15.5.3 Windowed Multiple Conversions

Windowed Conversions Example

#include <xc.h>
// The channel output from primary accumulator.
volatile long result = 0;
// The number of accumulated samples.
volatile long number_of_accumulated_samples;
int main()
{
    // RA4/RP5 pin is a trigger input.
    // Switch to a digital input.
    ANSELAbits.ANSELA4 = 0;
    // Make an input. 
    TRISAbits.TRISA4 = 1;
    // Map external pin trigger to RP5/RA4.
    _ADTRIG31R = 5; 
    // In this example channel 3 will be used.
    // Set limit for the accumulated samples number.
    AD1CH3CNTbits.CNT = 0xffff; 
    // Window conversion mode.
    AD1CH3CONbits.MODE = 1;
    // Accumulation will be started/stopped from an external pin.
    AD1CH3CONbits.TRG1SRC = 31; 
    // Trigger all conversions from the ADC repeat timer.
    AD1CH3CONbits.TRG2SRC = 3; 
    // Select the AN5 analog positive input/pin.
    AD1CH3CONbits.PINSEL = 5;
    // Select signal sampling time (6.5 TADs = 81nS).
    AD1CH3CONbits.SAMC = 3;
    // Set period of the triggers timer (63 is maximum).
    AD1CONbits.RPTCNT = 60;
    // Set ADC to RUN mode.
    AD1CONbits.MODE = 2;
    // Enable ADC.
    AD1CONbits.ON = 1;
    // Wait when ADC will be ready/calibrated.
    while(AD1CONbits.ADRDY == 0);
    // Enable interrupt;
    _AD1CH3IE = 1;
    
    // Channel 3 is converted and results are accumulated until the RA4 pin is high.
    // On transition from high to low an interrupt is generated.
    while(1);
    
    return 1;
}

void __attribute__((interrupt)) _AD1CH3Interrupt() {
    // Read result in accumulator and clear CH3RDY flag.
    result = AD1CH3DATA;
    number_of_accumulated_samples = AD1CH3CNTbits.CNTSTAT;
    result /= number_of_accumulated_samples;
    // Clear interrupt flag.
    _AD1CH3IF = 0;
}