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CTS signal on USB CDC

Question asked by Willem La Grange on May 15, 2018


I need to send the CTS status from my target hardware to the Virtual com port driver in windows, USBser.sys.

I have managed to do all the other handshake signals (DTR, RTS, DCD and DSR) working except CTS. Apparently there is no provision for CTS in USBD PSTNv1.2 form and there seems to be a bug in the windows USBser.sys driver. The CTS signal status get set whenever you set the DSR signal but then you cant clear the CTS signal again. I am not using CTS for my hardware flow control (It is not necessary) but the program that needs to connect to the VCP driver uses the CTS signal in a login process together with DSR


Does anyone have a clever idea how to manipulate the CTS signal in the CDC class?

Your input would be highly appreciated.