// produce blocks of 16ns
// Inspired from: https://academy.cba.mit.edu/classes/input_devices/step/hello.txrx2.RP2040.ino
const int pin = 13; // Replace with your pin number
#define digitalWriteFast(pin,val) (val ? sio_hw->gpio_set = (1 << pin) : sio_hw->gpio_clr = (1 << pin))
#define digitalReadFast(pin) ((1 << pin) & sio_hw->gpio_in)

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

void loop() {
    digitalWriteFast(pin, HIGH);
    digitalWriteFast(pin, LOW);
    digitalWriteFast(pin, HIGH);
    digitalWriteFast(pin, LOW);
    digitalWriteFast(pin, HIGH);
    digitalWriteFast(pin, LOW);
    digitalWriteFast(pin, HIGH);
    digitalWriteFast(pin, LOW);
    digitalWriteFast(pin, HIGH);
    digitalWriteFast(pin, LOW);
    digitalWriteFast(pin, HIGH);
    digitalWriteFast(pin, LOW);
    digitalWriteFast(pin, HIGH);
    digitalWriteFast(pin, LOW);
    digitalWriteFast(pin, HIGH);
    digitalWriteFast(pin, LOW);
    digitalWriteFast(pin, HIGH);
    digitalWriteFast(pin, LOW);
    digitalWriteFast(pin, HIGH);
    digitalWriteFast(pin, LOW);
}