// for https://forum.arduino.cc/t/generating-pwm-square-wave-output/1120387/4

void setup() {
  // Pins D9 and D10 - 244 Hz 10bit
  TCCR1A = 0b00000011; // 10bit
  TCCR1B = 0b00001011; // x64 fast pwm
  analogWrite(10, 511); // range 0-1023
}

void loop() {
}