1.22.1 Analog to Digital Converter (ADCHS)

  • 12-bit Analog to Digital Converter

  • 18 Msps with up to six ADC circuits (five dedicated and one shared)

  • Up to 45 analog input

  • Can operate during Sleep and Idle modes

  • Multiple trigger sources

  • Six Digital Comparators and six Digital Filters

Using The Library

Interrupt mode:

#include <stddef.h>                     // Defines NULL
#include <stdbool.h>                    // Defines true
#include <stdlib.h>                     // Defines EXIT_FAILURE
#include "definitions.h"                // SYS function prototypes

#define ADC_VREF                (3.3f)
#define ADC_MAX_COUNT           (4095)

uint16_t adc_count;
float input_voltage;
volatile bool result_ready = false;

// *****************************************************************************
// *****************************************************************************
// Section: Main Entry Point
// *****************************************************************************
// *****************************************************************************

void ADC_ResultHandler(ADCHS_CHANNEL_NUM channel, uintptr_t context)
{
    /* Read the ADC result */
    adc_count = ADCHS_ChannelResultGet(ADCHS_CH3);    
    result_ready = true;
}


int main ( void )
{
    /* Initialize all modules */
    SYS_Initialize ( NULL );
    
    printf("\n\r---------------------------------------------------------");
    printf("\n\r                    ADC Interrupt Mode Demo                 ");
    printf("\n\r---------------------------------------------------------\n\r"); 
    
    ADCHS_CallbackRegister(ADCHS_CH3, ADC_ResultHandler, (uintptr_t)NULL);
    TMR3_Start();
    
    while ( true )
    {
        /* Maintain state machines of all polled MPLAB Harmony modules. */
        SYS_Tasks ( );
        
        /* Wait till ADC conversion result is available */
        if (result_ready == true)
        {
            result_ready = false;
            input_voltage = (float)adc_count * ADC_VREF / ADC_MAX_COUNT;

            printf("ADC Count = 0x%03x, ADC Input Voltage = %d.%02d V \r", adc_count, (int)input_voltage, (int)((input_voltage - (int)input_voltage)*100.0));        
        }
    }

    /* Execution should not come here during normal operation */

    return ( EXIT_FAILURE );
}

Polling mode:

#include <stddef.h>                     // Defines NULL
#include <stdbool.h>                    // Defines true
#include <stdlib.h>                     // Defines EXIT_FAILURE
#include "definitions.h"                // SYS function prototypes

#define ADC_VREF                (3.3f)
#define ADC_MAX_COUNT           (4095)

uint16_t adc_count;
float input_voltage;

// *****************************************************************************
// *****************************************************************************
// Section: Main Entry Point
// *****************************************************************************
// *****************************************************************************

int main ( void )
{
    /* Initialize all modules */
    SYS_Initialize ( NULL );
    
    printf("\n\r---------------------------------------------------------");
    printf("\n\r                    ADC Polled Mode Demo                 ");
    printf("\n\r---------------------------------------------------------\n\r"); 
    
    TMR3_Start();
    
    while ( true )
    {
        /* Maintain state machines of all polled MPLAB Harmony modules. */
        SYS_Tasks ( );
        
        /* Wait till ADC conversion result is available */
        while(!ADCHS_ChannelResultIsReady(ADCHS_CH3))
        {

        };

        /* Read the ADC result */
        adc_count = ADCHS_ChannelResultGet(ADCHS_CH3);
        input_voltage = (float)adc_count * ADC_VREF / ADC_MAX_COUNT;

        printf("ADC Count = 0x%03x, ADC Input Voltage = %d.%02d V \r", adc_count, (int)input_voltage, (int)((input_voltage - (int)input_voltage)*100.0));        
    }

    /* Execution should not come here during normal operation */

    return ( EXIT_FAILURE );
}

Library Interface

12-bit Analog to Digital Converter peripheral library provides the following interfaces:

Functions

Name Description
ADCHS_Initialize Initializes given instance of ADCHS peripheral
ADCHS_ModulesEnable Enables the ADC modules
ADCHS_ModulesDisable Disables the ADC modules
ADCHS_ChannelResultInterruptEnable Enables the ADC channel result data interrupt
ADCHS_ChannelResultInterruptDisable Disables the ADC channel result data interrupt
ADCHS_ChannelEarlyInterruptEnable Enables the ADC channel early result data interrupt
ADCHS_ChannelEarlyInterruptDisable Disables the ADC channel early result data interrupt
ADCHS_ChannelConversionStart Starts the ADC conversion of an analog channel
ADCHS_GlobalEdgeConversionStart Starts the ADC conversion of analog channels configured for global software edge trigger
ADCHS_GlobalLevelConversionStart Starts the ADC conversion of analog channels configured for global software level trigger
ADCHS_GlobalLevelConversionStop Stops the global software level trigger
ADCHS_ChannelResultIsReady Returns the status of the channel conversion
ADCHS_EOSStatusGet Returns the status of the end of scan interrupt flag
ADCHS_ChannelResultGet Reads the conversion result of the channel
ADCHS_CallbackRegister Registers the function to be called from interrupt
ADCHS_EOSCallbackRegister Registers the function to be called from end of scan interrupt
ADCHS_DMASampleCountBaseAddrSet Registers the user-defined RAM address at which the DMA engine will start saving the current count of output samples
ADCHS_DMAResultBaseAddrSet Registers the user-defined RAM address at which the DMA engine will start saving the converted data
ADCHS_DMACallbackRegister Registers the application event handler which is called when the DMA transfer is complete
ADCHS_DMAStatusGet Returns the DMA transfer status
ADCHS_ComparatorxEnable Enables comparator
ADCHS_ComparatorxDisable Disables comparator
ADCHS_ComparatorxLimitSet Sets lower and higher threshold for comparator
ADCHS_ComparatorxEventModeSet Sets the condition under which the comparator output becomes true
ADCHS_ComparatorxAnalogInputIDGet Identifies the analog input for which the comparator event is generated
ADCHS_ComparatorxCallbackRegister Registers the function to be called from the ADC comparator interrupt
ADCHS_ComparatorxStatusGet Returns the Comparator status
ADCHS_FilterxIsReady Returns the status of ADC filter
ADCHS_FilterxDataGet Returns the ADC filter data
ADCHS_FilterxCallbackRegister Registers the function to be called from the ADC filter ready interrupt

Data types and constants

Name Type Description
ADCHS_MODULE_MASK Enum Identifies dedicated and shared ADC module mask
ADCHS_CHANNEL_NUM Enum Identifies ADCHS inputs as analog channel number
ADCHS_CMP_EVENT_MODE Enum Identifies ADCHS comparator event modes
ADCHS_DMA_STATUS Enum Identifies ADCHS DMA status
ADCHS_CALLBACK Typedef Defines the function pointer data type and function signature for the adchs peripheral callback function
ADCHS_DC_CALLBACK Typedef Defines the function pointer data type and function signature for the adchs digital comparator interrupt callback function
ADCHS_DF_CALLBACK Typedef Defines the function pointer data type and function signature for the adchs digital filter interrupt callback function
ADCHS_DMA_CALLBACK Typedef Defines the function pointer data type and function signature for the adchs DMA interrupt callback function
ADCHS_EOS_CALLBACK Typedef Defines the function pointer data type and function signature for the adchs end of scan interrupt callback function
ADCHS_CALLBACK_OBJECT Struct ADCHS Callback structure
ADCHS_EOS_CALLBACK_OBJECT Struct ADCHS Callback structure for End of Scan (EOS) interrupt