Onboard LED

Overview

The onboard LED is wired to a dedicated GPIO on every Core, known from the Core definition, so there’s no pad to assign. core_init() doesn’t set it up: call core_led_init() once after it. How you drive it depends on the layer:

Core — header-only helpers (core_led_*): on / off / toggle plus blink and heartbeat patterns. The everyday path, and what Studio emits.

It’s also the SDK’s failure indicator: the fault handler blinks SOS on it.

On, off, toggle

The direct controls. toggle is non-blocking — good from an event handler that already fires at the rate you want:

#include "core.h"

  core_init();
  core_led_init();     // once: LED pin as a push-pull output, off

  core_led_on();       // light it
  core_led_off();      // and off
  core_led_toggle();   // flip — no delay

Patterns

Two timed helpers. core_led_blink blinks a fixed number of times and blocks. core_led_heartbeat(period_ms, on_ms) is set up once and then runs by itself from the 1 ms SysTick, so the loop stays free. Calling it again restarts the cycle, so don’t call it on every pass:

core_led_blink(3, 100, 100);   // 3 quick blinks, then return
  core_led_heartbeat(1000, 2);   // a 2 ms blip every second, from SysTick

  while (1) {
      core_watchdog_feed();      // core_watchdog.h; the templates arm a 5 s watchdog
      do_work();
  }

A short on_ms keeps the same brightness across the supply: on the L0, L4 and W5 it is lengthened as VDD drops (a 2 ms blip at 3.3 V is about 32 ms at 1.8 V). period_ms = 0 stops it.

Cross-architecture support

The onboard LED is part of every Core’s baseline (and its GPIO underpinning is verified everywhere):

See the implementation status for the full matrix.

Known gaps

What the SDK itself lists as missing here, straight from the header:

API reference

void core_led_on(void);

void core_led_off(void);

void core_led_toggle(void);

void core_led_blink(int n, int on_ms, int off_ms);

void core_led_heartbeat(int period_ms, int on_ms);

void core_led_init(void);

void core_led_sos(void);