LED_BUILTIN ? How to access

Community
#1

Where is it ? I see examples that use it but it doesn’t work on mi Xiao. Compiles OK but no flash. I see variant.h files that say 15, 13 & 6 but none flash the onboard LED. It does flash during loading & execution bur not under my control. Inquiring minds want to know.

#2

The basic (been around forever) Arduino “Blink” example works for me with the XIAO. Could you, perhaps, show us your complete sketch?

I note that LED_BUILTIN for the Seeeduino XIAO is Arduino pin 13, which is connected to the Yellow LED.
.
I modified the “Blink” sketch a little to illustrate the active-low operation of the built-in LED.
If the sketch compiles and uploads OK but the Yellow LED doesn’t give a brief flash every second, your XIAO is defective.

/*
 * Modification of the been-around-forever Arduino "Blink" example
 * for boards like the Seeeduino XIAO, which have an active-low LED
 * connection.
 * 
 * Changed so that on-time is different from off-time so that the
 * active-low operation can be observed.
 * 
 * davekw7x
 * July, 2022
 */

// Active-low LED connection
#define LED_ON  LOW
#define LED_OFF HIGH

// The LED will flash briefly every second
#define ON_TIME 100
#define OFF_TIME 900

// For the XIAO, LED_BUILTIN is Arduino pin 13, which is connected
// to the Yellow LED
//
// You can change the following statement to another pin if you want
// to experiment.
//
int led = LED_BUILTIN; // Yellow LED
//int led = PIN_LED2;  // Blue LED
//int led = PIN_LED3;  // Another Blue LED (Really???)

void setup()
{
  pinMode(led, OUTPUT);
} // End of setup()

void loop()
{
  digitalWrite(led, LED_ON);  // Turn the LED on by making the voltage LOW
  delay(ON_TIME);             // Wait for a tenth of a second.
  
  digitalWrite(led, LED_OFF); // Turn the LED off by making the voltage high
  delay(OFF_TIME);            // Wait for a second or so
} // End of loop()

Regards,

Dave

#3

Dave
OK solved, tried another XIAO, original has problems with its yellow/orange LED. Turns out there are at least 4 LEDs, clues are in your comments. I hadn’t seen PIN_LED2/3 called out anywhere before.

int led = LED_BUILTIN; // Yellow LED – orange on miine
int led = PIN_LED2; // Blue LED – yes
int led = PIN_LED3; // Another Blue LED (Really???) – yes
also a green one that seems on all the time, power ?

Thank you
PS, trying to write to pin 15 caused a condition where I needed a double reset to get the USB port back,