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PSoC™ 4 Forum Discussions

mabe_1339641
Level 1
Level 1

Hello,

I am using CY8C4124AZI-S413 (supplied with 5V) to read a voltage value using CapSense_ADC (release 5.0) block.

I need the formula to calculate raw to mV and viceversa.

Could someone help me, please?

Thanks

Regards

Mauro Berioli

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1 Solution
Vison_Zhang
Moderator
Moderator
Moderator
250 solutions authored 10 likes given 500 replies posted

You can read the source code generated by CapSense_ADC component to make it clear, the conversion logic is defined in CapSese_ADC_Adc_INT.c , you can find below code in isr function  CY_ISR(CapSense_ADC_1_AdcIntrHandler)

/*******************************************************************************************/

    /* Read ADC result and check for ADC_ABORT or ADC_OVERFLOW flags */

    tmpResult = CY_GET_REG32(CapSense_ADC_1_ADC_RES_PTR);

    if (0uL == (tmpResult & CapSense_ADC_1_AdcADC_RES_ABORT_MASK))

    {

        if (0uL == (tmpResult & CapSense_ADC_1_AdcADC_RES_OVERFLOW_MASK))

        {

            /* Read ADC status, define polarity, value and ChId */

            adcFsmStatus = (uint8)(CapSense_ADC_1_dsRam.adcStatus & CapSense_ADC_1_AdcSTATUS_FSM_MASK);

            /* Select the polarity bit */

            polarity = tmpResult & CapSense_ADC_1_AdcADC_RES_HSCMPPOL_MASK;

            /* Select the result value */

            tmpResult &= CapSense_ADC_1_AdcADC_RES_VALUE_MASK;

            tmpChId = CapSense_ADC_1_dsRam.adcStatus & (uint8)(CapSense_ADC_1_AdcSTATUS_LASTCHAN_MASK);

           /* ADC could have been converting or calibrating; handle each differently. */

            switch (adcFsmStatus)

            {

            case CapSense_ADC_1_AdcSTATUS_CONVERTING:

                /*

                * After the converting will calculate an ADC result in mV depending on

                * sourcing or sinking mode. Checks for a saturation in all modes.

                */

                /* HSCMP polarity is 0:sink, 1:source */

                if(0uL != polarity) /* Sourcing */

                {

                   /* Saturate result at tVssa2Vref */

                    tmpResult = (tmpResult > (uint32)tVssa2Vref) ? (uint32)tVssa2Vref : tmpResult;

                    /* Scale result to Resolution range with rounding*/

                    tmpResult = ((((uint32)tVssa2Vref - tmpResult) * CapSense_ADC_1_AdcRES_MAX) +

                                 ((uint32)tFull >> 1uL)) / (uint32)tFull;

                }

                else /* Sinking */

                {

                    #if (CapSense_ADC_1_ADC_FULLRANGE_MODE == CapSense_ADC_1_ADC_MEASURE_MODE)

                        /* Scale result with sink/source mismatch with rounding */

                        tmpResult = (((uint32)((uint32)tRecover << 1u) * tmpResult) + ((uint32)tVssa2Vref >> 1u)) / (uint32)tVssa2Vref;

                        /* Saturate result at t_Vdda2Vref*/

                        tmpResult = (tmpResult > (uint32)tVdda2Vref) ? (uint32)tVdda2Vref : tmpResult;

                        /* Scale result to Resolution range with rounding */

                        tmpResult = ((((uint32)tVssa2Vref + tmpResult) * CapSense_ADC_1_AdcRES_MAX)  +

                                     ((uint32)tFull >> 1uL)) / (uint32)tFull;

                    #else /* (CapSense_ADC_1_ADC_FULLRANGE_MODE == CapSense_ADC_1_ADC_MEASURE_MODE) */

                        /* In vref mode, we are not supposed to be sinking. Saturate */

                        tmpResult = ((uint32)tVssa2Vref * CapSense_ADC_1_AdcRES_MAX) / (uint32)tFull;

                    #endif /* (CapSense_ADC_1_ADC_FULLRANGE_MODE == CapSense_ADC_1_ADC_MEASURE_MODE) */

                }

                /* Store ADC result code */

                CapSense_ADC_1_dsRam.adcCode [tmpChId] = (uint16)(tmpResult);

                /* Scale result to mV with rounding and store it */

                tmpResult = ((uint32)vMaxMv * tmpResult) / CapSense_ADC_1_AdcRES_MAX;

                CapSense_ADC_1_dsRam.adcResult[tmpChId] = (uint16)(tmpResult);

                CapSense_ADC_1_dsRam.adcStatus = CapSense_ADC_1_AdcSTATUS_IDLE;

                break;

.......

......

/*******************************************************************************************/

Please note that the formula include some static variables (tFull, tVssa2Vref, etc.), these variables store the calibration values measure by API CapSense_ADC_AdcCalibrate() which be called in CapSense_ADC_Start() once.

View solution in original post

0 Likes
1 Reply
Vison_Zhang
Moderator
Moderator
Moderator
250 solutions authored 10 likes given 500 replies posted

You can read the source code generated by CapSense_ADC component to make it clear, the conversion logic is defined in CapSese_ADC_Adc_INT.c , you can find below code in isr function  CY_ISR(CapSense_ADC_1_AdcIntrHandler)

/*******************************************************************************************/

    /* Read ADC result and check for ADC_ABORT or ADC_OVERFLOW flags */

    tmpResult = CY_GET_REG32(CapSense_ADC_1_ADC_RES_PTR);

    if (0uL == (tmpResult & CapSense_ADC_1_AdcADC_RES_ABORT_MASK))

    {

        if (0uL == (tmpResult & CapSense_ADC_1_AdcADC_RES_OVERFLOW_MASK))

        {

            /* Read ADC status, define polarity, value and ChId */

            adcFsmStatus = (uint8)(CapSense_ADC_1_dsRam.adcStatus & CapSense_ADC_1_AdcSTATUS_FSM_MASK);

            /* Select the polarity bit */

            polarity = tmpResult & CapSense_ADC_1_AdcADC_RES_HSCMPPOL_MASK;

            /* Select the result value */

            tmpResult &= CapSense_ADC_1_AdcADC_RES_VALUE_MASK;

            tmpChId = CapSense_ADC_1_dsRam.adcStatus & (uint8)(CapSense_ADC_1_AdcSTATUS_LASTCHAN_MASK);

           /* ADC could have been converting or calibrating; handle each differently. */

            switch (adcFsmStatus)

            {

            case CapSense_ADC_1_AdcSTATUS_CONVERTING:

                /*

                * After the converting will calculate an ADC result in mV depending on

                * sourcing or sinking mode. Checks for a saturation in all modes.

                */

                /* HSCMP polarity is 0:sink, 1:source */

                if(0uL != polarity) /* Sourcing */

                {

                   /* Saturate result at tVssa2Vref */

                    tmpResult = (tmpResult > (uint32)tVssa2Vref) ? (uint32)tVssa2Vref : tmpResult;

                    /* Scale result to Resolution range with rounding*/

                    tmpResult = ((((uint32)tVssa2Vref - tmpResult) * CapSense_ADC_1_AdcRES_MAX) +

                                 ((uint32)tFull >> 1uL)) / (uint32)tFull;

                }

                else /* Sinking */

                {

                    #if (CapSense_ADC_1_ADC_FULLRANGE_MODE == CapSense_ADC_1_ADC_MEASURE_MODE)

                        /* Scale result with sink/source mismatch with rounding */

                        tmpResult = (((uint32)((uint32)tRecover << 1u) * tmpResult) + ((uint32)tVssa2Vref >> 1u)) / (uint32)tVssa2Vref;

                        /* Saturate result at t_Vdda2Vref*/

                        tmpResult = (tmpResult > (uint32)tVdda2Vref) ? (uint32)tVdda2Vref : tmpResult;

                        /* Scale result to Resolution range with rounding */

                        tmpResult = ((((uint32)tVssa2Vref + tmpResult) * CapSense_ADC_1_AdcRES_MAX)  +

                                     ((uint32)tFull >> 1uL)) / (uint32)tFull;

                    #else /* (CapSense_ADC_1_ADC_FULLRANGE_MODE == CapSense_ADC_1_ADC_MEASURE_MODE) */

                        /* In vref mode, we are not supposed to be sinking. Saturate */

                        tmpResult = ((uint32)tVssa2Vref * CapSense_ADC_1_AdcRES_MAX) / (uint32)tFull;

                    #endif /* (CapSense_ADC_1_ADC_FULLRANGE_MODE == CapSense_ADC_1_ADC_MEASURE_MODE) */

                }

                /* Store ADC result code */

                CapSense_ADC_1_dsRam.adcCode [tmpChId] = (uint16)(tmpResult);

                /* Scale result to mV with rounding and store it */

                tmpResult = ((uint32)vMaxMv * tmpResult) / CapSense_ADC_1_AdcRES_MAX;

                CapSense_ADC_1_dsRam.adcResult[tmpChId] = (uint16)(tmpResult);

                CapSense_ADC_1_dsRam.adcStatus = CapSense_ADC_1_AdcSTATUS_IDLE;

                break;

.......

......

/*******************************************************************************************/

Please note that the formula include some static variables (tFull, tVssa2Vref, etc.), these variables store the calibration values measure by API CapSense_ADC_AdcCalibrate() which be called in CapSense_ADC_Start() once.

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