My WIN11 can detect USB Virtual COM Port, but my coworker cannot

Andrew_Sung · ‎2025-08-10

Hello everyone,

This is my first post here, so if there's anything wrong with the way I've formatted or presented it, please feel free to let me know.

My current task involves switching from USB HOST to USB CDC. I used CubeMX to generate the necessary USB CDC-related files and integrated them into my original program.

On my PC, the program works as expected and is recognized correctly as a COM port.

However, on my coworkers' PCs, the device is not recognized as a COM port.

Both our PC are win11, and after checking, win11 seems no longer requires the installation of the STM Virtual COM Port driver.

Is there anything we can do to further clarify or resolve this issue?

Andrew Neil · ‎2025-08-29

@Andrew_Sung wrote:
even on the same laptop, different USB ports can provide different power levels.

Indeed - that's why "try a different port" is standard advice in these situations; eg, see here.

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

LCE · ‎2025-08-29

USB ports on desktop PCs and laptops behave so different, it's terrible...

Some 2.0 ports actively limit the current to the specified 500 mA (and without "complaining" to the OS, this is probably the worst, because itmight cause some weird behaviour).
Some turn the power off, some tell the OS that there's a power problem, some deliver 1000 mA without complaining, ...

So it makes absolutely sense to know and control the current you need from USB.

@Andrew_Sung I'm curious, how high is the peak current you actually draw from USB?