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编写安全的 ISR

让中断处理程序保持简短，并使用 volatile

编写安全的 ISR 是 CoddyKit 上的免费 Arduino & IoT Academy 课时。这是第 3 节课，共 4 节。你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。这是 Arduino & IoT Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Arduino & IoT Academy 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

A Special Function

An ISR, or interrupt service routine, is the function that runs when an interrupt fires. It has rules that ordinary functions do not.

Keep It Short

The golden rule: make your ISR as short as possible. The main program is paused while it runs, so finish fast and get out.

Do the Heavy Work Later

Inside the ISR, just set a flag or bump a counter. Let the loop do the slow work like printing or math once it sees the flag.

void myISR() {
  pressed = true;
}

Shared Variables

An ISR and your loop both touch the same variable. The compiler may not expect it to change behind the loop's back, which causes subtle bugs. 🐞

The volatile Keyword

Mark any variable shared with an ISR as volatile. It tells the compiler the value can change at any moment, so always reread it.

volatile bool pressed = false;

No delay Inside

Never call delay in an ISR. The timing that delay needs is itself paused during an interrupt, so it simply will not work.

Serial Is Risky Too

Avoid Serial.print inside an ISR. It relies on interrupts that are blocked while your handler runs, so output can stall or garble.

millis Freezes

Inside an ISR, millis stops advancing because its background counting is paused. Read elapsed time in the loop, not the handler.

Handle the Flag in Loop

Back in the loop, check the flag, act on it, then clear it. This is where the real response safely takes place.

if (pressed) {
  pressed = false;
  handlePress();
}

Reading Multi-Byte Values

When the loop reads a multi-byte volatile value an ISR updates, briefly disable interrupts so you get a clean, unsplit number.

noInterrupts();
long c = count;
interrupts();

Why These Rules Matter

Follow these rules and your ISR stays fast and predictable. Break them and you get freezes, lost data, or values that never seem to update.

Quick Check

Why must a variable shared between an ISR and the loop be marked volatile?

Recap

You learned to keep an ISR short, mark shared data volatile, skip delay and Serial, and do the real work back in the loop. 🎉

常见问题解答

「编写安全的 ISR」课时是免费的吗？

是的 — 「编写安全的 ISR」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Arduino & IoT Academy 课程的其余内容，请升级到 CoddyKit PRO。 Arduino & IoT Academy 课程共包含 4 节课。

「编写安全的 ISR」这节课中我会学到什么？

让中断处理程序保持简短，并使用 volatile 你通过在浏览器中直接运行的动手代码来练习 Arduino & IoT Academy，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 Arduino & IoT Academy 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Arduino & IoT Academy 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。这是第 3 节课，共 4 节。

「编写安全的 ISR」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 Arduino & IoT Academy 课中编写并运行代码吗？

能。每节 Arduino & IoT Academy 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

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