PORTB, 3 flashes at startup

Hi,

on my ATSAMD21G18A "PORTB, 3" flashes at startup.

Can I disable that somehow?

My test code is

void setup()
{
  digitalWrite(30, LOW);
  pinMode(30, OUTPUT);
}
void loop() {}

variant.cpp

  // 30..31 - RX/TX LEDS (PB03/PA27)
  // --------------------
  { PORTB,  3, PIO_OUTPUT, PIN_ATTR_DIGITAL, No_ADC_Channel, NOT_ON_PWM, NOT_ON_TIMER, EXTERNAL_INT_NONE }, // used as output only

OK, solved that flashing issue maybe. Mapped in variant.h #define PIN_LED_TXL to an unused pin

A remaining question is if PortA13 has interrupt capabilities? As far as I understood according variant.cpp it should be possible?

{ PORTA, 13, PIO_PWM, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM), No_ADC_Channel, PWM0_CH5, TCC0_CH0, EXTERNAL_INT_13 },

Hi timtailors,

A remaining question is if PortA13 has interrupt capabilities? As far as I understood according variant.cpp it should be possible?

All IO pins (both analog and digital) on the SAMD21 have standard interrupt capability with the exception of port pin PA08, which is the non maskable interrrupt (NMI).

Hi, thanks! Does the "standard" also include waking up the device from sleep or is there a kind of "extended" capability necessarily?

Does the "standard" also include waking up the device from sleep or is there a kind of "extended" capability necessarily?

Yes, each interrupt pin has a wake up capability. The Arduino attachInterrupt() function activates the wake up option by default.