// The software meander 2
// having the variable frequency from 1 ms to 1 s
// with the step 1 ms.
// The waves package is changing
// from 1 KHz to 1 Hz and back.

int led = 13; // pin LED
int ms = 1000; // max delay

void setup() {
 pinMode(led, OUTPUT);
}

void loop() {
 for (int i = 0; i <= ms; i++) { // up
  ledPulse(i);
 }
 for (int i = ms; i >= 0; i--) { // down
  ledPulse(i);
 }
}

void ledPulse(int j) {
 
 digitalWrite(led, HIGH);
 delay(j);
 digitalWrite(led, LOW);
 delay(j);
}