使用 pulseIn 测量回波时间
测量回波脉冲并换算为厘米
使用 pulseIn 测量回波时间 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。
Fire the Pulse
To take a reading you first send a clean trigger pulse. The HC-SR04 expects a short HIGH on Trig to start a new measurement.
Start From Clean
Set Trig LOW for a couple of microseconds first. This clears any leftover state so your trigger pulse is crisp and reliable.
digitalWrite(trigPin, LOW);
delayMicroseconds(2);A Ten-Microsecond Pulse
Now drive Trig HIGH for 10 microseconds, then back LOW. That exact width is what the sensor needs to launch its ultrasonic burst.
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);Meet pulseIn
The function pulseIn waits for a pin to go HIGH, then times how long it stays HIGH, returning that duration in microseconds.
Time the Echo
Call pulseIn on the Echo pin watching for HIGH. The number it returns is the full round-trip time of your sound pulse.
long duration = pulseIn(echoPin, HIGH);It Waits for You
pulseIn is blocking: it pauses your sketch until the echo arrives or times out. For simple distance projects that pause is perfectly fine.
Turn Time Into cm
Multiply the duration by the speed of sound and divide by two. The result is a clean distance in centimeters.
float cm = duration * 0.0343 / 2;Where That Number Comes From
Sound travels about 0.0343 cm per microsecond. That constant is just the speed of sound rewritten in units that match pulseIn.
Print It Out
Send the value to the Serial Monitor so you can watch the distance change as you move your hand toward the sensor.
Serial.print(cm);
Serial.println(" cm");Give It a Breather
Add a short delay between readings, around 60 milliseconds. This stops one echo from leaking into the next measurement.
delay(60);Handle a Timeout
If nothing reflects, pulseIn returns zero. Checking for that lets you skip junk readings instead of printing a false distance.
Quick Check
Think about what pulseIn measures.
From Pulse to Distance
Trigger, time with pulseIn, then convert and print. You can now read range in code. Next, make the sensor do something useful. ✅
常见问题解答
「使用 pulseIn 测量回波时间」课时是免费的吗？
是的 — 「使用 pulseIn 测量回波时间」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。
「使用 pulseIn 测量回波时间」这节课中我会学到什么？
测量回波脉冲并换算为厘米 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。
「使用 pulseIn 测量回波时间」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。