2.5 Analog Front-End Controller (AFEC)

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

/*****************************************************
 AFEC CH0 - PB01 - Connect to DACC output PB13
 AFEC CH5 - PC30 - connect to Vcc
 AFEC_CH6 - PC31 - Connect to GND
 *****************************************************/

#define AFEC_VREF               (3.3f)
#define DAC_COUNT_INCREMENT     (124U)  // Equivalent to 0.1V 
#define DAC_COUNT_MAX           (4095U)


volatile uint16_t adc_ch0_count, adc_ch5_count, adc_ch6_count;

float adc_ch0_voltage, adc_ch5_voltage, adc_ch6_voltage;

volatile bool result_ready;
/* Initial DAC count which is midpoint = 1.65V*/
uint16_t dac_count=0x800; 


void switch_handler( PIO_PIN pin, uintptr_t context )
{
    /* Write next data sample */
    dac_count = dac_count + DAC_COUNT_INCREMENT;
    
    if (dac_count > DAC_COUNT_MAX)
            dac_count=0;    
    
    DACC_DataWrite(DACC_CHANNEL_0, dac_count);
}

/* This function is called after conversion of last channel in the user sequence */
void AFEC_EventHandler(uint32_t status, uintptr_t context)
{
    /* Read the result of 3 channels*/
    adc_ch5_count = AFEC1_ChannelResultGet(CH5_VDD);
    adc_ch6_count = AFEC1_ChannelResultGet(CH6_GND);
    adc_ch0_count = AFEC1_ChannelResultGet(CH0_SINE_WAVE);
       
    result_ready = true;

}

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

int main ( void )
{
    /* Initialize all modules */
    SYS_Initialize ( NULL );
    
    PIO_PinInterruptCallbackRegister(SWITCH_PIN, &switch_handler, (uintptr_t) NULL );
    PIO_PinInterruptEnable(SWITCH_PIN);

    /* Register callback function for AFEC end of conversion interrupt*/
    AFEC1_CallbackRegister(AFEC_EventHandler, (uintptr_t)NULL);
    
    /* Write first data sample in DAC channel 0 and channel 1*/
    DACC_DataWrite(DACC_CHANNEL_0, dac_count);
    
    /* Start the timer to trigger ADC conversion every 50 ms*/
    TC1_CH0_CompareStart();

    printf("\n\r---------------------------------------------------------");
    printf("\n\r                    AFEC User Sequence Demo                 ");
    printf("\n\r---------------------------------------------------------\n\r");
    printf("CH0 Count  CH0 Voltage  CH5 Count  CH5 Voltage  CH6 Count  CH6 Voltage \n\r");           

    while ( true )
    {
        /* Check if result is ready to be transmitted to console */
        if (result_ready == true)
        {
            adc_ch5_voltage = (float)adc_ch5_count * AFEC_VREF/4095U;
            adc_ch6_voltage = (float)adc_ch6_count * AFEC_VREF/4095U;
            adc_ch0_voltage = (float)adc_ch0_count * AFEC_VREF/4095U;
            printf("0x%03x      %0.2f V       0x%03x      %0.2f V       0x%03x      %0.2f V \t\r", \
                    adc_ch0_count, adc_ch0_voltage, adc_ch5_count, adc_ch5_voltage, adc_ch6_count, adc_ch6_voltage);
                           
                
            result_ready = false;
        }
    }

    /* 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 <stdio.h>
#include "definitions.h"                // SYS function prototypes

#define AFEC_VREF               (3.3f)
#define DAC_COUNT_INCREMENT     (124U)  // equivalent to 0.1V 
#define DAC_COUNT_MAX           (4095U)

uint16_t adc_count;
float input_voltage;
/* Initial value of dac count which is midpoint = 1.65 V*/
uint16_t dac_count = 0x800;   


void switch_handler( PIO_PIN pin, uintptr_t context )
{
    /* Write next data sample */
    dac_count = dac_count + DAC_COUNT_INCREMENT;
    
    if (dac_count > DAC_COUNT_MAX)
            dac_count=0;    
    
    DACC_DataWrite(DACC_CHANNEL_0, dac_count);
}

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

int main ( void )
{
    /* Initialize all modules */
    SYS_Initialize ( NULL );
    
    PIO_PinInterruptCallbackRegister(SWITCH_PIN, &switch_handler, (uintptr_t) NULL );
    PIO_PinInterruptEnable(SWITCH_PIN);
    
    printf("\n\r---------------------------------------------------------");
    printf("\n\r                    AFEC Demo                 ");
    printf("\n\r---------------------------------------------------------\n\r");
    printf("Press switch to change the DAC output. \r\n");
    
    SYSTICK_TimerStart();

    DACC_DataWrite(DACC_CHANNEL_0, dac_count);
        
    while (1)
    {
        /* Start ADC conversion */
        AFEC1_ConversionStart();

        /* Wait till ADC conversion result is available */
        while(!AFEC1_ChannelResultIsReady(AFEC_CH0))
        {

        };

        /* Read the ADC result */
        adc_count = AFEC1_ChannelResultGet(AFEC_CH0);
        input_voltage = (float)adc_count * AFEC_VREF / 4095U;

        printf("ADC Count = 0x%03x, ADC Input Voltage = %0.2f V \r",adc_count, input_voltage);    
        
        SYSTICK_DelayMs(500);
    }
    
    /* Execution should not come here during normal operation */

    return ( EXIT_FAILURE );
}

Library Interface

Analog Front-End Controller peripheral library provides the following interfaces:

Functions

Data types and constants