temp.c

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/*
 *  Copyright (c) 2008  Swedish Institute of Computer Science
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions are met:
 *
 *  * Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *  * Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *  * Neither the name of the copyright holders nor the names of
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
/**
 * \file
 *
 * \brief
 *      Driver for the on board temperature sensor.
 *
 * \author
 *      Mike Vidales mavida404@gmail.com
 *
 */

#include "key.h"
#include "temp.h"
#include "lcd.h"

/**
 *  \addtogroup lcd
 *  \{
*/

/** Type used together with find_temp() to find temperature */
typedef enum {
    TEMP_ZERO_OFFSET_CELCIUS    = -15,
    TEMP_ZERO_OFFSET_FAHRENHEIT =   0
} temp_zero_offset_t;

#if defined( DOXYGEN )
static uint16_t temp_table_celcius[];
static uint16_t temp_table_fahrenheit[];
#else  /* !DOXYGEN */
/** Celcius temperatures (ADC-value) from -15 to 60 degrees */
static uint16_t temp_table_celcius[] PROGMEM = {
    923,917,911,904,898,891,883,876,868,860,851,843,834,825,815,
    806,796,786,775,765,754,743,732,720,709,697,685,673,661,649,
    636,624,611,599,586,574,562,549,537,524,512,500,488,476,464,
    452,440,429,418,406,396,385,374,364,354,344,334,324,315,306,
    297,288,279,271,263,255,247,240,233,225,219,212,205,199,193,
    187,
};

/** Fahrenheit temperatures (ADC-value) from 0 to 140 degrees */
static uint16_t temp_table_fahrenheit[] PROGMEM = {
    938, 935, 932, 929, 926, 923, 920, 916, 913, 909, 906, 902, 898,
    894, 891, 887, 882, 878, 874, 870, 865, 861, 856, 851, 847, 842,
    837, 832, 827, 822, 816, 811, 806, 800, 795, 789, 783, 778, 772,
    766, 760, 754, 748, 742, 735, 729, 723, 716, 710, 703, 697, 690,
    684, 677, 670, 663, 657, 650, 643, 636, 629, 622, 616, 609, 602,
    595, 588, 581, 574, 567, 560, 553, 546, 539, 533, 526, 519, 512,
    505, 498, 492, 485, 478, 472, 465, 459, 452, 446, 439, 433, 426,
    420, 414, 408, 402, 396, 390, 384, 378, 372, 366, 360, 355, 349,
    344, 338, 333, 327, 322, 317, 312, 307, 302, 297, 292, 287, 282,
    277, 273, 268, 264, 259, 255, 251, 246, 242, 238, 234, 230, 226,
    222, 219, 215, 211, 207, 204, 200, 197, 194, 190, 187,
};
#endif /* !DOXYGEN */

/** Flag indicating initialized or not */
bool temp_initialized = false;

/** \brief          Find array index corresponding to input ADC value
 *
 *                  Returned array index is actual temperature + zero offset. To
 *                  get actual temperature, the zero offset (\ref temp_zero_offset_t)
 *                  has to be subtracted.
 *
 * \param[in]           value                   Value to seracah for in table
 * \param[in]           array                   Pointer to array in which to look for ADC value
 * \param[in]           count                   Size of array
 *
 *
 * \return                              EOF on error
 */
static int find_temp(int16_t value, uint16_t* array, int count);

/*---------------------------------------------------------------------------*/

/**
 *   \brief This will initialize the digital IO and adc channel for temperture readings.
 *   Optionally enable adc channel 2 for measurement of EXT_SUPL_SIG.
 *
 *   \retval 0 Place holder for returning status.
*/
int
temp_init(void)
{
    /* Disable the Digital IO for the analog readings. */
    DIDR0 |= (1 << ADC4D);

    /* Temp sens power pin as output */
    TEMP_DDR |= (1 << TEMP_BIT_PWR);

    /* Power off temp sensor */
    TEMP_PORT &= ~(1 << TEMP_BIT_PWR);

    /* Temp sens input, no pullup */
    TEMP_DDR &= ~(1 << TEMP_BIT_IN);
    TEMP_PORT &= ~(1 << TEMP_BIT_IN);

#if MEASURE_ADC2
    DIDR0 |= (1 << ADC2D);
    TEMP_DDR &= ~(1 << 2);
    TEMP_PORT &= ~(1 << 2);
#endif   

    temp_initialized = true;

    return 0;
}

/*---------------------------------------------------------------------------*/

/**
 *   \brief This will disable temperature readings by reseting the initialed flag.
*/
void
temp_deinit(void)
{
    temp_initialized = false;
}

/*---------------------------------------------------------------------------*/

/**
 *   \brief This will turn on the adc channel for reading the temp sensor.
 *
 *   After the raw adc value is stored, it will be used to lookup a degree conversion
 *   based on the tables for F or C.
 *   Optionally, EXT_SUPL_SIG is also read on channel 2 and stored in the global
 *   ADC2_reading for subsequent transfer to the 1284p web server.
 *
 *   \param unit Used to determine what unit needs to be appended with the value.
 *
 *   \return EOF This is an uninitialized adc error.
 *   \retval temp The newly converted value in degrees F or C.
*/
#if MEASURE_ADC2
uint16_t ADC2_reading;
#endif

int16_t
temp_get(temp_unit_t unit)
{
    int16_t res;
    int16_t temp;

    /* Return if temp sensor driver not initialized */
    if (temp_initialized == false) {
        return EOF;
    }

    /* Power up sensor */
    TEMP_PORT |= (1 << TEMP_BIT_PWR);

    /* Init ADC and measure */
    adc_init(ADC_CHAN_ADC4, ADC_TRIG_FREE_RUN, ADC_REF_AVCC, ADC_PS_128);
    adc_conversion_start();
    while ((res = adc_result_get(ADC_ADJ_RIGHT)) == EOF ){
        ;
    }
    
#if MEASURE_ADC2
    /* Measure external voltage supply, routed to ADC2 through a 470K/100K divider*/
    /* AVCC is 3.3 volts if using external supply, else Vbat which will be lower */
    /* Convert result to millivolts assuming AVCC is 3.3 volts, on battery it will be lower! */
    adc_init(ADC_CHAN_ADC2, ADC_TRIG_FREE_RUN, ADC_REF_AVCC, ADC_PS_128);
    adc_conversion_start();
    while ((ADC2_reading = adc_result_get(ADC_ADJ_RIGHT)) == EOF ){
        ;
    }
    ADC2_reading = (ADC2_reading*((470+100)*3300UL))/(100*1024UL);
#endif
 
   adc_deinit();
    /* Re-init the adc for buttons. */
    key_init();

    /* Power down sensor */
    TEMP_PORT &= ~(1 << TEMP_BIT_PWR);

    /* Get corresponding temperature from table */
    if (unit == TEMP_UNIT_CELCIUS) {
        temp = find_temp(res, temp_table_celcius, sizeof(temp_table_celcius)/sizeof(int)) + TEMP_ZERO_OFFSET_CELCIUS;
    } else /*unit == TEMP_UNIT_FAHRENHEIT*/{
        temp = find_temp(res, temp_table_fahrenheit, sizeof(temp_table_fahrenheit)/sizeof(int)) + TEMP_ZERO_OFFSET_FAHRENHEIT;
    }

    return temp;
}

/*---------------------------------------------------------------------------*/

/**
 *   \brief Find array index corresponding to input ADC value
 *
 *   Returned array index is actual temperature + zero offset. To
 *   get actual temperature, the zero offset (\ref temp_zero_offset_t)
 *   has to be subtracted.
 *
 *   \param[in] value Value to search for in table
 *   \param[in] array Pointer to array in which to look for ADC value
 *   \param[in] count Size of array
 *
 *   \return         EOF on error
*/
static int
find_temp(int16_t value, uint16_t* array, int count)
{
    int i = 0;
    int table_val = 0;
    do{
        table_val = pgm_read_word(&array[i]);
        if (table_val < value) {
            return i;
        }
    } while(++i<count);
    return EOF;
}

/** \} */