发布传感器主题
将读数发送到指定名称的主题
发布传感器主题 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。
Sending Data Is Publishing
Once connected, sharing a reading is one call. You publish a value to a topic and the broker delivers it to subscribers.
Choose a Clear Topic
Pick a descriptive topic path like home/garden/soil. Good names make a growing system easy to read and route.
home/garden/soil/moistureThe publish Call
The basic form takes a topic and a message. Both are simple strings, so MQTT does not care what is inside the payload.
client.publish("home/garden/temp", "23.5");Payloads Are Just Text
A payload is a plain byte string. You decide its meaning, whether it is a number, a word, or structured data.
Numbers Need Converting
Sensor readings are often floats. Turn them into a string first with dtostrf or String() before you publish.
char buf[8];
dtostrf(temp, 4, 1, buf);
client.publish("home/temp", buf);Send Structured Data as JSON
To bundle several values, format the payload as JSON. One message can carry temperature and humidity together.
client.publish("home/dht", "{\"t\":23.5,\"h\":55}");Do Not Flood the Broker
Publishing thousands of times a second wastes power and bandwidth. Add a sensible interval so messages stay useful.
Time It with millis
Use millis() instead of delay to publish every few seconds. Your device stays responsive while it waits.
if (millis() - last > 5000) {
last = millis();
publishReading();
}Retain the Latest Reading
Add a retain flag so the broker stores the most recent value. New dashboards then show data the instant they connect.
client.publish("home/temp", buf, true);One Topic Per Quantity
Give each measurement its own topic, like .../temp and .../humidity. Clean separation keeps subscribers simple.
Confirm It Worked
The publish call returns true on success. Log it, or watch with a desktop MQTT client, to be sure data left the board.
Quick Check
You want a new dashboard to immediately show the last temperature, even before the sensor publishes again. What helps?
Recap
You learned to publish sensor data: convert values to strings, pick clear topics, time sends with millis, and retain the latest. 🎉
常见问题解答
「发布传感器主题」课时是免费的吗？
是的 — 「发布传感器主题」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。
「发布传感器主题」这节课中我会学到什么？
将读数发送到指定名称的主题 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。
「发布传感器主题」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。