Troubleshooting

Troubleshooting

I see strange characters instead of nice boxes

Cause: The terminal is not using UTF-8.
Fix: Enable UTF-8 / Unicode in the terminal settings. Try another font. See Choosing a Terminal Program.

Everything is one color / no color

Cause: The app ignores ANSI colors.
Fix: Use PuTTY, a modern serial monitor with ANSI enabled, or a telnet client that supports colors.

“Port busy” / upload fails after opening a terminal

Cause: Two programs opened the same COM port.
Fix: Close the terminal (and IDE Serial Monitor), upload, then reopen the terminal.

Mouse clicks do nothing

Expected on many USB-serial terminals (especially PuTTY).
Fix: Use Enter, Space, or arrow keys. See Keyboard and Mouse.

Blank screen after plugging USB back in

Try: Wait a moment — several examples redraw when they detect a USB reconnect. Press the board reset button. Re-open the terminal at the correct baud.

Baud rate confusion

Examples	Baud
Most Serial demos	9600
ESP Wi‑Fi control	115200

Mismatch = garbage text.

SD card example will not start

• Check CS pin (default 4)
• Confirm wiring and 5 V / 3.3 V level compatibility
• Use a Mega-class board if Uno runs out of memory
• See Example: ANS files

Wi‑Fi never connects

• Credentials
• 2.4 GHz vs 5 GHz
• Timeout messages on Serial (Network terminal waits ~20 s)
• See Network and ESP Boards

Still stuck?

1. Re-read the example page for your sketch.
2. Note board, terminal app, baud, and library version.
3. Open a Question or Bug report.