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I am a pretty newby to this forum, please be patient. I purchased a load variable kit yesterday, and I assembled it as indicated into the hookup guide, but when I plug the USB cable into my laptop, windows doesn't recognize the device and so I cannot communicate with the board using the USB-COM interface :cry: .
Please could anyone give me support?
Hi. Thanks for writing in onto the SparkFun forums. I apologize for the late reply here.

It might be your Windows OS, or perhaps there may be an issue with the board. If you could provide front and back photos of the soldering on the board if this is still an issue we can look into it.

Dear sir or madam,

I have the identical problem with my KIT-14449. Plugging in the unit searches for but does not find the USBUART device driver. I purchased this unit 2019-03-16 with order # 5466877.

I am running it on Window 7 64 Ultimate SP1 with all updates .

I tried loading drivers from these sources without any luck:

-- loaded the Arduino SAMD (M32) board support package. It installed without error,
but I got the same nissing USBUART error message when I plugged in the unit.

-- I loaded the Cypress Windows Certified USB UART driver 'CypressDriverInstaller_1.exe' from: ... art-driver
The Cypress driver installed fine but I still could not connect to the unit.

I have a Masters Decree from Stanford with 30 years of experience so I believe I am capable of soldering the 2 components that must be soldered to the board. I have attached links to pictures of the top and bottom of my unit.

Please send information on where to download the device driver for this product.


Kenneth West
I have more information on my problem using the Sparkfun Variable Load Kit (KIT-14449).

I found that the device will connect to the Windows 10 laptop I have. The problem appears to be that Windows 7 64 bit is missing the userser.inf driver information file although it does have both the 32 and 64 bit version of the core usbser.sys driver. The problem is that my Windows 7 system is next to my workbench and that's where I need the Variable Load.

Ironically, the Variable Load is also supported by the Raspberry PI Zero W. Fortunately, I have a PI Zero on my workbench that I can use to connect to the device. It is not ideal but it does work.
Interesting. I figured the issue may have been related to the operating system. I was actually anticipating that the issue would be associated with Windows 7. Microsoft pushed an update recently that seems to have broken a lot of drivers for several of our products including all of our devices that use a SAMD21 chip.

I am glad to hear the Load Variable Kit works on Windows 10 and the Pi Zero W. Sorry to hear about the inconvenience of the situation.

I will report this issue to our engineers. Hopefully, we can figure out a fix soon.