#include <SPI.h>
#include <SD.h>
File myFile;
volatile float time = 0;
int num = 1;
#define pot A0
#define timestamp 1000.0    // make it as you like
#define timeinseconds timestamp/1000.0
#define TimeBeforeReading (10.0-1.0)*timeinseconds
uint16_t p , n;
volatile bool printed = 0;
void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }


  Serial.println("Initializing SD card...");

  if (!SD.begin(10)) {
    Serial.println("initialization failed!");
    while (1);
  }
  Serial.println("initialization done.");

  // open the file. note that only one file can be open at a time,
  // so you have to close this one before opening another.

p = millis();
}

void WriteinFile(String filename, int data)
{
  myFile = SD.open(filename, FILE_WRITE);
  if (myFile) {
    printed = 0;
      Serial.println("Writing to test.txt...");
      myFile.print(num);
      myFile.print(".   ");
      myFile.println(data);
      num++;
    } else {
      // if the file didn't open, print an error:
      Serial.println("error opening test.txt");
    }
 
 myFile.close();


}

void loop() {
  // put your main code here, to run repeatedly:

 
  if (millis() - p > timestamp && time <= TimeBeforeReading)
  {
    WriteinFile("test.txt", analogRead(pot));
    p = millis();
    time+=timeinseconds;
  }
  if( time > TimeBeforeReading && printed == 0)
  {
  printed = 1;
     //reading the data... 
   myFile = SD.open("test.txt");
  if (myFile) {
    Serial.println("test.txt:");

    // read from the file until there's nothing else in it:
    while (myFile.available()) {
      Serial.write(myFile.read());
    }
    // close the file:
    myFile.close();
  } else {
    // if the file didn't open, print an error:
    Serial.println("error opening test.txt");
  
  }
  time = 0 ; 
  }
}