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UART speed change, USB, WIn10

Pierre-Yves BERGER
Associate

Hello,

I have an application developed on top of a Nucleo Board (F446RE). This application uses the STM32 serial lines connected to the STLink MCU and accessible on a computer through an USB VCP.

The F446RE Uart is initially set @ 921kbps and is working fine. While the application is running, I sometime need to change the UART speed to 115kbps or even 9.6kbps.

This works fine on most computer I have used (win7, Win8, Linux, ...), I mean on the computer when i change the terminal (TeraTerm speed, I can see communication works well).

Lately I stumbled upon a strange issue with a couple of Win10 PCs:

- Win 10 PC use the Microsoft Win10 USB VCP driver

- On one PC when I change the speed from 921k to 9.6k it works, but when i change from 921k to 115k it doesn't (the PC still sees the VCP but no data exchange is possible).

- On the other PC when I change the speed (whatever speed) the VCP either disappear (rarely) or the VCP doesnt work anymore (no more data seen)

- Tests were done with a simple term software (TeraTerm)

Any clue where it can come from, it is pretty annoying and probably link to either the STLink firmware (I use latest) or the Win10 driver - or a combination of both.

Thanks for the help, 

PyB

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