adc.c

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/***************************************************************************//**
 * @file adc.c
 * @brief ADC functionality for reading the (battery) voltage and internal temperature.
 * @version 2.1
 * @author Brecht Van Eeckhoudt
 *
 * ******************************************************************************
 *
 * @section Versions
 *
 *   @li v1.0: Moved ADC functionality from `other.c` to this file.
 *   @li v1.1: Removed re-initialization dbprint messages.
 *   @li v1.2: Started using custom enum type and cleaned up some unnecessary statements after testing.
 *   @li v1.3: Changed error numbering.
 *   @li v1.4: Added timeout to `while` loop and changed types to `int32_t`.
 *   @li v1.5: Refined timout functionality.
 *   @li v2.0: Disabled peripheral clock before entering an `error` function, added
 *             functionality to exit methods after `error` call and updated version number.
 *   @li v2.1: Removed `static` before the local variables (not necessary).
 *
 * ******************************************************************************
 *
 * @section License
 *
 *   **Copyright (C) 2019 - Brecht Van Eeckhoudt**
 *
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the **GNU General Public License** as published by
 *   the Free Software Foundation, either **version 3** of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   *A copy of the GNU General Public License can be found in the `LICENSE`
 *   file along with this source code.*
 *
 *   @n
 *
 *   Some methods use code obtained from examples from [Silicon Labs' GitHub](https://github.com/SiliconLabs/peripheral_examples).
 *   These sections are licensed under the Silabs License Agreement. See the file
 *   "Silabs_License_Agreement.txt" for details. Before using this software for
 *   any purpose, you must agree to the terms of that agreement.
 *
 ******************************************************************************/


#include <stdint.h>        /* (u)intXX_t */
#include <stdbool.h>       /* "bool", "true", "false" */
#include "em_device.h"     /* Include necessary MCU-specific header file */
#include "em_cmu.h"        /* Clock management unit */
#include "em_adc.h"        /* Analog to Digital Converter */

#include "adc.h"           /* Corresponding header file */
#include "debug_dbprint.h" /* Enable or disable printing to UART for debugging */
#include "util.h"          /* Utility functionality */


/* Local definitions */
/** Enable (1) or disable (0) printing the timeout counter value using DBPRINT */
#define DBPRINT_TIMEOUT 0

/** Maximum value for the counter before exiting a `while` loop */
#define TIMEOUT_CONVERSION 50


/* Local variables */
volatile bool adcConversionComplete = false; /* Volatile because it's modified by an interrupt service routine */
ADC_Init_TypeDef       init       = ADC_INIT_DEFAULT;
ADC_InitSingle_TypeDef initSingle = ADC_INITSINGLE_DEFAULT;


/* Local prototype */
static float32_t convertToCelsius (int32_t adcSample);


/**************************************************************************//**
 * @brief
 *   Method to initialize the ADC to later check the battery voltage or internal temperature.
 *
 * @param[in] peripheral
 *   Select the ADC peripheral to initialize.
 *****************************************************************************/
void initADC (ADC_Measurement_t peripheral)
{
    /* Enable necessary clocks (just in case) */
    CMU_ClockEnable(cmuClock_HFPER, true); /* ADC0 is a High Frequency Peripheral */
    CMU_ClockEnable(cmuClock_ADC0, true);

    /* Set a timebase providing at least 1 us.
     * If the argument is "0" the currently defined HFPER clock setting is used. */
    init.timebase = ADC_TimebaseCalc(0);

    /* Set a prescale value according to the ADC frequency (400 000 Hz) wanted.
     * If the last argument is "0" the currently defined HFPER clock setting is for the calculation used. */
    init.prescale = ADC_PrescaleCalc(400000, 0);

    /* Initialize ADC peripheral */
    ADC_Init(ADC0, &init);

    /* Setup single conversions */

    /* initSingle.acqTime = adcAcqTime16;
     * The statement above was found in a SiLabs example but DRAMCO disabled it.
     * After testing this seemed to have no real effect so it was disabled.
     * This is probably not necessary since a prescale value other than 0 (default) has been defined. */
    if (peripheral == INTERNAL_TEMPERATURE) initSingle.input = adcSingleInpTemp; /* Internal temperature */
    else if (peripheral == BATTERY_VOLTAGE) initSingle.input = adcSingleInpVDDDiv3; /* Internal VDD/3 */
    else
    {

#if DEBUG_DBPRINT == 1 /* DEBUG_DBPRINT */
        dbcrit("Unknown ADC peripheral selected!");
#endif /* DEBUG_DBPRINT */

        /* Disable used clock */
        CMU_ClockEnable(cmuClock_ADC0, false);

        error(11);

        /* Exit function */
        return;
    }

    ADC_InitSingle(ADC0, &initSingle);

    /* Manually set some calibration values
     * ADC0->CAL = (0x7C << _ADC_CAL_SINGLEOFFSET_SHIFT) | (0x1F << _ADC_CAL_SINGLEGAIN_SHIFT);
     * The statement above was found in a SiLabs example but DRAMCO disabled it.
     * After testing this seemed to throw off the first measurement so it was disabled. */

    /* Enable interrupt on completed conversion */
    ADC_IntEnable(ADC0, ADC_IEN_SINGLE);
    NVIC_ClearPendingIRQ(ADC0_IRQn);
    NVIC_EnableIRQ(ADC0_IRQn);

    /* Disable used clock */
    CMU_ClockEnable(cmuClock_ADC0, false);

#if DEBUG_DBPRINT == 1 /* DEBUG_DBPRINT */
    if (peripheral == INTERNAL_TEMPERATURE) dbinfo("ADC0 initialized for internal temperature");
    else if (peripheral == BATTERY_VOLTAGE) dbinfo("ADC0 initialized for VBAT");
#endif /* DEBUG_DBPRINT */

}


/**************************************************************************//**
 * @brief
 *   Method to read the battery voltage or internal temperature.
 *
 * @details
 *   This method re-initializes the ADC settings if necessary.@n
 *   **Negative internal temperatures work fine.**
 *
 * @param[in] peripheral
 *   Select the ADC peripheral to read from.
 *
 * @return
 *   The measured battery voltage or internal temperature.
 *****************************************************************************/
int32_t readADC (ADC_Measurement_t peripheral)
{
    uint16_t counter = 0; /* Timeout counter */
    int32_t value = 0; /* Value to eventually return */

    /* Enable necessary clock */
    CMU_ClockEnable(cmuClock_ADC0, true);

    /* Change ADC settings if necessary */
    if (peripheral == INTERNAL_TEMPERATURE)
    {
        if (initSingle.input != adcSingleInpTemp)
        {
            initSingle.input = adcSingleInpTemp; /* Internal temperature */
            ADC_InitSingle(ADC0, &initSingle);
        }
    }
    else if (peripheral == BATTERY_VOLTAGE)
    {
        if (initSingle.input != adcSingleInpVDDDiv3)
        {
            initSingle.input = adcSingleInpVDDDiv3; /* Internal VDD/3 */
            ADC_InitSingle(ADC0, &initSingle);
        }
    }
    else
    {

#if DEBUG_DBPRINT == 1 /* DEBUG_DBPRINT */
        dbcrit("Unknown ADC peripheral selected!");
#endif /* DEBUG_DBPRINT */

        /* Disable used clock */
        CMU_ClockEnable(cmuClock_ADC0, false);

        error(12);

        /* Exit function */
        return (0);
    }

    /* Set variable false just in case */
    adcConversionComplete = false;

    /* Start single ADC conversion */
    ADC_Start(ADC0, adcStartSingle);

    /* Wait until the conversion is completed */
    while ((counter < TIMEOUT_CONVERSION) && !adcConversionComplete) counter++;

    /* Exit the function if the maximum waiting time was reached */
    if (counter == TIMEOUT_CONVERSION)
    {

#if DEBUG_DBPRINT == 1 /* DEBUG_DBPRINT */
        dbcrit("Waiting time for ADC conversion reached!");
#endif /* DEBUG_DBPRINT */

        /* Disable used clock */
        CMU_ClockEnable(cmuClock_ADC0, false);

        error(13);

        /* Exit function */
        return (0);
    }
#if DBPRINT_TIMEOUT == 1 /* DBPRINT_TIMEOUT */
    else
    {

#if DEBUG_DBPRINT == 1 /* DEBUG_DBPRINT */
        dbwarnInt("ADC conversion (", counter, ")");
#endif /* DEBUG_DBPRINT */

    }
#endif /* DBPRINT_TIMEOUT */

    /* Get the ADC value */
    value = ADC_DataSingleGet(ADC0);

    /* Disable used clock */
    CMU_ClockEnable(cmuClock_ADC0, false);

    /* Calculate final value according to parameter */
    if (peripheral == INTERNAL_TEMPERATURE)
    {
        float32_t ft = convertToCelsius(value)*1000;
        value = (int32_t) ft;
    }
    else if (peripheral == BATTERY_VOLTAGE)
    {
        float32_t fv = value * 3.75 / 4.096;
        value = (int32_t) fv;
    }

    return (value);
}


 /**************************************************************************//**
  * @brief
  *   Method to convert an ADC value to a temperature value.
  *
  * @note
  *   This is a static method because it's only internally used in this file
  *   and called by other methods if necessary.
  *
  * @param[in] adcSample
  *   The ADC sample to convert to a temperature value.
  *
  * @return
  *   The converted temperature value.
  *****************************************************************************/
static float32_t convertToCelsius (int32_t adcSample)
{
    float32_t temp;

    /* Factory calibration temperature from device information page. */
    int32_t cal_temp_0 = ((DEVINFO->CAL & _DEVINFO_CAL_TEMP_MASK)
                        >> _DEVINFO_CAL_TEMP_SHIFT);

    /* Factory calibration value from device information page. */
    int32_t cal_value_0 = ((DEVINFO->ADC0CAL2 & _DEVINFO_ADC0CAL2_TEMP1V25_MASK)
                         >> _DEVINFO_ADC0CAL2_TEMP1V25_SHIFT);

    /* Temperature gradient (from datasheet) */
    float32_t t_grad = -6.27;

    temp = (cal_temp_0 - ((cal_value_0 - adcSample) / t_grad));

    return (temp);
}


/**************************************************************************//**
 * @brief
 *   Interrupt Service Routine for ADC0.
 *****************************************************************************/
void ADC0_IRQHandler (void)
{
    /* Read interrupt flags */
     uint32_t flags = ADC_IntGet(ADC0);

    /* Clear the ADC0 interrupt flags */
    ADC_IntClear(ADC0, flags);

    /* Indicate that an ADC conversion has been completed */
    adcConversionComplete = true;
}