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PSoC 6 MCU

EuGe_296116
Contributor II

I have a project with an ADC wired as follows:

pastedImage_1.png

and configured as follows:

pastedImage_0.png

VDDA is 3.3V.  When I feed a voltage of 2.00V into VBatIn, I get a result of approximately 430 counts, which comes out to approximately 1.4V.  The behaviour is the same if I buffer the signal internally with an Opamp component.

Is something misconfigured here?  What do I need to do to get the right values coming out of the ADC?

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1 Solution
MotooTanaka
Esteemed Contributor

Hi,

Have you tried to use ADC_CountsTo_mVolts() function?

I tried the following using CY8CKIT-062-WIFI-BT (CY8C6247BZI-D54ES on board)

(1) Schematic

000-schematic.JPG

(2) ADC Config

Note: Although I tried to duplicate your config, I noticed that the "Scan duration" is quite different from yours.

002-ADC-Config.JPG

(3) Pin assign

001-pin-assign.JPG

(4) main.c

====================

#include "project.h"

#include "stdio.h"

#define STR_LEN 128

char str[STR_LEN+1] ;

void print(char *str)

{

    UART_PutString(str) ;

}

void init_hardware(void)

{

    __enable_irq() ;

    UART_Start() ;

    ADC_Start() ;

}

void splash(void)

{

    snprintf(str, STR_LEN, "PSoC 6 ADC Test (%s %s)\n", __DATE__, __TIME__) ;

    print(str) ;

}

void measure(void)

{

    int16_t adc_count ;

    int16_t mV ;

    ADC_StartConvert() ;

    ADC_IsEndConversion(CY_SAR_WAIT_FOR_RESULT) ;

    adc_count = ADC_GetResult16(0) ;

    mV = ADC_CountsTo_mVolts(0, adc_count) ;

    snprintf(str, STR_LEN, "%5d mV : %4d\n", mV, adc_count) ;

    print(str) ;

    return ;

}

int main(void)

{

    init_hardware() ;

//    __enable_irq(); /* Enable global interrupts. */

//    /* Enable CM4.  CY_CORTEX_M4_APPL_ADDR must be updated if CM4 memory layout is changed. */

//    Cy_SysEnableCM4(CY_CORTEX_M4_APPL_ADDR);  /* this time I use only CM0+ */

    splash() ;

    for(;;)

    {

        measure() ;

        CyDelay(1000) ;

    }

}

====================

(5) Tera Term output

003-TeraTerm-log.JPG

(6) I connected 3.3V, GND, and A0 (P10[0]) from the board to a POT (10K)

At 0.000V (~ -0.000V): program reported -2mV ~ 3mV, adc_count -1 ~ 2

0V.JPG

At 1.001V program reported 1014 mV ~ 1022 mV, adc_count 629 ~ 632

1V.JPG

At 2.007V program reported 2037 mV ~ 2045 mV, adc_count 1264 ~ 1269

2V.JPG

At 3.006V program reported 3055 mV ~ 3060 mV, adc_count 1896 ~ 1899

3V.JPG

So IMHO, the voltage reported via ADC_CountsTo_mVolts() seems to be reasonable for my hardware setup.

You may want to take a look at inside this function to confirm how they convert ADC count to mV.

moto

View solution in original post

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2 Replies
EuGe_296116
Contributor II

When can I expect a Cypress response to this question?  Is there another support avenue where I could get responses more reliably?

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MotooTanaka
Esteemed Contributor

Hi,

Have you tried to use ADC_CountsTo_mVolts() function?

I tried the following using CY8CKIT-062-WIFI-BT (CY8C6247BZI-D54ES on board)

(1) Schematic

000-schematic.JPG

(2) ADC Config

Note: Although I tried to duplicate your config, I noticed that the "Scan duration" is quite different from yours.

002-ADC-Config.JPG

(3) Pin assign

001-pin-assign.JPG

(4) main.c

====================

#include "project.h"

#include "stdio.h"

#define STR_LEN 128

char str[STR_LEN+1] ;

void print(char *str)

{

    UART_PutString(str) ;

}

void init_hardware(void)

{

    __enable_irq() ;

    UART_Start() ;

    ADC_Start() ;

}

void splash(void)

{

    snprintf(str, STR_LEN, "PSoC 6 ADC Test (%s %s)\n", __DATE__, __TIME__) ;

    print(str) ;

}

void measure(void)

{

    int16_t adc_count ;

    int16_t mV ;

    ADC_StartConvert() ;

    ADC_IsEndConversion(CY_SAR_WAIT_FOR_RESULT) ;

    adc_count = ADC_GetResult16(0) ;

    mV = ADC_CountsTo_mVolts(0, adc_count) ;

    snprintf(str, STR_LEN, "%5d mV : %4d\n", mV, adc_count) ;

    print(str) ;

    return ;

}

int main(void)

{

    init_hardware() ;

//    __enable_irq(); /* Enable global interrupts. */

//    /* Enable CM4.  CY_CORTEX_M4_APPL_ADDR must be updated if CM4 memory layout is changed. */

//    Cy_SysEnableCM4(CY_CORTEX_M4_APPL_ADDR);  /* this time I use only CM0+ */

    splash() ;

    for(;;)

    {

        measure() ;

        CyDelay(1000) ;

    }

}

====================

(5) Tera Term output

003-TeraTerm-log.JPG

(6) I connected 3.3V, GND, and A0 (P10[0]) from the board to a POT (10K)

At 0.000V (~ -0.000V): program reported -2mV ~ 3mV, adc_count -1 ~ 2

0V.JPG

At 1.001V program reported 1014 mV ~ 1022 mV, adc_count 629 ~ 632

1V.JPG

At 2.007V program reported 2037 mV ~ 2045 mV, adc_count 1264 ~ 1269

2V.JPG

At 3.006V program reported 3055 mV ~ 3060 mV, adc_count 1896 ~ 1899

3V.JPG

So IMHO, the voltage reported via ADC_CountsTo_mVolts() seems to be reasonable for my hardware setup.

You may want to take a look at inside this function to confirm how they convert ADC count to mV.

moto

View solution in original post

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