Raspberry Pi ADC Interrupt

#include <stdio.h>

#include <string.h>

#include <errno.h>

#include <stdlib.h>

#include <wiringPi.h>

#include <wiringPiSPI.h>

#define CS_MCP3208  8       // BCM_GPIO8

#define BUTTON_PIN 3

#define DG_OUT 7

#define CHANNEL_BIT_MASK 0x07

#define BYTE_I_MASK 0x06

#define BYTE_II_MASK 0x00

#define BYTE_II_RCV_MASK 0x0F

#define SPI_CHANNEL 0

#define SPI_SPEED   2000000 // !! Start low here and if all works try to increase if needed on a breadboard I could go upto about 750000 

int toggle = 1;

int start, end;

int read_mcp3208_adc(unsigned char adcChannel);

void myInterrupt(void) {

  int adc1Channel = 0;

  int adc1Value   = 0;

  start = micros();

  toggle ^= 1;

  digitalWrite(DG_OUT, toggle); 

  adc1Value = read_mcp3208_adc(adc1Channel);

  adc1Value = (3.3/4096) * adc1Value;

  end = micros();

  //printf("\n int: 0 %d \n", end - start);

}

int main (void)

{

  //int adc1Channel = 0;

  //int adc1Value   = 0;

  if(wiringPiSetup() == -1)

  {

    fprintf (stdout, "Unable to start wiringPi: %s\n", strerror(errno));

    return 1 ;

  }

  wiringPiSPISetup(SPI_CHANNEL, SPI_SPEED);

    if ( wiringPiISR (BUTTON_PIN, INT_EDGE_RISING, &myInterrupt) < 0 ) {

      fprintf (stderr, "Unable to setup ISR: %s\n", strerror (errno));

      return 1;

  }

  pinMode(CS_MCP3208, OUTPUT);

  pinMode(DG_OUT, OUTPUT);

  while(1)

  {

    //system("clear");

    //printf("\n\nMCP3208 channel output.\n\n");

    //adc1Value = read_mcp3208_adc(adc1Channel);

    //printf("adc0 Value = %04u", adc1Value);

    //printf("\tVoltage = %.6f\n", ((3.3/4096) * adc1Value));

    usleep(1000000);

    //printf("\n int: 0 %d \n", end - start);

    //waitForInterrupt(BUTTON_PIN,1);

  }

  return 0;

}

int read_mcp3208_adc(unsigned char adcChannel)

{

  unsigned char buff[3];

  int adcValue = 0;

  buff[0] = BYTE_I_MASK | ((adcChannel & CHANNEL_BIT_MASK) >> 2);

  buff[1] = ((adcChannel & CHANNEL_BIT_MASK) << 6);

  buff[2] = BYTE_II_MASK;

  digitalWrite(CS_MCP3208, 0);  // Low : CS Active

  wiringPiSPIDataRW(SPI_CHANNEL, buff, 3);

  buff[1] = BYTE_II_RCV_MASK & buff[1];

  adcValue = ( buff[1] << 8) | buff[2];

  digitalWrite(CS_MCP3208, 1);  // High : CS Inactive

  return adcValue;

}