Editing Openai/692da612-aac4-800b-80dd-f1568632e2ff (section)

=== ### ===

Upload this tiny test sketch (you already have working upload):

<syntaxhighlight lang="cpp">void setup() {
  Serial.begin(9600);
  Serial.println("SERIAL_OK");
}

void loop() {
  // nothing
}

</syntaxhighlight>

After upload, open Serial Monitor (Ctrl+Shift+M).
* Set baud at the bottom right to 9600.
* Set No line ending (doesn't matter for this test).

If you see SERIAL_OK → Serial works. If not, continue.

===== Top menu → Tools → Port → select the port that says Arduino Uno (COM6) or the COM number shown in Device Manager. =====
If multiple COMs, choose the one that matches Device Manager.

===== Completely close: =====
* Any other Serial Monitor windows
* VS Code (PlatformIO)
* PuTTY / CoolTerm / Python scripts
* Serial plotter instances

Then re-open Arduino IDE and Serial Monitor. Try again.

===== Sometimes Serial Monitor must be opened after upload so it opens the port. =====
Procedure:
# Upload sketch.
# Wait for Done uploading.
# Then open Serial Monitor (Ctrl+Shift+M).

See if output appears.

===== Sometimes DTR/auto-reset timing fails on clones. Do this: =====
# Upload sketch.
# Open Serial Monitor. (Nothing appears.)
# Press the UNO RESET button once.
# Check Serial Monitor — do you get the printed text?

===== - Serial Monitor baud must equal Serial.begin() value. =====
* Try different baud values (9600, 115200) if your sketch uses different.
* Set line ending to No line ending for testing.

===== 1. Power OFF. Place jumper between TX (pin1) and RX (pin0). =====
# Power ON. Open Serial Monitor on COM6 at 9600.
# Type some characters — if they echo back, the USB-Serial interface & driver are OK.
# Remove jumper.

If loopback works but your sketch prints nothing, the MCU may not be sending serial (but you tried blink+serial earlier). If loopback fails, driver/cable/USB-serial chip problem — go to Step 9.

===== Open Device Manager → Ports (COM & LPT) and look at the Arduino entry. Copy the exact name shown (e.g., Arduino Uno (COM6) or USB-SERIAL CH340 (COM6)) and paste here. =====

If it shows Unknown device or has a yellow icon, you need the driver (see step 9).

===== If Device Manager shows CH340 or CP210x or unknown, reinstall the driver: =====
* For CH340 (common cheap clones): search “CH340 driver” and install the Windows driver, then reboot.
* For CP2102: search “CP2102 driver” and install.

If you want, tell me the exact Device Manager text and I will give the exact driver link and step-by-step install commands/GUI steps.

===== Try PuTTY or Tera Term to open COM6 at 9600: =====
* If PuTTY shows the serial output but Arduino Serial Monitor does not, the IDE is the issue.
* If both fail, it's a driver/port issue.

===== Right-click Arduino IDE → Run as administrator, then open Serial Monitor. =====
Sometimes Windows permission blocks access.

===== - Try a different USB cable (must be data cable). =====
* Try another USB port (rear port on desktop).
* Try the UNO on another PC — if Serial Monitor works there, problem is on your PC.

===== Use Process Explorer (Sysinternals): =====
# Download & run Process Explorer.
# Press Ctrl+F, search for COM6.
# It will show which process has the handle. Kill that process (if safe), then try Serial Monitor again.

I can give the download link and exact clicks if you want.