XIAO nRF52840 fast digitalRead?

Products & Technology XIAO
2

Try this.

void setup()
{
  Serial.begin(115200);
  while(!Serial);
  delay(1000);

  pinMode(P0_3, INPUT_PULLUP);  //D1(P0.03) connected SW
}

void loop()
{
  uint32_t REPEAT = 1000000;
  uint32_t timestamp = millis();
  int x;
  for(uint32_t i = 0; i < REPEAT; i++) {
    x = (nrf_gpio_port_in_read(NRF_P0) >> 3) & 1UL;
//    x = digitalRead(P0_3);
  }
  Serial.println(millis() - timestamp);
}