Serial.begin และอัตราบอด

Your board can talk to your computer over the same USB cable that powers it. That conversation is called Serial communication. 🔌

A microcontroller has no screen, so Serial is how you peek inside it. You print messages and watch them live on your computer.

Before any printing, you must open the connection with Serial.begin(). You do this once, inside setup().

The number you pass to begin is the baud rate: how many signal changes per second travel down the wire. It sets the speed of the chat.

A baud rate of 9600 is the friendly default. It is slow but rock solid, so most beginner sketches start there.

You can go faster, like 115200, to stream lots of data without lag. Higher speed means more bytes per second.

Here is the golden rule: the baud rate in your code must match the one set in the Serial Monitor, or you get garbage characters.

If your monitor shows weird symbols like ⸮⸮⸮, do not panic. It almost always means the baud rate on the two sides is different.

Put Serial.begin() in setup(), not loop(). You only open the channel once, then it stays open for the whole program.

On some boards you add while (!Serial) to pause until the USB port is truly ready before you start printing.

Choose a baud rate and stick with it across your whole project. Mixing speeds between sketches is the most common Serial headache.

You set Serial.begin(9600) but the Monitor shows random symbols. What is most likely wrong?

You opened a USB chat with Serial.begin() in setup, learned that baud rate sets the speed, and that both sides must agree on it. 🎉