なにもしないスケッチ

int ledPin = 13;
int val = 0;
void setup()
{
 pinMode(ledPin, OUTPUT);
}

#define HALF 2000
void loop()
{
 val += 1;
 if((HALF+HALF)<val){ val = 0; };
 int v = val<HALF ? val : (HALF+HALF-val);
 digitalWrite(ledPin, HIGH);
 delayMicroseconds(v+1);
 digitalWrite(ledPin, LOW);
 delayMicroseconds(HALF-v+1);
}