AMiRo-OS

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#include "vl53l0x_api.h"

#include "vl53l0x_api_core.h"

#include "vl53l0x_api_calibration.h"

#ifndef __KERNEL__

#include <stdlib.h>

#endif

#define LOG_FUNCTION_START(fmt, ...) \

    _LOG_FUNCTION_START(TRACE_MODULE_API, fmt, ##__VA_ARGS__)

#define LOG_FUNCTION_END(status, ...) \

    _LOG_FUNCTION_END(TRACE_MODULE_API, status, ##__VA_ARGS__)

#define LOG_FUNCTION_END_FMT(status, fmt, ...) \

    _LOG_FUNCTION_END_FMT(TRACE_MODULE_API, status, fmt, ##__VA_ARGS__)

#define REF_ARRAY_SPAD_0  0

#define REF_ARRAY_SPAD_5  5

#define REF_ARRAY_SPAD_10 10

uint32_t refArrayQuadrants[4] = {REF_ARRAY_SPAD_10, REF_ARRAY_SPAD_5,

        REF_ARRAY_SPAD_0, REF_ARRAY_SPAD_5 };

VL53L0X_Error VL53L0X_perform_xtalk_calibration(VL53L0X_DEV Dev,

            FixPoint1616_t XTalkCalDistance,

            FixPoint1616_t *pXTalkCompensationRateMegaCps)

{

    VL53L0X_Error Status = VL53L0X_ERROR_NONE;

    uint16_t sum_ranging = 0;

    uint16_t sum_spads = 0;

    FixPoint1616_t sum_signalRate = 0;

    FixPoint1616_t total_count = 0;

    uint8_t xtalk_meas = 0;

    VL53L0X_RangingMeasurementData_t RangingMeasurementData;

    FixPoint1616_t xTalkStoredMeanSignalRate;

    FixPoint1616_t xTalkStoredMeanRange;

    FixPoint1616_t xTalkStoredMeanRtnSpads;

    uint32_t signalXTalkTotalPerSpad;

    uint32_t xTalkStoredMeanRtnSpadsAsInt;

    uint32_t xTalkCalDistanceAsInt;

    FixPoint1616_t XTalkCompensationRateMegaCps;

    if (XTalkCalDistance <= 0)

        Status = VL53L0X_ERROR_INVALID_PARAMS;

    /* Disable the XTalk compensation */

    if (Status == VL53L0X_ERROR_NONE)

        Status = VL53L0X_SetXTalkCompensationEnable(Dev, 0);

    /* Disable the RIT */

    if (Status == VL53L0X_ERROR_NONE) {

        Status = VL53L0X_SetLimitCheckEnable(Dev,

                VL53L0X_CHECKENABLE_RANGE_IGNORE_THRESHOLD, 0);

    }

    /* Perform 50 measurements and compute the averages */

    if (Status == VL53L0X_ERROR_NONE) {

        sum_ranging = 0;

        sum_spads = 0;

        sum_signalRate = 0;

        total_count = 0;

        for (xtalk_meas = 0; xtalk_meas < 50; xtalk_meas++) {

            Status = VL53L0X_PerformSingleRangingMeasurement(Dev,

                &RangingMeasurementData);

            if (Status != VL53L0X_ERROR_NONE)

                break;

            /* The range is valid when RangeStatus = 0 */

            if (RangingMeasurementData.RangeStatus == 0) {

                sum_ranging = sum_ranging +

                    RangingMeasurementData.RangeMilliMeter;

                sum_signalRate = sum_signalRate +

                RangingMeasurementData.SignalRateRtnMegaCps;

                sum_spads = sum_spads +

                RangingMeasurementData.EffectiveSpadRtnCount

                    / 256;

                total_count = total_count + 1;

            }

        }

        /* no valid values found */

        if (total_count == 0)

            Status = VL53L0X_ERROR_RANGE_ERROR;

    }

    if (Status == VL53L0X_ERROR_NONE) {

        /* FixPoint1616_t / uint16_t = FixPoint1616_t */

        xTalkStoredMeanSignalRate = sum_signalRate / total_count;

        xTalkStoredMeanRange = (FixPoint1616_t)((uint32_t)(

            sum_ranging << 16) / total_count);

        xTalkStoredMeanRtnSpads = (FixPoint1616_t)((uint32_t)(

            sum_spads << 16) / total_count);

        /* Round Mean Spads to Whole Number.

         * Typically the calculated mean SPAD count is a whole number

         * or very close to a whole

         * number, therefore any truncation will not result in a

         * significant loss in accuracy.

         * Also, for a grey target at a typical distance of around

         * 400mm, around 220 SPADs will

         * be enabled, therefore, any truncation will result in a loss

         * of accuracy of less than

         * 0.5%.

         */

        xTalkStoredMeanRtnSpadsAsInt = (xTalkStoredMeanRtnSpads +

            0x8000) >> 16;

        /* Round Cal Distance to Whole Number.

         * Note that the cal distance is in mm, therefore no resolution

         * is lost.*/

         xTalkCalDistanceAsInt = (XTalkCalDistance + 0x8000) >> 16;

        if (xTalkStoredMeanRtnSpadsAsInt == 0 ||

           xTalkCalDistanceAsInt == 0 ||

           xTalkStoredMeanRange >= XTalkCalDistance) {

            XTalkCompensationRateMegaCps = 0;

        } else {

            /* Round Cal Distance to Whole Number.

               Note that the cal distance is in mm, therefore no

               resolution is lost.*/

            xTalkCalDistanceAsInt = (XTalkCalDistance +

                0x8000) >> 16;

            /* Apply division by mean spad count early in the

             * calculation to keep the numbers small.

             * This ensures we can maintain a 32bit calculation.

             * Fixed1616 / int := Fixed1616 */

            signalXTalkTotalPerSpad = (xTalkStoredMeanSignalRate) /

                xTalkStoredMeanRtnSpadsAsInt;

            /* Complete the calculation for total Signal XTalk per

             * SPAD

             * Fixed1616 * (Fixed1616 - Fixed1616/int) :=

             * (2^16 * Fixed1616)

             */

            signalXTalkTotalPerSpad *= ((1 << 16) -

                (xTalkStoredMeanRange / xTalkCalDistanceAsInt));

            /* Round from 2^16 * Fixed1616, to Fixed1616. */

            XTalkCompensationRateMegaCps = (signalXTalkTotalPerSpad

                + 0x8000) >> 16;

        }

        *pXTalkCompensationRateMegaCps = XTalkCompensationRateMegaCps;

        /* Enable the XTalk compensation */

        if (Status == VL53L0X_ERROR_NONE)

            Status = VL53L0X_SetXTalkCompensationEnable(Dev, 1);

        /* Enable the XTalk compensation */

        if (Status == VL53L0X_ERROR_NONE)

            Status = VL53L0X_SetXTalkCompensationRateMegaCps(Dev,

                    XTalkCompensationRateMegaCps);

    }

    return Status;

}

VL53L0X_Error VL53L0X_perform_offset_calibration(VL53L0X_DEV Dev,

            FixPoint1616_t CalDistanceMilliMeter,

            int32_t *pOffsetMicroMeter)

{

    VL53L0X_Error Status = VL53L0X_ERROR_NONE;

    uint16_t sum_ranging = 0;

    FixPoint1616_t total_count = 0;

    VL53L0X_RangingMeasurementData_t RangingMeasurementData;

    FixPoint1616_t StoredMeanRange;

    uint32_t StoredMeanRangeAsInt;

    uint32_t CalDistanceAsInt_mm;

    uint8_t SequenceStepEnabled;

    int meas = 0;

    if (CalDistanceMilliMeter <= 0)

        Status = VL53L0X_ERROR_INVALID_PARAMS;

    if (Status == VL53L0X_ERROR_NONE)

        Status = VL53L0X_SetOffsetCalibrationDataMicroMeter(Dev, 0);

    /* Get the value of the TCC */

    if (Status == VL53L0X_ERROR_NONE)

        Status = VL53L0X_GetSequenceStepEnable(Dev,

                VL53L0X_SEQUENCESTEP_TCC, &SequenceStepEnabled);

    /* Disable the TCC */

    if (Status == VL53L0X_ERROR_NONE)

        Status = VL53L0X_SetSequenceStepEnable(Dev,

                VL53L0X_SEQUENCESTEP_TCC, 0);

    /* Disable the RIT */

    if (Status == VL53L0X_ERROR_NONE)

        Status = VL53L0X_SetLimitCheckEnable(Dev,

                VL53L0X_CHECKENABLE_RANGE_IGNORE_THRESHOLD, 0);

    /* Perform 50 measurements and compute the averages */

    if (Status == VL53L0X_ERROR_NONE) {

        sum_ranging = 0;

        total_count = 0;

        for (meas = 0; meas < 50; meas++) {

            Status = VL53L0X_PerformSingleRangingMeasurement(Dev,

                    &RangingMeasurementData);

            if (Status != VL53L0X_ERROR_NONE)

                break;

            /* The range is valid when RangeStatus = 0 */

            if (RangingMeasurementData.RangeStatus == 0) {

                sum_ranging = sum_ranging +

                    RangingMeasurementData.RangeMilliMeter;

                total_count = total_count + 1;

            }

        }

        /* no valid values found */

        if (total_count == 0)

            Status = VL53L0X_ERROR_RANGE_ERROR;

    }

    if (Status == VL53L0X_ERROR_NONE) {

        /* FixPoint1616_t / uint16_t = FixPoint1616_t */

        StoredMeanRange = (FixPoint1616_t)((uint32_t)(sum_ranging << 16)

            / total_count);

        StoredMeanRangeAsInt = (StoredMeanRange + 0x8000) >> 16;

        /* Round Cal Distance to Whole Number.

         * Note that the cal distance is in mm, therefore no resolution

         * is lost.*/

         CalDistanceAsInt_mm = (CalDistanceMilliMeter + 0x8000) >> 16;

         *pOffsetMicroMeter = (CalDistanceAsInt_mm -

                 StoredMeanRangeAsInt) * 1000;

        /* Apply the calculated offset */

        if (Status == VL53L0X_ERROR_NONE) {

            VL53L0X_SETPARAMETERFIELD(Dev, RangeOffsetMicroMeters,

                    *pOffsetMicroMeter);

            Status = VL53L0X_SetOffsetCalibrationDataMicroMeter(Dev,

                    *pOffsetMicroMeter);

        }

    }

    /* Restore the TCC */

    if (Status == VL53L0X_ERROR_NONE) {

        if (SequenceStepEnabled != 0)

            Status = VL53L0X_SetSequenceStepEnable(Dev,

                    VL53L0X_SEQUENCESTEP_TCC, 1);

    }

    return Status;

}

VL53L0X_Error VL53L0X_set_offset_calibration_data_micro_meter(VL53L0X_DEV Dev,

        int32_t OffsetCalibrationDataMicroMeter)

{

    VL53L0X_Error Status = VL53L0X_ERROR_NONE;

    int32_t cMaxOffsetMicroMeter = 511000;

    int32_t cMinOffsetMicroMeter = -512000;

    int16_t cOffsetRange = 4096;

    uint32_t encodedOffsetVal;

    LOG_FUNCTION_START("");

    if (OffsetCalibrationDataMicroMeter > cMaxOffsetMicroMeter)

        OffsetCalibrationDataMicroMeter = cMaxOffsetMicroMeter;

    else if (OffsetCalibrationDataMicroMeter < cMinOffsetMicroMeter)

        OffsetCalibrationDataMicroMeter = cMinOffsetMicroMeter;

    /* The offset register is 10.2 format and units are mm

     * therefore conversion is applied by a division of

     * 250.

     */

    if (OffsetCalibrationDataMicroMeter >= 0) {

        encodedOffsetVal =

            OffsetCalibrationDataMicroMeter/250;

    } else {

        encodedOffsetVal =

            cOffsetRange +

            OffsetCalibrationDataMicroMeter/250;

    }

    Status = VL53L0X_WrWord(Dev,

        VL53L0X_REG_ALGO_PART_TO_PART_RANGE_OFFSET_MM,

        encodedOffsetVal);

    LOG_FUNCTION_END(Status);

    return Status;

}

VL53L0X_Error VL53L0X_get_offset_calibration_data_micro_meter(VL53L0X_DEV Dev,

        int32_t *pOffsetCalibrationDataMicroMeter)

{

    VL53L0X_Error Status = VL53L0X_ERROR_NONE;

    uint16_t RangeOffsetRegister;

    int16_t cMaxOffset = 2047;

    int16_t cOffsetRange = 4096;

    /* Note that offset has 10.2 format */

    Status = VL53L0X_RdWord(Dev,

                VL53L0X_REG_ALGO_PART_TO_PART_RANGE_OFFSET_MM,

                &RangeOffsetRegister);

    if (Status == VL53L0X_ERROR_NONE) {

        RangeOffsetRegister = (RangeOffsetRegister & 0x0fff);

        /* Apply 12 bit 2's compliment conversion */

        if (RangeOffsetRegister > cMaxOffset)

            *pOffsetCalibrationDataMicroMeter =

                (int16_t)(RangeOffsetRegister - cOffsetRange)

                    * 250;

        else

            *pOffsetCalibrationDataMicroMeter =

                (int16_t)RangeOffsetRegister * 250;

    }

    return Status;

}

VL53L0X_Error VL53L0X_apply_offset_adjustment(VL53L0X_DEV Dev)

{

    VL53L0X_Error Status = VL53L0X_ERROR_NONE;

    int32_t CorrectedOffsetMicroMeters;

    int32_t CurrentOffsetMicroMeters;

    /* if we run on this function we can read all the NVM info

     * used by the API */

    Status = VL53L0X_get_info_from_device(Dev, 7);

    /* Read back current device offset */

    if (Status == VL53L0X_ERROR_NONE) {

        Status = VL53L0X_GetOffsetCalibrationDataMicroMeter(Dev,

                    &CurrentOffsetMicroMeters);

    }

    /* Apply Offset Adjustment derived from 400mm measurements */

    if (Status == VL53L0X_ERROR_NONE) {

        /* Store initial device offset */

        PALDevDataSet(Dev, Part2PartOffsetNVMMicroMeter,

            CurrentOffsetMicroMeters);

        CorrectedOffsetMicroMeters = CurrentOffsetMicroMeters +

            (int32_t)PALDevDataGet(Dev,

                Part2PartOffsetAdjustmentNVMMicroMeter);

        Status = VL53L0X_SetOffsetCalibrationDataMicroMeter(Dev,

                    CorrectedOffsetMicroMeters);

        /* store current, adjusted offset */

        if (Status == VL53L0X_ERROR_NONE) {

            VL53L0X_SETPARAMETERFIELD(Dev, RangeOffsetMicroMeters,

                    CorrectedOffsetMicroMeters);

        }

    }

    return Status;

}

void get_next_good_spad(uint8_t goodSpadArray[], uint32_t size,

            uint32_t curr, int32_t *next)

{

    uint32_t startIndex;

    uint32_t fineOffset;

    uint32_t cSpadsPerByte = 8;

    uint32_t coarseIndex;

    uint32_t fineIndex;

    uint8_t dataByte;

    uint8_t success = 0;

    /*

     * Starting with the current good spad, loop through the array to find

     * the next. i.e. the next bit set in the sequence.

     *

     * The coarse index is the byte index of the array and the fine index is

     * the index of the bit within each byte.

     */

    *next = -1;

    startIndex = curr / cSpadsPerByte;

    fineOffset = curr % cSpadsPerByte;

    for (coarseIndex = startIndex; ((coarseIndex < size) && !success);

                coarseIndex++) {

        fineIndex = 0;

        dataByte = goodSpadArray[coarseIndex];

        if (coarseIndex == startIndex) {

            /* locate the bit position of the provided current

             * spad bit before iterating */

            dataByte >>= fineOffset;

            fineIndex = fineOffset;

        }

        while (fineIndex < cSpadsPerByte) {

            if ((dataByte & 0x1) == 1) {

                success = 1;

                *next = coarseIndex * cSpadsPerByte + fineIndex;

                break;

            }

            dataByte >>= 1;

            fineIndex++;

        }

    }

}

uint8_t is_aperture(uint32_t spadIndex)

{

    /*

     * This function reports if a given spad index is an aperture SPAD by

     * deriving the quadrant.

     */

    uint32_t quadrant;

    uint8_t isAperture = 1;

    quadrant = spadIndex >> 6;

    if (refArrayQuadrants[quadrant] == REF_ARRAY_SPAD_0)

        isAperture = 0;

    return isAperture;

}

VL53L0X_Error enable_spad_bit(uint8_t spadArray[], uint32_t size,

    uint32_t spadIndex)

{

    VL53L0X_Error status = VL53L0X_ERROR_NONE;

    uint32_t cSpadsPerByte = 8;

    uint32_t coarseIndex;

    uint32_t fineIndex;

    coarseIndex = spadIndex / cSpadsPerByte;

    fineIndex = spadIndex % cSpadsPerByte;

    if (coarseIndex >= size)

        status = VL53L0X_ERROR_REF_SPAD_INIT;

    else

        spadArray[coarseIndex] |= (1 << fineIndex);

    return status;

}

VL53L0X_Error count_enabled_spads(uint8_t spadArray[],

        uint32_t byteCount, uint32_t maxSpads,

        uint32_t *pTotalSpadsEnabled, uint8_t *pIsAperture)

{

    VL53L0X_Error status = VL53L0X_ERROR_NONE;

    uint32_t cSpadsPerByte = 8;

    uint32_t lastByte;

    uint32_t lastBit;

    uint32_t byteIndex = 0;

    uint32_t bitIndex = 0;

    uint8_t tempByte;

    uint8_t spadTypeIdentified = 0;

    /* The entire array will not be used for spads, therefore the last

     * byte and last bit is determined from the max spads value.

     */

    lastByte = maxSpads / cSpadsPerByte;

    lastBit = maxSpads % cSpadsPerByte;

    /* Check that the max spads value does not exceed the array bounds. */

    if (lastByte >= byteCount)

        status = VL53L0X_ERROR_REF_SPAD_INIT;

    *pTotalSpadsEnabled = 0;

    /* Count the bits enabled in the whole bytes */

    for (byteIndex = 0; byteIndex <= (lastByte - 1); byteIndex++) {

        tempByte = spadArray[byteIndex];

        for (bitIndex = 0; bitIndex <= cSpadsPerByte; bitIndex++) {

            if ((tempByte & 0x01) == 1) {

                (*pTotalSpadsEnabled)++;

                if (!spadTypeIdentified) {

                    *pIsAperture = 1;

                    if ((byteIndex < 2) && (bitIndex < 4))

                            *pIsAperture = 0;

                    spadTypeIdentified = 1;

                }

            }

            tempByte >>= 1;

        }

    }

    /* Count the number of bits enabled in the last byte accounting

     * for the fact that not all bits in the byte may be used.

     */

    tempByte = spadArray[lastByte];

    for (bitIndex = 0; bitIndex <= lastBit; bitIndex++) {

        if ((tempByte & 0x01) == 1)

            (*pTotalSpadsEnabled)++;

    }

    return status;

}

VL53L0X_Error set_ref_spad_map(VL53L0X_DEV Dev, uint8_t *refSpadArray)

{

    VL53L0X_Error status = VL53L0X_WriteMulti(Dev,

                VL53L0X_REG_GLOBAL_CONFIG_SPAD_ENABLES_REF_0,

                refSpadArray, 6);

    return status;

}

VL53L0X_Error get_ref_spad_map(VL53L0X_DEV Dev, uint8_t *refSpadArray)

{

    VL53L0X_Error status = VL53L0X_ReadMulti(Dev,

                VL53L0X_REG_GLOBAL_CONFIG_SPAD_ENABLES_REF_0,

                refSpadArray,

                6);

    return status;

}

VL53L0X_Error enable_ref_spads(VL53L0X_DEV Dev,

                uint8_t apertureSpads,

                uint8_t goodSpadArray[],

                uint8_t spadArray[],

                uint32_t size,

                uint32_t start,

                uint32_t offset,

                uint32_t spadCount,

                uint32_t *lastSpad)

{

    VL53L0X_Error status = VL53L0X_ERROR_NONE;

    uint32_t index;

    uint32_t i;

    int32_t nextGoodSpad = offset;

    uint32_t currentSpad;

    uint8_t checkSpadArray[6];

    /*

     * This function takes in a spad array which may or may not have SPADS

     * already enabled and appends from a given offset a requested number

     * of new SPAD enables. The 'good spad map' is applied to

     * determine the next SPADs to enable.

     *

     * This function applies to only aperture or only non-aperture spads.

     * Checks are performed to ensure this.

     */

    currentSpad = offset;

    for (index = 0; index < spadCount; index++) {

        get_next_good_spad(goodSpadArray, size, currentSpad,

            &nextGoodSpad);

        if (nextGoodSpad == -1) {

            status = VL53L0X_ERROR_REF_SPAD_INIT;

            break;

        }

        /* Confirm that the next good SPAD is non-aperture */

        if (is_aperture(start + nextGoodSpad) != apertureSpads) {

            /* if we can't get the required number of good aperture

             * spads from the current quadrant then this is an error

             */

            status = VL53L0X_ERROR_REF_SPAD_INIT;

            break;

        }

        currentSpad = (uint32_t)nextGoodSpad;

        enable_spad_bit(spadArray, size, currentSpad);

        currentSpad++;

    }

    *lastSpad = currentSpad;

    if (status == VL53L0X_ERROR_NONE)

        status = set_ref_spad_map(Dev, spadArray);

    if (status == VL53L0X_ERROR_NONE) {

        status = get_ref_spad_map(Dev, checkSpadArray);

        i = 0;

        /* Compare spad maps. If not equal report error. */

        while (i < size) {

            if (spadArray[i] != checkSpadArray[i]) {

                status = VL53L0X_ERROR_REF_SPAD_INIT;

                break;

            }

            i++;

        }

    }

    return status;

}

VL53L0X_Error perform_ref_signal_measurement(VL53L0X_DEV Dev,

        uint16_t *refSignalRate)

{

    VL53L0X_Error status = VL53L0X_ERROR_NONE;

    VL53L0X_RangingMeasurementData_t rangingMeasurementData;

    uint8_t SequenceConfig = 0;

    /* store the value of the sequence config,

     * this will be reset before the end of the function

     */

    SequenceConfig = PALDevDataGet(Dev, SequenceConfig);

    /*

     * This function performs a reference signal rate measurement.

     */

    if (status == VL53L0X_ERROR_NONE)

        status = VL53L0X_WrByte(Dev,

            VL53L0X_REG_SYSTEM_SEQUENCE_CONFIG, 0xC0);

    if (status == VL53L0X_ERROR_NONE)

        status = VL53L0X_PerformSingleRangingMeasurement(Dev,

                &rangingMeasurementData);

    if (status == VL53L0X_ERROR_NONE)

        status = VL53L0X_WrByte(Dev, 0xFF, 0x01);

    if (status == VL53L0X_ERROR_NONE)

        status = VL53L0X_RdWord(Dev,

            VL53L0X_REG_RESULT_PEAK_SIGNAL_RATE_REF,

            refSignalRate);

    if (status == VL53L0X_ERROR_NONE)

        status = VL53L0X_WrByte(Dev, 0xFF, 0x00);

    if (status == VL53L0X_ERROR_NONE) {

        /* restore the previous Sequence Config */

        status = VL53L0X_WrByte(Dev, VL53L0X_REG_SYSTEM_SEQUENCE_CONFIG,

                SequenceConfig);

        if (status == VL53L0X_ERROR_NONE)

            PALDevDataSet(Dev, SequenceConfig, SequenceConfig);

    }

    return status;

}

VL53L0X_Error VL53L0X_perform_ref_spad_management(VL53L0X_DEV Dev,

                uint32_t *refSpadCount,

                uint8_t *isApertureSpads)

{

    VL53L0X_Error Status = VL53L0X_ERROR_NONE;

    uint8_t lastSpadArray[6];

    uint8_t startSelect = 0xB4;

    uint32_t minimumSpadCount = 3;

    uint32_t maxSpadCount = 44;

    uint32_t currentSpadIndex = 0;

    uint32_t lastSpadIndex = 0;

    int32_t nextGoodSpad = 0;

    uint16_t targetRefRate = 0x0A00; /* 20 MCPS in 9:7 format */

    uint16_t peakSignalRateRef;

    uint32_t needAptSpads = 0;

    uint32_t index = 0;

    uint32_t spadArraySize = 6;

    uint32_t signalRateDiff = 0;

    uint32_t lastSignalRateDiff = 0;

    uint8_t complete = 0;

    uint8_t VhvSettings = 0;

    uint8_t PhaseCal = 0;

    uint32_t refSpadCount_int = 0;

    uint8_t         isApertureSpads_int = 0;

    /*

     * The reference SPAD initialization procedure determines the minimum

     * amount of reference spads to be enables to achieve a target reference

     * signal rate and should be performed once during initialization.

     *

     * Either aperture or non-aperture spads are applied but never both.

     * Firstly non-aperture spads are set, begining with 5 spads, and

     * increased one spad at a time until the closest measurement to the

     * target rate is achieved.

     *

     * If the target rate is exceeded when 5 non-aperture spads are enabled,

     * initialization is performed instead with aperture spads.

     *

     * When setting spads, a 'Good Spad Map' is applied.

     *

     * This procedure operates within a SPAD window of interest of a maximum

     * 44 spads.

     * The start point is currently fixed to 180, which lies towards the end

     * of the non-aperture quadrant and runs in to the adjacent aperture

     * quadrant.

     */

    targetRefRate = PALDevDataGet(Dev, targetRefRate);

    /*

     * Initialize Spad arrays.

     * Currently the good spad map is initialised to 'All good'.

     * This is a short term implementation. The good spad map will be

     * provided as an input.

     * Note that there are 6 bytes. Only the first 44 bits will be used to

     * represent spads.

     */

    for (index = 0; index < spadArraySize; index++)

        Dev->Data.SpadData.RefSpadEnables[index] = 0;

    Status = VL53L0X_WrByte(Dev, 0xFF, 0x01);

    if (Status == VL53L0X_ERROR_NONE)

        Status = VL53L0X_WrByte(Dev,

            VL53L0X_REG_DYNAMIC_SPAD_REF_EN_START_OFFSET, 0x00);

    if (Status == VL53L0X_ERROR_NONE)

        Status = VL53L0X_WrByte(Dev,

            VL53L0X_REG_DYNAMIC_SPAD_NUM_REQUESTED_REF_SPAD, 0x2C);

    if (Status == VL53L0X_ERROR_NONE)

        Status = VL53L0X_WrByte(Dev, 0xFF, 0x00);

    if (Status == VL53L0X_ERROR_NONE)

        Status = VL53L0X_WrByte(Dev,

            VL53L0X_REG_GLOBAL_CONFIG_REF_EN_START_SELECT,

            startSelect);

    if (Status == VL53L0X_ERROR_NONE)

        Status = VL53L0X_WrByte(Dev,

                VL53L0X_REG_POWER_MANAGEMENT_GO1_POWER_FORCE, 0);

    /* Perform ref calibration */

    if (Status == VL53L0X_ERROR_NONE)

        Status = VL53L0X_perform_ref_calibration(Dev, &VhvSettings,

            &PhaseCal, 0);

    if (Status == VL53L0X_ERROR_NONE) {

        /* Enable Minimum NON-APERTURE Spads */

        currentSpadIndex = 0;

        lastSpadIndex = currentSpadIndex;

        needAptSpads = 0;

        Status = enable_ref_spads(Dev,

                    needAptSpads,

                    Dev->Data.SpadData.RefGoodSpadMap,

                    Dev->Data.SpadData.RefSpadEnables,

                    spadArraySize,

                    startSelect,

                    currentSpadIndex,

                    minimumSpadCount,

                    &lastSpadIndex);

    }

    if (Status == VL53L0X_ERROR_NONE) {

        currentSpadIndex = lastSpadIndex;

        Status = perform_ref_signal_measurement(Dev,

            &peakSignalRateRef);

        if ((Status == VL53L0X_ERROR_NONE) &&

            (peakSignalRateRef > targetRefRate)) {

            /* Signal rate measurement too high,

             * switch to APERTURE SPADs */

            for (index = 0; index < spadArraySize; index++)

                Dev->Data.SpadData.RefSpadEnables[index] = 0;

            /* Increment to the first APERTURE spad */

            while ((is_aperture(startSelect + currentSpadIndex)

                == 0) && (currentSpadIndex < maxSpadCount)) {

                currentSpadIndex++;

            }

            needAptSpads = 1;

            Status = enable_ref_spads(Dev,

                    needAptSpads,

                    Dev->Data.SpadData.RefGoodSpadMap,

                    Dev->Data.SpadData.RefSpadEnables,

                    spadArraySize,

                    startSelect,

                    currentSpadIndex,

                    minimumSpadCount,

                    &lastSpadIndex);

            if (Status == VL53L0X_ERROR_NONE) {

                currentSpadIndex = lastSpadIndex;

                Status = perform_ref_signal_measurement(Dev,

                        &peakSignalRateRef);

                if ((Status == VL53L0X_ERROR_NONE) &&

                    (peakSignalRateRef > targetRefRate)) {

                    /* Signal rate still too high after

                     * setting the minimum number of

                     * APERTURE spads. Can do no more

                     * therefore set the min number of

                     * aperture spads as the result.

                     */

                    isApertureSpads_int = 1;

                    refSpadCount_int = minimumSpadCount;

                }

            }

        } else {

            needAptSpads = 0;

        }

    }

    if ((Status == VL53L0X_ERROR_NONE) &&

        (peakSignalRateRef < targetRefRate)) {

        /* At this point, the minimum number of either aperture

         * or non-aperture spads have been set. Proceed to add

         * spads and perform measurements until the target

         * reference is reached.

         */

        isApertureSpads_int = needAptSpads;

        refSpadCount_int        = minimumSpadCount;

        memcpy(lastSpadArray, Dev->Data.SpadData.RefSpadEnables,

                spadArraySize);

        lastSignalRateDiff = abs(peakSignalRateRef -

            targetRefRate);

        complete = 0;

        while (!complete) {

            get_next_good_spad(

                Dev->Data.SpadData.RefGoodSpadMap,

                spadArraySize, currentSpadIndex,

                &nextGoodSpad);

            if (nextGoodSpad == -1) {

                Status = VL53L0X_ERROR_REF_SPAD_INIT;

                break;

            }

            /* Cannot combine Aperture and Non-Aperture spads, so

             * ensure the current spad is of the correct type.

             */

            if (is_aperture((uint32_t)startSelect + nextGoodSpad) !=

                    needAptSpads) {

                /* At this point we have enabled the maximum

                 * number of Aperture spads.

                 */

                complete = 1;

                break;

            }

            (refSpadCount_int)++;

            currentSpadIndex = nextGoodSpad;

            Status = enable_spad_bit(

                    Dev->Data.SpadData.RefSpadEnables,

                    spadArraySize, currentSpadIndex);

            if (Status == VL53L0X_ERROR_NONE) {

                currentSpadIndex++;

                /* Proceed to apply the additional spad and

                 * perform measurement. */

                Status = set_ref_spad_map(Dev,

                    Dev->Data.SpadData.RefSpadEnables);

            }

            if (Status != VL53L0X_ERROR_NONE)

                break;

            Status = perform_ref_signal_measurement(Dev,

                    &peakSignalRateRef);

            if (Status != VL53L0X_ERROR_NONE)

                break;

            signalRateDiff = abs(peakSignalRateRef - targetRefRate);

            if (peakSignalRateRef > targetRefRate) {

                /* Select the spad map that provides the

                 * measurement closest to the target rate,

                 * either above or below it.

                 */

                if (signalRateDiff > lastSignalRateDiff) {

                    /* Previous spad map produced a closer

                     * measurement, so choose this. */

                    Status = set_ref_spad_map(Dev,

                            lastSpadArray);

                    memcpy(

                    Dev->Data.SpadData.RefSpadEnables,

                    lastSpadArray, spadArraySize);

                    (refSpadCount_int)--;

                }

                complete = 1;

            } else {

                /* Continue to add spads */

                lastSignalRateDiff = signalRateDiff;

                memcpy(lastSpadArray,

                    Dev->Data.SpadData.RefSpadEnables,

                    spadArraySize);

            }

        } /* while */

    }

    if (Status == VL53L0X_ERROR_NONE) {

        *refSpadCount = refSpadCount_int;

        *isApertureSpads = isApertureSpads_int;

        VL53L0X_SETDEVICESPECIFICPARAMETER(Dev, RefSpadsInitialised, 1);

        VL53L0X_SETDEVICESPECIFICPARAMETER(Dev,

            ReferenceSpadCount, (uint8_t)(*refSpadCount));

        VL53L0X_SETDEVICESPECIFICPARAMETER(Dev,

            ReferenceSpadType, *isApertureSpads);

    }

    return Status;

}

VL53L0X_Error VL53L0X_set_reference_spads(VL53L0X_DEV Dev,

                 uint32_t count, uint8_t isApertureSpads)

{

    VL53L0X_Error Status = VL53L0X_ERROR_NONE;

    uint32_t currentSpadIndex = 0;

    uint8_t startSelect = 0xB4;

    uint32_t spadArraySize = 6;

    uint32_t maxSpadCount = 44;

    uint32_t lastSpadIndex;

    uint32_t index;

    /*

     * This function applies a requested number of reference spads, either

     * aperture or

     * non-aperture, as requested.

     * The good spad map will be applied.

     */

    Status = VL53L0X_WrByte(Dev, 0xFF, 0x01);

    if (Status == VL53L0X_ERROR_NONE)

        Status = VL53L0X_WrByte(Dev,

            VL53L0X_REG_DYNAMIC_SPAD_REF_EN_START_OFFSET, 0x00);

    if (Status == VL53L0X_ERROR_NONE)

        Status = VL53L0X_WrByte(Dev,

            VL53L0X_REG_DYNAMIC_SPAD_NUM_REQUESTED_REF_SPAD, 0x2C);

    if (Status == VL53L0X_ERROR_NONE)

        Status = VL53L0X_WrByte(Dev, 0xFF, 0x00);

    if (Status == VL53L0X_ERROR_NONE)

        Status = VL53L0X_WrByte(Dev,

            VL53L0X_REG_GLOBAL_CONFIG_REF_EN_START_SELECT,

            startSelect);

    for (index = 0; index < spadArraySize; index++)

        Dev->Data.SpadData.RefSpadEnables[index] = 0;

    if (isApertureSpads) {

        /* Increment to the first APERTURE spad */

        while ((is_aperture(startSelect + currentSpadIndex) == 0) &&

              (currentSpadIndex < maxSpadCount)) {

            currentSpadIndex++;

        }

    }

    Status = enable_ref_spads(Dev,

                isApertureSpads,

                Dev->Data.SpadData.RefGoodSpadMap,

                Dev->Data.SpadData.RefSpadEnables,

                spadArraySize,

                startSelect,

                currentSpadIndex,

                count,

                &lastSpadIndex);

    if (Status == VL53L0X_ERROR_NONE) {

        VL53L0X_SETDEVICESPECIFICPARAMETER(Dev, RefSpadsInitialised, 1);

        VL53L0X_SETDEVICESPECIFICPARAMETER(Dev,

            ReferenceSpadCount, (uint8_t)(count));

        VL53L0X_SETDEVICESPECIFICPARAMETER(Dev,

            ReferenceSpadType, isApertureSpads);

    }

    return Status;

}

VL53L0X_Error VL53L0X_get_reference_spads(VL53L0X_DEV Dev,

            uint32_t *pSpadCount, uint8_t *pIsApertureSpads)

{

    VL53L0X_Error Status = VL53L0X_ERROR_NONE;

    uint8_t refSpadsInitialised;

    uint8_t refSpadArray[6];

    uint32_t cMaxSpadCount = 44;

    uint32_t cSpadArraySize = 6;

    uint32_t spadsEnabled;

    uint8_t isApertureSpads = 0;

    refSpadsInitialised = VL53L0X_GETDEVICESPECIFICPARAMETER(Dev,

                    RefSpadsInitialised);

    if (refSpadsInitialised == 1) {

        *pSpadCount = (uint32_t)VL53L0X_GETDEVICESPECIFICPARAMETER(Dev,

            ReferenceSpadCount);

        *pIsApertureSpads = VL53L0X_GETDEVICESPECIFICPARAMETER(Dev,

            ReferenceSpadType);

    } else {

        /* obtain spad info from device.*/

        Status = get_ref_spad_map(Dev, refSpadArray);

        if (Status == VL53L0X_ERROR_NONE) {

            /* count enabled spads within spad map array and

             * determine if Aperture or Non-Aperture.

             */

            Status = count_enabled_spads(refSpadArray,

                            cSpadArraySize,

                            cMaxSpadCount,

                            &spadsEnabled,

                            &isApertureSpads);

            if (Status == VL53L0X_ERROR_NONE) {

                *pSpadCount = spadsEnabled;

                *pIsApertureSpads = isApertureSpads;

                VL53L0X_SETDEVICESPECIFICPARAMETER(Dev,

                    RefSpadsInitialised, 1);

                VL53L0X_SETDEVICESPECIFICPARAMETER(Dev,

                    ReferenceSpadCount,

                    (uint8_t)spadsEnabled);

                VL53L0X_SETDEVICESPECIFICPARAMETER(Dev,