不用 delay 同时做两件事：让按钮和闪灯一起工作

// SPDX-License-Identifier: MIT
#include <Arduino.h>
constexpr uint8_t LED_PIN = 4, BUTTON_PIN = 5;
constexpr uint32_t DEBOUNCE_MS = 30;
bool candidate, stable, led = false;
uint32_t changedAt = 0, lastBlink = 0, intervalMs = 500, pressCount = 0;
uint32_t lastLoop = 0, maxLoopGap = 0, reportAt = 0;
bool due(uint32_t now, uint32_t then, uint32_t interval) {
  return uint32_t(now - then) >= interval;
}
void setup() {
  Serial.begin(115200);
  pinMode(LED_PIN, OUTPUT);
  digitalWrite(LED_PIN, LOW);
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  candidate = stable = digitalRead(BUTTON_PIN);
  changedAt = lastBlink = lastLoop = reportAt = millis();
  // No 49-day wait: unsigned arithmetic is checked with synthetic timestamps.
  const uint32_t before = 0xFFFFFFF0u, after = 0x00000020u;
  Serial.printf("wrap delta=%lu threshold47=%u threshold49=%u\n",
    (unsigned long)(after - before), due(after, before, 47), due(after, before, 49));
}
void loop() {
  const uint32_t now = millis();
  const uint32_t gap = now - lastLoop;
  lastLoop = now;
  if (gap > maxLoopGap) maxLoopGap = gap;
  const bool raw = digitalRead(BUTTON_PIN);
  if (raw != candidate) { candidate = raw; changedAt = now; }
  if (candidate != stable && due(now, changedAt, DEBOUNCE_MS)) {
    stable = candidate;
    if (stable == LOW) {
      intervalMs = intervalMs == 500 ? 150 : 500;
      Serial.printf("press=%lu accepted=%lu candidate=%lu debounce=%lu interval=%lu\n",
        (unsigned long)++pressCount, (unsigned long)now, (unsigned long)changedAt,
        (unsigned long)(now - changedAt), (unsigned long)intervalMs);
    }
  }
  if (due(now, lastBlink, intervalMs)) {
    lastBlink = now;  // skip missed edges rather than burst after a stall
    led = !led;
    digitalWrite(LED_PIN, led ? HIGH : LOW);
  }
  if (due(now, reportAt, 5000)) {
    reportAt = now;
    Serial.printf("max_loop_gap_ms=%lu interval=%lu\n",
      (unsigned long)maxLoopGap, (unsigned long)intervalMs);
    maxLoopGap = 0;
  }
}