General Category > Connected meters (SQM-LE/LU/LR/DL)

FTDI driver installation problems


For some strange reason a recent problem with the installation of the FTDI USB driver for Windows has cropped up. The problem may something to do with cancelling the automatic installation of the FTDI USB VCP driver when connecting a new SQM USB device.

The Windows registry saves old versions and old COM port assignments, and can only be cleaned up with a custom utility provided by the driver manufacturer (FTDI). Here are the steps to solve that problem:

Install this FTDI "CDM Uninstaller" utility:

The detailed instructions for its operation are here:

Here is a summary of the instructions:

* Remove/unplug the SQM-LU device
* Start up the CDM uninstaller program
* Press - Add
* Press - Remove devices
* Wait 5 minutes or so until complete
* Close
* Re-insert SQM-LU device
* Wait 5 minutes or so for Windows to install driver and port. If Windows fails to install the driver, it will have to be manually installed with the "setup executable" available from (see the comments column on that page for the latest link).

Installing Windows FTDI driver manually (preventing auto-update)

Just recently, Microsoft seems to have stopped providing FTDI drivers automatically for Windows 7 (and possibly other versions).

This can be a problem because connecting an FTDI device to the USB port usually initiates an automatic check for updated drivers and failure to find such a driver at Microsoft results in a failed driver installation.

You can turn off automatic updates to prevent this as follows:

* Open the: Control Panel -> System Security -> Windows Update
* Select Change settings
* Deselect Recommended updates
* Press OK
You can now manually install the FTDI driver from

Then plug in the SQM-LU device.

Clearing Windows COM list

After installing different FTDI devices in Windows, the system fills up with COM port numbers.

You should prevent auto update as identified in the previous post, then ...

If you are very careful, it is possible to clear off all the "used" COM ports by following the instructions at this link:


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