USB CH340 Driver Problems

Many microcontroller boards used for grbl and grblHAL use a CH340 chip to connect to the computer’s USB interface. Just recently (Dec 2024), several users of the CNC Foam cutter reported problems. These included

  • DROs (digital readouts) are blank but the board is connected
  • g-code is not sent to the controller, which seems to be paused.
  • jogging controls send the commands but nothing happens. The DRO stay at zero
grbl hotwire
Jog command sent but DRO show 0.00

The genuine Arduino Mega 2560 boards do not have this issue because they don’t use this chip. Most of the boards from China do.

The problem

I even experienced this myself, I suspected a Windows Update was the issue. After some investigation, Windows Update updated the CH340 driver to version 3.9. This version didn’t work with the microcontrollers using the CH340 chip.

The Solution

After days of debugging GRBL HotWire, I implemented a more reliable way to communicate with the USB interface, as recommended by ChatGPT. I used Jason Curl’s DLL from RJCP.DLL.SerialPortStream.

This solved the issue! The updated software is now available for download. Big thanks to Jason

Icon

GRBL HotWire 6.25 (XYZA) 767.91 KB 247 downloads

This update addresses the problem with the CH340 driver update installed by Windows…
Download

Alternative Solution

Roll the driver back to a version before 3.9. From Device Manager follow the screenshots below with your microcontroller connected

If you can only see the 3.9 driver then install an earlier version from this link https://learn.sparkfun.com/tutorials/how-to-install-ch340-drivers/all#drivers-if-you-need-them and then repeat these steps.

  • Step1
  • Step 2
  • Step 3
  • Step 4
  • Step 5
  • Step 6 – Select Next
  • Step 7

A computer restart may be required to complete the rollback of the driver

If the problem happens again it’s probably a Windows Update that has been applied. There are ways to prevent this but it involves editing the registry. Do this with caution.

This link explains how to prevent future Windows Driver Updates https://www.windowscentral.com/how-disable-automatic-driver-updates-windows-10

You may find several CH340 drivers installed as Step 6 above shows. The 3.9 driver is the problematic one and you can remove it by following the instructions here https://help.nicelabel.com/hc/en-001/articles/4413996133009-Removing-drivers-from-Windows-driver-store#removing-drivers-from-windows-driver-store-1-0

Happy Foam Cutting

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