin->output()
#define ONEWIRE_INIT(pin)

LinkedList<node> MAX31850::probes;
 
 
MAX31850::MAX31850 (PinName data_pin, PinName power_pin, bool power_polarity) : _datapin(data_pin), _parasitepin(power_pin) {
    int byte_counter;
    _power_polarity = power_polarity;

    _power_mosfet = power_pin != NC;
    
    for(byte_counter=0;byte_counter<9;byte_counter++)
        scratchpad[byte_counter] = 0x00;
    
    ONEWIRE_INIT((&_datapin));

    if (!unassignedProbe(&_datapin, _ROM))
        error("No unassigned MAX31850 found!\n");
    else {
        _datapin.input();
        probes.append(this);
        _parasite_power = false; //only set up to use external power right now
    }
}

MAX31850::~MAX31850 (void) {
    node *tmp;
    for(int i=1; i<=probes.length(); i++)
    {
        tmp = probes.pop(i);
        if (tmp->data == this)
            probes.remove(i);
    }
}

 
bool MAX31850::onewire_reset(DigitalInOut *pin) {
// This will return false if no devices are present on the data bus
    bool presence=false;
    ONEWIRE_OUTPUT(pin);
    pin->write(0);          // bring low for 500 us
    wait_us(500);
    ONEWIRE_INPUT(pin);       // let the data line float high
    wait_us(90);            // wait 90us
    if (pin->read()==0) // see if any devices are pulling the data line low
        presence=true;
    wait_us(410);
    return presence;
}
 
void MAX31850::onewire_bit_out (DigitalInOut *pin, bool bit_data) {
    ONEWIRE_OUTPUT(pin);
    pin->write(0);
    wait_us(3);                 // DXP modified from 5
    if (bit_data) {
        pin->write(1); // bring data line high
        wait_us(55);
    } else {
        wait_us(55);            // keep data line low
        pin->write(1);
        wait_us(10);            // DXP added to allow bus to float high before next bit_out
    }
}
 
void MAX31850::onewire_byte_out(char data) { // output data character (least sig bit first).
    int n;
    for (n=0; n<8; n++) {
        onewire_bit_out(&this->_datapin, data & 0x01);
        data = data >> 1; // now the next bit is in the least sig bit position.
    }
}
 
bool MAX31850::onewire_bit_in(DigitalInOut *pin) {
    bool answer;
    ONEWIRE_OUTPUT(pin);
    pin->write(0);
    wait_us(3);                 // DXP modified from 5
    ONEWIRE_INPUT(pin);
    wait_us(10);                // DXP modified from 5
    answer = pin->read();
    wait_us(45);                // DXP modified from 50
    return answer;
}
 
char MAX31850::onewire_byte_in() { // read byte, least sig byte first
    char answer = 0x00;
    int i;
    for (i=0; i<8; i++) {
        answer = answer >> 1; // shift over to make room for the next bit
        if (onewire_bit_in(&this->_datapin))
            answer = answer | 0x80; // if the data port is high, make this bit a 1
    }
    return answer;
}

bool MAX31850::unassignedProbe(PinName pin) {
    DigitalInOut _pin(pin);
    ONEWIRE_INIT((&_pin));
    char ROM_address[8];
    return search_ROM_routine(&_pin, 0xF0, ROM_address);
}
 
bool MAX31850::unassignedProbe(DigitalInOut *pin, char *ROM_address) {
    return search_ROM_routine(pin, 0xF0, ROM_address);
}
 
bool MAX31850::search_ROM_routine(DigitalInOut *pin, char command, char *ROM_address) {
    bool DS1820_done_flag = false;
    int DS1820_last_discrepancy = 0;
    char DS1820_search_ROM[8] = {0, 0, 0, 0, 0, 0, 0, 0};
    
    int discrepancy_marker, ROM_bit_index;
    bool return_value, Bit_A, Bit_B;
    char byte_counter, bit_mask;
 
    return_value=false;
    while (!DS1820_done_flag) {
        if (!onewire_reset(pin)) {
            return false;
        } else {
            ROM_bit_index=1;
            discrepancy_marker=0;
            char command_shift = command;
            for (int n=0; n<8; n++) {           // Search ROM command
                onewire_bit_out(pin, command_shift & 0x01);
                command_shift = command_shift >> 1; // now the next bit is in the least sig bit position.
            } 
            byte_counter = 0;
            bit_mask = 0x01;
            while (ROM_bit_index<=64) {
                Bit_A = onewire_bit_in(pin);
                Bit_B = onewire_bit_in(pin);
                if (Bit_A & Bit_B) {
                    discrepancy_marker = 0; // data read error, this should never happen
                    ROM_bit_index = 0xFF;
                } else {
                    if (Bit_A | Bit_B) {
                        // Set ROM bit to Bit_A
                        if (Bit_A) {
                            DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] | bit_mask; // Set ROM bit to one
                        } else {
                            DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] & ~bit_mask; // Set ROM bit to zero
                        }
                    } else {
                        // both bits A and B are low, so there are two or more devices present
                        if ( ROM_bit_index == DS1820_last_discrepancy ) {
                            DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] | bit_mask; // Set ROM bit to one
                        } else {
                            if ( ROM_bit_index > DS1820_last_discrepancy ) {
                                DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] & ~bit_mask; // Set ROM bit to zero
                                discrepancy_marker = ROM_bit_index;
                            } else {
                                if (( DS1820_search_ROM[byte_counter] & bit_mask) == 0x00 )
                                    discrepancy_marker = ROM_bit_index;
                            }
                        }
                    }
                    onewire_bit_out (pin, DS1820_search_ROM[byte_counter] & bit_mask);
                    ROM_bit_index++;
                    if (bit_mask & 0x80) {
                        byte_counter++;
                        bit_mask = 0x01;
                    } else {
                        bit_mask = bit_mask << 1;
                    }
                }
            }
            DS1820_last_discrepancy = discrepancy_marker;
            if (ROM_bit_index != 0xFF) {
                int i = 1;
                node *list_container;
                while(1) {
                    list_container = probes.pop(i);
                    if (list_container == NULL) {                             //End of list, or empty list
                        if (ROM_checksum_error(DS1820_search_ROM)) {          // Check the CRC
                            return false;
                        }
                        for(byte_counter=0;byte_counter<8;byte_counter++)
                            ROM_address[byte_counter] = DS1820_search_ROM[byte_counter];
                        return true;
                    } else {                    //Otherwise, check if ROM is already known
                        bool equal = true;
                        MAX31850
                     *pointer = (MAX31850
                    *) list_container->data;
                        char *ROM_compare = pointer->_ROM;
                        
                        for(byte_counter=0;byte_counter<8;byte_counter++) {
                            if ( ROM_compare[byte_counter] != DS1820_search_ROM[byte_counter])
                                equal = false;
                        }
                        if (equal)
                            break;
                        else
                            i++;
                    }
                }                        
            }
        }
        if (DS1820_last_discrepancy == 0)
            DS1820_done_flag = true;
    }
    return return_value;
}
 
void MAX31850::match_ROM() {
// Used to select a specific device
    int i;
    onewire_reset(&this->_datapin);
    onewire_byte_out( 0x55);  //Match ROM command
    for (i=0;i<8;i++) {
        onewire_byte_out(_ROM[i]);
    }
}
 
void MAX31850::skip_ROM() {
    onewire_reset(&this->_datapin);
    onewire_byte_out(0xCC);   // Skip ROM command
}
 
bool MAX31850::ROM_checksum_error(char *_ROM_address) {
    char _CRC=0x00;
    int i;
    for(i=0;i<7;i++) // Only going to shift the lower 7 bytes
        _CRC = CRC_byte(_CRC, _ROM_address[i]);
    // After 7 bytes CRC should equal the 8th byte (ROM CRC)
    return (_CRC!=_ROM_address[7]); // will return true if there is a CRC checksum mis-match         
}
 
bool MAX31850::scratchpad_checksum_error() {
    char _CRC=0x00;
    int i;
    for(i=0;i<8;i++) // Only going to shift the lower 8 bytes
        _CRC = CRC_byte(_CRC, scratchpad[i]);
    // After 8 bytes CRC should equal the 9th byte (scratchpad CRC)
    return (_CRC!=scratchpad[8]); // will return true if there is a CRC checksum mis-match        
}
 
char MAX31850::CRC_byte (char _CRC, char byte ) {
    int j;
    for(j=0;j<8;j++) {
        if ((byte & 0x01 ) ^ (_CRC & 0x01)) {
            // DATA ^ LSB CRC = 1
            _CRC = _CRC>>1;
            // Set the MSB to 1
            _CRC = _CRC | 0x80;
            // Check bit 3
            if (_CRC & 0x04) {
                _CRC = _CRC & 0xFB; // Bit 3 is set, so clear it
            } else {
                _CRC = _CRC | 0x04; // Bit 3 is clear, so set it
            }
            // Check bit 4
            if (_CRC & 0x08) {
                _CRC = _CRC & 0xF7; // Bit 4 is set, so clear it
            } else {
                _CRC = _CRC | 0x08; // Bit 4 is clear, so set it
            }
        } else {
            // DATA ^ LSB CRC = 0
            _CRC = _CRC>>1;
            // clear MSB
            _CRC = _CRC & 0x7F;
            // No need to check bits, with DATA ^ LSB CRC = 0, they will remain unchanged
        }
        byte = byte>>1;
    }
return _CRC;
}
 
void MAX31850::readAll() {
    // Convert temperature into scratchpad for all devices at once
    int delay_time = 75; //default delay time

    skip_ROM(); //Skip ROM command, will convert for all devices
    
    onewire_byte_out( 0x44);  //perform temperature conversion
    
    wait_ms(delay_time);
}
 
void MAX31850::read_scratchpad() {
    // This will copy the MAX31850's 9 bytes of scratchpad data
    // into the objects scratchpad array. Functions that use
    // scratchpad values will automaticaly call this procedure.
    int i;
    match_ROM();             // Select this device
    onewire_byte_out( 0xBE);   //Read Scratchpad command
    for(i=0;i<9;i++) {
        scratchpad[i] = onewire_byte_in();
    }
}

 
float MAX31850::getTemp(int scale) {
    float answer;
    int reading;
    read_scratchpad();
    if (scratchpad_checksum_error()) {
        //indicate we got a CRC error
        answer = invalid_conversion;
        pc.printf("CRC Error\r\n");
    }
    else {
        reading = (scratchpad[1] << 8) + scratchpad[0]; //combine first two bytes of scratchpad 
        reading  = reading >> 2; //shift right two to drop unused bits
        if (reading & 0x2000) { //check MSB to determin sign 
            reading = 0-((reading ^ 0x3fff) + 1); //use 2's compliment to convert back to positive number and make it a signed int
        }
        answer = reading +0.0; //convert to floating point
        answer = answer / 4.0; //shift decimal place over two places

        //unit convertion 
        //checks for passed in value first and if there is none it sets the units baced on class units variable
        switch(scale) {
            case C:
                break;
            case K:
                answer = answer + 273.15f;
                break;
            case F:
                answer = answer * 1.8f + 32.0f;
                break;
            case R:
                answer = answer * 1.8f + 491.67f;
                break;
            default:
                switch(_units) {
                    case C:
                        break;
                    case K:
                        answer = answer + 273.15f;
                        break;
                    case F:
                        answer = answer * 1.8f + 32.0f;
                        break;
                    case R:
                        answer = answer * 1.8f + 491.67f;
                        break;
                }
        }
    }
    return answer;
}

// Contributed by John M. Larkin (jlarkin@whitworth.edu)
unsigned long long MAX31850::getId() {
// This will return the 64 bit address of the connected MAX31850
    unsigned long long myName = 0;
    for (int i = 0; i<8; i++) {
        myName = (myName<<8) | _ROM[i];
    }
    return myName;
}

void MAX31850::setUnits(int units) {
    _units = units;
}