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CH340 driver - make Windows see your USB-serial adapter

The CH340 is the USB-to-serial chip on most Arduino-compatible boards, ESP8266/ESP32 modules and cheap USB-serial cables. Without its driver, Windows shows an unknown "USB2.0-Serial" device and no COM port appears - so nothing can talk to the board. The fix takes five minutes.

Fix it automatically

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Quick answer

The board needs the small CH341SER serial driver - one installer covers both CH340 and CH341. Once it is in and the board replugged, a USB-SERIAL CH340 (COMx) entry appears under Ports in Device Manager. The button above finds the driver automatically; the manual route is in the steps below.

Symptoms - how this problem looks

Device Manager shows "USB2.0-Serial" with a yellow triangle
No COM port appears when the board is plugged in
Arduino IDE shows the port grayed out or missing
Windows plays the connect sound but nothing is added
Code 10 or Code 28 on the unknown device
The board worked on another PC but not on this one

Why it happens

Windows has no inbox CH340 driver

Unlike FTDI chips, the CH340 driver is not always bundled with Windows - especially on clean installs the device stays unknown until the driver is added.

Charge-only USB cable

Many micro-USB cables carry power but no data. If nothing at all appears in Device Manager, the cable is the first suspect - not the driver.

Clone chip quirks

Some very cheap boards carry imperfect CH340 clones that only work with specific driver versions - the current WCH driver handles most of them.

An old driver version is stuck

A years-old CH341SER installation can conflict with the current one; removing it first gives the new driver a clean start.

The fixes, in order

1. Let Windows Update try first

  1. Plug the board in, open Settings, then Windows Update, and select Check for updates.
  2. Also check Advanced options, then Optional updates, then Driver updates.
  3. If "USB-SERIAL CH340" appears under Ports in Device Manager afterwards - done.

2. Install the official WCH driver (the reliable route)

  1. Go to the chip maker's site wch-ic.com (also reachable as wch.cn), open the Downloads section and get CH341SER.EXE - the Windows driver for CH340 and CH341 chips.
  2. Run the file and press Install. If it reports "driver install failure", unplug the adapter, press Uninstall, then Install again, then replug.
  3. Replug the board and open Device Manager - under Ports (COM & LPT) you should see USB-SERIAL CH340 with a COM number.

Stay safe: Download the driver only from the chip maker or your board vendor's documentation. Random driver portals bundle old versions and extra software.

3. Point Device Manager at the driver manually

  1. If the device still shows as unknown: right-click "USB2.0-Serial", select Update driver.
  2. Choose "Browse my computer for drivers" and point it at the folder where CH341SER unpacked (or press "Let me pick" and select the CH340 entry if listed).
  3. Confirm and replug the adapter.

4. Verify the COM port and finish the setup

  1. Note the COM number in Device Manager (for example COM5).
  2. In Arduino IDE select that port under Tools, then Port, and try uploading a sketch.
  3. If uploads fail at the right port, lower the upload speed in the IDE or try another USB port - front-panel ports and hubs are less reliable than rear ports.

Where the manual route gets fiddly: it only works when you land on the exact model page and pick the right package for your Windows on the first try - and vendors list several near-identical downloads per model, with the scan or utility half often shipped separately. Driver Updater does the matching for you: it identifies the hardware and installs the current driver in one pass, with a backup before the change.

Download Driver Updater Downloads Outbyte Driver Updater for Windows. Scan and results are free.

Frequently asked questions

CH340, CH340G, CH340C, CH341 - do they need different drivers?

No - the same WCH CH341SER package covers the whole family. The letter suffix only marks packaging and crystal differences on the chip itself.

Windows shows Code 10 for the CH340 device. What helps?

Uninstall the device in Device Manager, run the WCH installer's Uninstall button, restart, then run Install and replug. If Code 10 persists, test another cable and USB port - and try the board on a second computer to rule out a dead chip.

Is the CH340 driver safe for Windows 11?

Yes - the current WCH driver is signed and works on Windows 11, 10, 8 and 7. Signature problems only affected very old driver versions.

The automatic route, whenever you are ready

Outbyte Driver Updater scans the PC and shows what it found - then waits. Nothing is applied without your OK, and every change can be rolled back.

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