Sampling at 8 Khz

Hi , i’m using an DUE model and trying to sample data , using analogRead , at 8 Khz , as i read here , https://www.arduino.cc/en/Reference/AnalogRead , it takes 100 microseconds to read the port , i’ve added a 25 microsecond delay , and a led indicatior when my while loop is finished to sample , im sampling about 80,000 values , at 8 bit resolution .
this is my code :

yte arr[80000];
int ledPin = 22;
int sw = 24 ;
int i = 0 ;
int flag = 0 ;
int j = 0 ;
int Sw_state = 0;

void setup() {
// put your setup code here, to run once:
Serial1.begin(115200);
Serial.begin(115200);
pinMode(ledPin , OUTPUT);
pinMode(sw , INPUT);
}

void loop() {

if ( flag == 0 ) {
while ( i< 80000 ){
analogReadResolution( 8 );
arr = analogRead(A0);

  • delayMicroseconds(25); *

  • i++ ;*

  • if ( i== 80000 ) {*

  • flag = 1 ;*

  • }*

  • }*

  • }*

  • Sw_state = digitalRead(sw) ;*

  • if (flag == 1) {*

  • digitalWrite(ledPin , HIGH);*

  • }*

  • if ((flag == 1) && (Sw_state == 1)) {*

  • digitalWrite(ledPin,LOW);*

  • while ( j < 80000 ) {*

  • Serial1.write(arr[j]) ;*

  • j++ ;*

  • if (j == 80000 ){ *

  • flag = 2 ;*

  • }*

  • }*

  • }*

}
*the problem is , that the led turns on immediately after flashing is done , and not after 10 seconds as expected. what do you think guys , what is wrong with my code ? *

Try initializing the pin LOW in setup().