TemperatureSensor.cpp

/*
 * TemperatureSensor.cpp
 *
 */

#include "TemperatureSensor.h"

static OneWire ds(CFG_IO_TEMPERATURE_SENSOR); // DS18B20 Temperature chip i/o

/**
 * Constructor
 */
TemperatureSensor::TemperatureSensor(byte addr[])
{
    memcpy(address, addr, 8); // copy over the contents of the source array
    temperature = 0.0;

    if (address[0] == 0x10) {
        type = DS18S20;
    } else if (address[0] == 0x28) {
        type = DS18B20;
    } else if (address[0] == 0x22) {
        type = DS1822;
    } else {
        type = UNKNOWN;
    }
}

/**
 * Get the type of the device
 */
TemperatureSensor::DeviceType TemperatureSensor::getType()
{
    return type;
}

/**
 * Get the type of the device as string
 */
char *TemperatureSensor::getTypeStr()
{
    switch (type) {
    case TemperatureSensor::DS18S20:
        return "DS18S20";
        break;
    case TemperatureSensor::DS18B20:
        return "DS18B20";
        break;
    case TemperatureSensor::DS1822:
        return "DS1822";
        break;
    default:
        return "unknown";
        break;
    }
}

/**
 * Get the address of the device
 */
byte *TemperatureSensor::getAddress()
{
    return address;
}

/**
 * Set the resolution of the DS18B20 between 9 or 12 bits.
 */
void TemperatureSensor::setResolution(byte resolution)
{
    if (resolution > 12 || resolution < 9)
        return;
    if (type != DS18B20)
        return;

    // Get byte for desired resolution
    byte resolutionByte = 0x1F; // 9 bit
    if (resolution == 12) {
        resolutionByte = 0x7F;
    } else if (resolution == 11) {
        resolutionByte = 0x5F;
    } else if (resolution == 10) {
        resolutionByte = 0x3F;
    }

    // set configuration
    ds.reset();
    ds.select(address);
    ds.write(0x4E);			// write scratchpad
    ds.write(0);				// TL
    ds.write(0);				// TH
    ds.write(resolutionByte);	// configuration register
    ds.write(0x48);			// copy scratchpad
}

/**
 * Order all temperature sensors to prepare data.
 */
void TemperatureSensor::prepareData()
{
    ds.reset();
    ds.skip(); // skip ROM - send to all devices
    ds.write(0x44); // start conversion
}

/**
 * Retrieve prepared data from temperature sensors
 */
void TemperatureSensor::retrieveData()
{
    byte data[9];

    ds.reset();
    ds.select(address);
    ds.write(0xBE); // read scratchpad
    ds.read_bytes(data, 9); // 9 bytes are required

    temperature = (data[1] << 8) | data[0];

    if (type == DS18S20) {
        temperature = temperature << 3; // 9 bit resolution default
        if (data[7] == 0x10) { // "count remain" gives full 12 bit resolution
            temperature = (temperature & 0xFFF0) + 12 - data[6];
        }
    } else {
        byte cfg = (data[4] & 0x60);
        // at lower res, the low bits are undefined, so let's zero them
        if (cfg == 0x00)
            temperature = temperature & ~7; // 9 bit resolution, 93.75 ms
        else if (cfg == 0x20)
            temperature = temperature & ~3; // 10 bit res, 187.5 ms
        else if (cfg == 0x40)
            temperature = temperature & ~1; // 11 bit res, 375 ms
    }
}

/**
 * Return the measured temperature in degree celsius
 */
float TemperatureSensor::getTemperatureCelsius()
{
    return (float) temperature / 16.0;
}

/**
 * Return the measured temperature in degree fahrenheit
 */
float TemperatureSensor::getTemperatureFahrenheit()
{
    return (float) temperature / 16.0 * 1.8 + 32.0;
}

/**
 * A static wrapper for the OneWire::reset_search()
 */
void TemperatureSensor::resetSearch()
{
    ds.reset_search();
}

/**
 * A static function to search for more devices and instanciate an object
 * for each found device.
 */
TemperatureSensor *TemperatureSensor::search()
{
    byte addr[8];

    if (ds.search(addr)) {
        if (OneWire::crc8(addr, 7) != addr[7]) {
            SerialUSB.print("invalid CRC!\n");
            return NULL;
        }
        return new TemperatureSensor(addr);
    }

    return NULL;
}